Cyclone and Dust Collection Research


Welcome to the updated Cyclone and Dust Collection Research web pages.
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Cyclone & DC Testing

  1. Summary

    My professor and engineer friends tested most brands and sizes of small shop vacuums, dust collectors, cyclone separators and air cleaners, but I was blocked from being able to share. All our testing was done with tightly controlled standards and equipment similar to what we use in university engineering tests. We used professional freshly calibrated and certified digital meters. We followed the airflow test standards. We only tested units purchased at local outlets without advising the sellers these units were to be used for testing. The results went up on these pages and within a week had to be taken down.

    The test results had to be taken down because three of the bigger small shop dust collection vendors tied me up with litigation. I spend thousands on attorneys who all assured me we would win eventually, but if I did not remove these test results and vendor names, these vendors would be granted a court order to force me to pull down my web pages for the years they could drag out these nuisance suits. Moreover, each of these suits would cost at least $25,000 to defend and I do not have a spare $75,000 or more to invest in these suits. Three different woodworking magazine editors shared they had the same problem where the big name vendors forced them to omit the test results and to change their testing to make certain equipment appear to perform far better than it does in real use. So if you are looking for accurate thorough test results on small shop vacuums, dust collectors, cyclones and air cleaners, you are not going to find them.

    This web does share some good summary information and partial results from some of the more credible magazine testing. Sadly these results are all incomplete because the vendors refused to allow the magazines to do full testing with apples to apples comparisons. I worked hard with Fine Wood Working magazine to thoroughly test small shop dust collectors. The vendors managed to kill the filter tests and required use of oversized test pipes and recording airflows that will quickly burn up motors as though they were valid. Worse, the vendors killed the second part of our articles that tested small shop cyclones. Although they found no misinformation or testing flaws, two of the largest vendors were so upset at how poorly their equipment worked that it actually increases health risks that they killed the article by threatening to withdraw their advertizing if the article was published.

  2. Foreword

    This page still shares summary results after my associates and I tested most current small shop dust collectors, cyclone separators and air cleaners. We tested both airflow and fine dust separation. All of this testing was done with tightly controlled standards similar to what I would use in university engineering tests. We did our testing with expensive freshly calibrated and certified digital meters. There were none of the games played like most magazine apple versus orange comparisons where they tested the systems with different or oversized test pipes, special bell shaped test ends that falsely magnify airflows, the nonsense of running blower motors at far over their rated amperage, or use of meters that don't even have the ability to measure the airflow or particle size ranges being tested. We also only tested units purchased at local outlets without advising the sellers these units were to be used for testing. In reviewing prior magazine tests we discovered that some vendors provided oversized blowers and motors that they had carefully relabeled to make the test units appear the same as those they sell.

    Since I started testing in early 2001, little has changed because the vendors continue to do little to nothing in terms of improving their shop vacuums, air cleaners, dust collectors or cyclones except in some cases they use better filters. Frankly, our ongoing testing shows the vendors just keep copying each other and selling the same "chip collection" designs that we already know pass dangerously high amounts of airborne fine dust.

  3. Introduction

    Rather than just start testing, we took the time to understand what this industry recommends. My Dust Collection Basics pages show you exactly what the experts found we need for good dust collection. The experts found good dust collection requires us to use good hood designs (see my ducting page) that block, control and capture the fast moving air streams, then we need ample airflow where most small shop stationary tools get fairly good chip collection with about 350 cubic feet per minute (350 CFM) and need about 1000 CFM for good fine dust collection; and then we need to get rid of the fine dust by either blowing it outside or filtering. The medical experts say we need filters that provide at least 99% filtration of all particles sized 0.5-microns and larger and they recommend that we use HEPA grade filters that provide 99.97% efficiency on particles sized over 0.3-microns. The major filter makers say after removing all but the airborne dust woodworking still makes so much dust that we must provide a minimum filter area. There are two types of filters used with woodworking, the all polyester felt type filters and the polyester cellulose blended filters. Polyester filters typically cost about double what the blended filters do to purchase. Filters made from all polyester material are thick and water proof so they can be washed. Washing redistributes the fine filter strands to close most of the openings which restores most of the filter performance. As a result all polyester filters can be washed about three times before they need replaced. In spite of the reduced overall long term filter cost most commercial shops choose to use the blended filters that they throw away when worn out because of the considerable down time and staff costs to wash filters. Because the all polyester filters are typically much thicker, we need just about half the total surface area as the blended filters. The filter makers are very clear that for woodworking dust loads we need at least one square foot of blended filter area for every 4 CFM of airflow and really should have one square foot for every 2 CFM of airflow to minimize filter cleaning, maximize filter life, and maximize airflow. Most small shop vendors provide about one square foot of all polyester filter for every 10 CFM of airflow or only one square foot of blended filter for every 5 CFM of airflow. By giving us too little filter area what happens invariably is as the filter seasons airflow drops first too low to get good fine dust collection then too low to get good fine dust collection.

    This page started as a collection of comments made by users of the various small shop dust collection options and it worked poorly because the information was too emotional without any facts to support the opinions. Many of those who were the strongest supporters of a particular dust collection solution soon became even stronger speaking out against those same units within a year or two.

    This emotional issue became even more heated when my university engineering instructor friends and I started to share the results of our testing. Our testing continues to show all small shop dust collectors, cyclones, air cleaners, shop vacuums, and filters are advertised with maximum airflow and filtering claims far beyond their real performance when used in our shops. Almost all came with too open filters and moved too little air to provide the fine dust protection their advertising claims. The terrible airflows and filtering our tests found explain why government testing finds almost all small shops have airborne dust levels well above the levels that forced OSHA to put in place its 1989 allowable limits for airborne dust.. Small shop vendors have known about these problems since at least 1994 but with no government requirements and no push from us as their customers, they keep selling the same tools and dust collection equipment that does not protect our health. The only fine dust protection we are going to get is what we provide ourselves. We must figure out what we need then buy and assemble the pieces ourselves to build our own working fine dust collection solutions. I recommend starting with my Dust Collection Basics web page to help you decide what level of dust collection you want followed by using the Deciding Needs page to help you understand what equipment you need.

  4. Dust Collection Evaluation

    We evaluated each dust collection solution based on its airflow and filtering. We need ample airflow to provide the level of dust collection needed. Although all of the experts recommend placing and venting our dust collection systems outside, if we instead choose to filter, then the filter must be fine and large enough to work for us. An undersized filter clogs too quickly, needs constant cleaning, and rapidly fails. A too open filter does not provide good health protection.

    1. Small Shop Dust Collection Product Overview

      Sadly, our small shop vendors have long made their livelihoods by copying and downsizing larger commercial tools, having these tools built overseas by minimal cost labor, and then selling to small shop woodworkers. Most of these vendors do a terrible initial job of copying and need years to slowly iterate through many changes to end up with a viable product. The better of these vendors follow the Japanese lead with automobiles and continue to refine their products until they actually end up with a superior and more reliable end product. The less reputable vendors stop making changes when they have products that work for the lowest possible price.

      Every dust collector and cyclone we tested came without the information on safe use. Not one single small shop dust collector or cyclone came with a recommendation that these units are not fire and explosion certified, so will fail a fire marshal inspection and home insurance policy inspections if installed inside our shops. To pass these inspections these units must be placed outside in their own fire proof covered area behind an explosion proof barrier or wall. This requirement is actually excellent advice and the best way to use these units to avoid serious fine dust problems. None discussed the reality that they are a waste of time if you don't first make sure your hoods control and capture the fine dust. None came with any information that explains the need to upgrade most tool hoods to get ample chip or fine dust collection. None even mentioned any of the health concerns related to fine dust or came with any recommendation that you should always wear a good NIOSH dual cartridge respiratory mask plus protective clothing whenever cleaning or changing filters. Most came with fine filters, but gave no clue as to when we need to change our filters or any of the normal filter preparation that should be done. None came with any warnings at all that their systems passed significant fine dust and that it is imperative that shops be vented while these units run with a good exhaust fan blowing outside not just when the unit runs but also for about 30 minutes afterward. The only two cyclones that came with ducting advice, provided advice appropriate to large facilities that use huge blowers ample to collect from all machines working at the same time with no blast gates. No 5 hp and smaller cyclone that we tested had enough airflow to collect from more than one stationary tool working at a time. As a result these complex ducting plans with huge main and tiny down drops created a serious problem where when collecting from tools with smaller down drops the air in the mains fell so low that main vertical runs plugged and the horizontal runs built up dust piles. Dust piles in our ducts pose a very serious fire hazard as any spark can get blown into a serious fire, plus when these piles break loose they slam down our duct hard enough to break apart our ducting joints, go right through cyclones to ruin blowers, and ruin filters.

      All dust collectors we tested came with inappropriate two, three, or four way adapters. No dust collector under 3 hp moved enough air to provide good fine dust collection from more than one machine running at a time, yet every 1.5 hp and larger dust collector came with an inlet cover that split a 5" or 6" connection into two or three smaller diameter connections. The problem here is the normal material handling pressure blowers used in dust collection only generate a limited amount of pressure. These standard blowers can only pull 349 CFM through 4" diameter duct, 545 CFM through a 5" diameter duct, and 785 CFM through a 6" diameter duct. To move our required 1000 CFM airflow to get good fine dust collection with these sized blowers we need at least 7" diameter duct. To get that same 1000 CFM needed for good fine dust collection through smaller sized duct, we must use special blowers with oversized impellers that generate much higher than normal pressures. These 4" ports so kill the airflow they are useless for good fine dust collection unless you hook at least three to each stationary small shop tool. It is far better to use a 7" diameter main and down drop then split that into a pair of 5" duct. I found the 7" diameter duct, splitters, and connections so difficult to find, expensive, and bulky to work with that I designed my blowers to generate far higher pressures permitting use of 6" diameter mains and down drops.

      • All the major small shop vendors advertize maximum instead of the working airflows. Relying on these maximums ends up with about half the airflow we need because maximum airflows are just about double real working airflows due to the resistance of our tool hoods, ducting, separators, and filters. Worse, all of the major vendors except for Delta, Jet, and Powermatic even exaggerated these maximum airflows.

      • Many import vendors gravely exaggerated motor horsepower. This is similar to many vacuum cleaner makers who claim as much as 6.5 hp from a unit which plugs into a U.S. standard 120 volt 60 cycle power outlet that will only support about 1.5 hp.

      • All the cyclone vendors except Clear Vue Cyclones gravely misrepresented the separation ability of their cyclones. Instead of saying how well their cyclones work, they claim separation values after running the cyclone outlet air through a fine filter. This is particularly bad because all except Clear Vue let 100% of the airborne 30-micron and smaller particles pass right through the cyclone. Woodworking makes so much airborne dust that this means filters rapidly clog, need constant cleaning, and cleaning quickly ruins filters.

      • Every major brand of dust collector, cyclone and air cleaner gravely misrepresented the protection offered by their filters because they used outdoor filter ratings instead of indoor. As a filter ages it seasons which means it builds up a cake of dust in the filter pores that does not come out with normal automated shaking type cleaning. This trapped dust known as a cake blocks air movement and improves filtering. Because of this blockage, most engineers build systems that use the fully seasoned filter resistance levels to properly size their filters. Since by law in almost all areas dust collectors and cyclones must be put outside behind explosion proof barriers, most air engineers also use the fully seasoned filtering level when they specify filter performance. This causes a major problem because a fully seasoned filter provides roughly twenty times better filtering than a clean new filter, but even with this improved filtering fully seasoned filters constantly leak and replace the finest dust trapped in the filter pores. It also takes about a year for a typical small shop filter to fully season. During and even after seasoning our filters constantly pass through much of the unhealthiest invisible dust into our shops for us to breathe. This dust leakage is why the American Society of Heating Refrigeration and Air-conditioning Engineers (ASHRAE) who set the standards for indoor filter testing requires testing indoor filters when clean and new. The bottom line is even the advertized "fine" filters turn our air cleaners, dust collectors, and cyclones into dust pumps that fill our shop air with huge amounts of fine invisible very unhealthy dust every time we turn them on.

      • Our small shop vendors provide no recommendations or warnings about the fire and air quality safety dangers of placing our dust collectors or cyclones inside. Most small shop users put their dust collectors and cyclones inside and use them with fine filters creating fire risks.

      • Most traditional tools copy older commercial tools with no or poor hoods, ports and internal air channels that are not big enough to support good chip collection and are far too small for good fine dust collection. Even tools copied that have good chip collection still do not support movement of enough air to collect the fine airborne dust. To get good fine dust collection with these traditional tool designs we almost always have to redo our tool hoods, ports, and even internal air channels.

      • All shop vacuums, dust collectors, and cyclones except for the Clear Vue that we tested freely passed all of the airborne dust right into their filters. Wood dust contains many sharp edges and points that cut and tear open the filter pores as the dust gets forced through our filters. Cleaning forces these sharp edged dust particles through out filters which is why cleaning rapidly wears out filters. Woodworking makes so much airborne dust that when we direct almost all of this airborne dust into our fine filters that unless we have huge filters they quickly plug and need constant cleaning so rapidly wear out. Additionally filter plugging kills our airflow and increases pressure enough to also force dust through our filters increasing wear and shortening filter life. In large commercial shops this damage is enough that most must replace their fine filters every three months of full time use. So most small shop dust collectors and cyclones are not appropriate to use with the fine filters that most vendors now provide. Instead they should be used with the traditional older 30-micron more open filters and vented outside.

      • Rather than use large fine enough filters that are expensive and would cause constant customer upset over the constant need for cleaning and replacement, most small shop vendors sell much more open filters that freely pass the finest unhealthiest invisible dust. This makes for far less filter plugging, cleaning and replacement, but gives a false sense of security. We end up filling our shops with so much fine invisible dust that even in the cleanest looking shops just walking around raises enough dust to fail an air quality check without doing any woodworking. At these levels many get ill quickly. This is exactly what happened to me and left me in the hospital.

      • To ensure customers are not unhappy because of the filter cleaning and replacement issues, most small shop vendors simply use far more open filters that freely pass the invisible unhealthiest dust. Letting the fine dust right through that tends to clog our filters gets rid of this cleaning and constant filter replacement problem, but put us as woodworkers at grave risk.

      • A traditional dust collector needs at least a 3 hp motor and a traditional cyclone design needs at least a 4 hp motor to move the 1000 CFM that the air engineers have established as a minimum to get good fine dust collection at most small shop stationary tools. Most small shop dust collectors and cyclones advertised to provide good fine dust collection have blowers and motors too small to move the required airflows.

    2. Blower Testing

      This copying traditional tool approach used by all the small shop vendors made for a wide variation in blower performance which surprised most of us doing the testing. We found an inconsistent mess when it comes to small shop blowers used on shop vacuums, air cleaners, dust collectors and cyclone systems. Blower technology is very mature. Any diligent student can easily look up the engineering to turn out excellent blower designs. Almost every U.S. brand name blower with the same motor speed and same type and sized impeller will deliver near identical performance. Performance is so consistent that those who specify blowers use any vendor fan table and will get near identical blower performance regardless of brand. We found the higher priced imports that have been in use for a while tend to work pretty well and deliver almost exactly the same performance as the leading U.S. made blowers. The newer and lower cost imports delivered much worse performance with the worst at less than half what we would expect from traditional blowers. The differences include poorly shaped and formed blower housings, constrictive roughly made inlets and outlets, poor quality motors that really don't deliver advertised power, and roughly made parts and impellers that significantly interfere with airflow. Our testing found almost all lower cost imported blowers whether on dust collectors or cyclones, had many major design, copying, and manufacturing problems built right into each unit. In short, unlike the near identical performance expected from reputable blower makers, out imported shop vacuum, air cleaner, dust collector, and cyclone blowers all delivered varying performance with the best only matching standard U.S. blower performance tables.

      Almost all small shop vendors lie when they advertize 97% to 99% separation efficiency. Without pulling any punches we only found two basic cyclone designs being sold by all of the major small shop vendors. One very squat fat looking cyclone which I am not allowed to name uses its own unique design. This unit was magazine tested to separate much worse than a trashcan separator and even most dust collectors. Our testing found it was even worse than the magazine test reported. All other small shop vendor cyclones are downscaled copies with small variations of the same 1962 New York Dept of Labor, Division of Hygiene Engineering cyclone. Many had serious copying errors. That 1962 cyclone was engineered for venting directly outdoors, not through filters. It requires use of monster blowers that generate huge internal cyclone turbulence to knock the airborne dust from the heavier sawdust and chips. It depends upon gravity to drop the heavier sawdust and chips and simply vents the airborne dust outside. This cyclone consistently provides almost zero percent (0%) airborne dust separation. On average airborne dust makes up 5% of woodworking dust by weight. Additionally, any strings, long shavings, pet hair, and thin strips that get collected which can get into both the downward and upward moving air streams inside the cyclone can blow right through. On average about 2% of the woodworking debris collected consist of these things that go right through our cyclones. Adding 5% for the weight of airborne dust and 2% more for the odd shaped stuff that goes right through cyclones, the best expected separation efficiency of cyclones based on this design is only 93%. Sadly, some of the prior magazine tests reported the 97% to 99% collection efficiencies that these vendors advertize. We found they tested the cyclones by using dust from the bin of a traditional cyclone, meaning the airborne dust and strange shaped pieces were already gone. Our own testing found that instead of 93% efficiency there were so many major design copying errors that most small shop cyclones provide little better separation than typical trashcan separators.

    3. Dust Collector Testing

      Our dust collector testing tested to see if each dust collector moved ample air for good fine dust collection and if it provided ample filtering. The experts determined that most small shop stationary tools will get minimum OSHA air quality if they move 800 CFM, need to move 900 CFM to meet the five times tougher ACGIH air quality standards, and must move a full 1000 CFM if they are going to meet the EPA, European Union and medical recommended standards.

      As expected from our blower evaluations, of all the major advertised dust collector vendors only the Delta and Jet families of companies provided dust collectors that actually moved the maximum airflows they advertised.

      Only Jet and Delta made dust collectors with 1.5 hp motors able to move a real 800 CFM when challenged by the minimal resistance involved in moving a portable dust collector between machines. We found no other vendor who moved this same 800 CFM with anything less than a 2 hp dust collector. All other vendors had so many blower and dust collector design errors and poorly made parts that they needed at least 2 hp motors to move this needed 800 CFM. Sadly, one lower cost import vendor did not move800 CFM with their 3 hp dust collector.

      No vendor moved the 900 CFM or 1000 CFM needed to meet the higher air quality standards with a dust collector powered by anything under a 3 hp motor and 14" diameter impeller.

      We found no dust collector that came with filters suitable for indoor use. Medical experts recommend at least 0.5-micron filters for health protection and for those of us with existing allergies or respiratory problems we should use HEPA grade filters that provide 99.97% collection efficiency on particles sized 0.3-micron and larger.

      Most larger and inexpensive dust collectors come with 30-micron bags that are ideal for venting outside. By definition airborne dust particles are sized under 30-microns so this size filter passes close to 100% of the airborne dust. When vented outside airborne dust vanishes with no visible trace. This also means we spend minimum time cleaning filters and get maximum filter life.

      All of the dust collectors with canister cartridge filters had problems. The cartridges offer far more surface area than the standard bag filters so can provide finer filtering with much better airflow and lowered resistance. I now recommend against cartridge dust collectors because almost all feedback says they just have too many filter problems.

      Although many vendors offering cartridge filtered dust collectors promise less frequent cleaning and provide their units with various flappers, beaters, and even shakers to help keep the filters clean, most find that to be advertising nonsense. The finer cartridge filters need far more surface area than provided to avoid constant plugging, so most of these units become a constant cleaning nightmare needing cleaned every few minutes of operation. Many sharp pointed chips stick in the filter pleats leaving holes in the filters. The constant cleaning and chip holes make for rapid filter wear. And the buildup of fine dust creates pressure problems that force the fine dust to tear through the filter pores opening them rapidly. Most of these cartridges start off passing fine dust, and even those that do not soon freely pass the fine dust also. In short, bag or cartridge, these dust collectors should be put outside with no air returning to our shops. If they are going outside then a good heavy 30-micron polyester felt filter with a fine weave will pass the most air and minimize cleaning overhead. For those who must use these units indoors I recommend making your own conversion starting with a good dust collector that will move at least a real 1100 CFM then adding a good 300 square foot or larger ASHRAE certified fine 0.5-micron filter and using a separation screen to protect the filters from hits from sharp chips. These filters need to be closely monitored and changed as they wear or begin to let the fine dust right through. Please see my DC conversion page for more information.

      The Fine Woodworking April 2006 magazine issue #183 contains an article by Michael Standish titled "Portable Dust Collectors". I helped setup the testing protocols and edited this article. The testing done for this article did much of the testing I am no longer permitted to share that my scientist and engineer friends have done. After six nuisance law suits over my sharing our actual test results, I cannot afford any more litigation. I win every time because what we did is fair, consistent, industry standard testing that is easily duplicated, but winning does not reimburse my legal expenses.

      This article came up with exactly the same conclusions and recommendations that we reached from our ongoing testing. The below graph copied from this article is easy to read and tells us which machines move ample airflow and the answer is none if you are serious about good fine dust collection. Anything above the 400 CFM line and below the 800 CFM line is a good "chip collector", so this graph confirms every dust collector tested provides good "chip collection". Because the testing for this article was well done using a consistent filter that was already "seasoned" we do not have to worry about the overhead of the dust collector or its filter, but only the resistance of our ducting and tool hoods. A good static calculator shows that this overhead resistance averages about 2.3". Looking above the 800 CFM line and to the right of about 2.3" of pressure tells us which dust collectors move ample air at ample pressure. Sadly this graph shows none of these dust collectors tested move enough air for good fine dust collection as that requires a full 1000 CFM or more airflow at this resistance level. Only the Delta, Grizzly and Jet dust collectors that this article rates as "excellent" barely moved the 800 to 900 CFM airflow required to meet the OSHA air quality guidelines and none moved the 900 to 1000 CFM required to meet the ACGIH air quality guidelines. Frankly, year of testing shows we really need one of the better quality 3 hp dust collectors if we want to get good fine dust collection with a full 1000+ CFM at our larger stationary tools.

      In addition to moving ample air, fine dust collection also requires either blowing the fine dust away outside or ample filtering. None of these portable dust collectors had the minimum 0.5-micron filters or the 0.3-micron filters recommended by medical experts. All came with under 30 square feet of filter area instead of the at least 400 square feet recommended by filter makers for fine filters. All three of the "excellent" rated dust collectors have enough pressure to power a 5" horizontal main and 4" down drops which will provide good chip collection in most small shops. None generated enough pressure to support the 7" mains and down drops needed to move the full 1000 CFM for good fine dust collection. I believe the only safe way to use any of these dust collectors is to place it and vent it outside with no air returned to our shops, while working with a strong fan blowing through our shops and wearing a properly fit dual cartridge NIOSH approved respirator mask.

    4. Cyclone Testing

      Our cyclone research found all magazine ads for small shops cyclones pictured either exact or very close copies of each other. Discussion on the woodworking forums by the makers of these cyclones and people that measured the different units advertised in the small shop and hobbyist woodworking magazines confirmed that all small shop cyclones were either exact or modified copies of the 5+ hp outdoor "chip collecting" cyclones built on plans from the New York Dept. of Labor, Division of Hygiene Engineering published in August 1962. This cyclone design has its roots in a basic agricultural cotton cyclone built with very high internal turbulence to break sand and dirt from cotton fiber. When used with woodworking these agricultural cyclones do an excellent job of "chip separation" breaking the fine dust from heavier. On average by weight woodworking dust is made up of about 85% heavier chips and sawdust plus about 15% airborne dust. Airborne dust particles are typically sized under 30-microns and they do not readily settle in normal room or outdoor air currents. The best of these cyclones only separate off about 99% of the heavier sawdust and chips into a collection bin while and blowing almost 100% of the airborne dust particles out the cyclone top outlet. So vendors who advertise 99% separation efficiency are really saying about 84% cyclone efficiency with all else dependent on how well their filters work. Instead of just blowing this fine dust into the outside air as is done by large commercial woodworking cyclones that automatically empty their dust bins, Delta built their smaller shop versions of their cyclones that all others copy to some degree without the automatic dust bins. Small Delta cyclones are still put outside to meet building and fire marshal requirements, but instead of automatic dust bins they use very open filters that freely pass the airborne dust. These big filters catch the chips and sawdust if the dust bin gets full because cyclones with a full bin blow everything right through. These and the copies sold by almost every small shop vendor were engineered to provide the roughly 350 CFM required a each larger tool for good chip collection. When put outside a shop with a 5 hp motor this design does an excellent job providing good chip collection for up to three machines operating at once. To collect from more machines at once, Delta offered a variety of larger blowers and motors that worked with this same sized cyclone. I have seen advertisements for up to 12.5 hp motors, but people have written me saying they had up 15 hp motors on their Delta units.

      The commercial dust collection firms whose customers must pass government air quality inspections have long shared their decades of experience which shows how to get good fine dust collection. With our blades, bits, cutters and sanders throwing off fine dust at over 100 miles an hour and our dust collection airflows moving half this fast, they found we must start with good hoods that control, direct and deliver these fast moving dust filled air streams for collection. Without good hoods, we are wasting our time. Additionally, they found that with older tool designs the only way to pull in the fine dust is to surround the working areas of our tools with a big low pressure area that sucks in the fine dust before normal room air currents blow it all over. It takes a lot more air to build a big enough low pressure area. Most small shop stationary tools that get good chip collection with 350 CFM need a full 1000 CFM to get good fine dust collection.

      At the low pressures that dust collection blowers provide, air is more like water and will barely compress at all so any small port, small duct, or tight bends in the ducting designs will severely limit airflow. To support a 1000 CFM airflow we need 7" diameter ducting or an oversized blower that generates extra pressure. It takes at least a 3 hp motor turning not less than 14" diameter impeller to power a dust collector amply to move this needed 1000 CFM. A 3 hp cyclone may provide good chip collection but it will not move enough air to provide good fine dust collection because it takes more power to force the air inside a cyclone to turn in a tight separation spiral, so we need at least a 4.2 hp motor turning at least a 14.5" diameter impeller to power a cyclone. Since most motors come in 3 or 5 hp size, we really need a full 5 hp motor for good fine dust collection at a single larger tool when working against the overhead in the longest ducting run in a full two-car garage sized shop. We need to step up to a 16" diameter impeller on our 5 hp motor to overcome the extra ducting to support good fine dust collection in a larger three-car garage sized shop.

      “bill’s� Sadly, most small shop cyclones are a mess. Small shop vendors the success Delta had using the same sized cyclone with many different sized blowers and wrongly assumed they could simply copy these Delta cyclones as they have done with so many other tools, make their own arbitrary changes, and then end up with great fine dust collectors. All do a bad job and most small shop vendor cyclones do a terrible job. There are no standards or controls on their products except what we as customers exercise through our purchasing decisions. Most small shop cyclones copied that same agricultural outdoor cyclone design engineered long before air quality standards. These copies are excellent chip collectors that move too little air for good fine dust collection and most do not generate the pressure to work with anything smaller than 7� diameter mains and down drops. Word of mouth and magazine reviews are just about all we have to go on to make informed dust collection decisions and most of that information was bad. Unlike most woodworking operations that are pretty obvious, just like the vendors most woodworking authorities and magazine editors failed to take the time to learn the risks or understand the technology and science behind good dust collection. This lack of knowledge on the part of woodworkers and our experts combined with a lack of standards, no oversight, and shoddy engineering by our copycat vendors to create a nightmare mess in terms of small shop dust collection. Most small shop vendors pretend their cyclones get good fine dust collection by simply adding a better fine filter. Without the tool hood upgrades and a bigger blower the fine dust does not get collected.

      Additionally, most small shop cyclones are sold for indoor use without telling us as customers that if we put them inside will not pass building inspections, fire marshal inspections, and many home owner insurance inspections because these cyclones when put inside violate building and fire marshal codes because they pose fire risks and a small chance of explosion risks.

      Worse, putting these cyclones inside also greatly increases our health risks. Instead of venting the fine dust away outside where it quickly dissipates and breaks down as soon as it gets damp, venting inside fills our shops with the unhealthiest fine invisible dust both from what we miss during collection and from what passes right through our filters. Fine material is expensive so many small shop vendors play dangerous games and sell us more open filters that trap the visible dust but freely pass the unhealthiest invisible dust. They can get away with calling their products fine filters by simply adding more and more to the filter until they get whatever level of filtering they want to claim. Just like the commercial vendors who vent their cyclones outside, our small shop vendors use the same kinds of outdoor filters that they vent inside. Outdoor filters have a totally different rating system than indoor filters. All filters season meaning they slowly build up a cake of dust in the filter matrix that does not come out with normal cleaning. This cake adds resistance and improves filtering about ten fold. Our small shop vendors are pretty unscrupulous. Just like pretending that the maximum airflow their blowers move under ideal test conditions for their advertising they also claim filtering levels based on fully seasoned filters. Unfortunately, the finest particles continue to migrate through our filters even when fully seasoned making them dust stores that contaminate our shops every time we turn on our dust collection systems. This is why ASHRAE who writes the standards for indoor filters requires all to be tested when clean and new. Our small shop vendors cite clean and new airflow levels and fully seasoned filtering levels. In real use our small shop filters will pass the finest invisible unhealthiest dust even when we are not making dust, so our particle counters consistently show most who vent their small shop cyclones inside have dangerously unhealthy airborne particle counts. With fine wood dust taking six months to years to dissipate and break down, venting inside builds up huge levels of invisible dust that airflow from our dust collection systems and tools launches again and again. Many small shop woodworkers use fairly toxic woods that create worsening allergic reactions. Dust from these unhealthy woods combined with indoor use of these down scaled outdoor cyclone designs that were "dust pumps" to hurt many people, some seriously.

      Even more frustrating, most small shop cyclone filters end up getting ruined far before they even become fully seasoned. These cyclones put 100% of the airborne dust into the filter. Woodworking makes so much dust so we have to constantly empty and clean our filters. Cleaning filters forces the razor sharp wood particles to cut up the filter matrix enough that most commercial woodworking facilities must replace their filters every three months of full time use. This assumes that we start with enough filter area as using too little filter area causes our filter to get dirty much more quickly, need much more frequent cleaning, and have much shorter lives. The filter makers recommend for normal levels of woodworking airborne dust we need at least 500 square feet of blended polyester cellulose filter or 250 square feet of all polyester filter material. All polyester filters are much thicker so need about half the surface area. The all polyester filters can be washed up to about three times and washing restores most of the ability to fine filter. At twice the initial cost but lasting four times longer, most businesses choose not to use the all polyester filters. Washing these filters takes away so much production time that most commercial shops simply choose to replace using blended filters quarterly.

      It is no secret that the reason I came up with my cyclone design and these Cyclone and Dust Collection Research web pages is because I was badly hurt by trusting the cyclone vendor that the magazines continue to rate as the "best" cyclone provider. Sadly, this cyclone vendor used a fear of fine dust advertising campaign to sell expensive cyclone and ducting systems. That advertising campaign proved so successful that other vendors either hired them to design cyclones or just plain copied the same cyclone design. That left the small shop market full of "chip collector" cyclones that did a very poor job of fine dust collection. Because this vendor added a fine filter, the result created a false sense of security that left shops looking cleaner while building up dangerously unhealthy amounts of fine dust that our dust collection systems and tools kept launching airborne. In addition to poor airflow and bad filtering, their cyclone and ducting design had other serious problems. By the time I finished my installation I was pretty angry because I found their unique ducting was identical to the same stuff I could buy locally for half the price, plus that duct leaked badly so took lots of my time and energy to properly seal. That cyclone plugged constantly in the cone when preparing rough stock using my planer and joiner. The ducting design was so poorly engineered the large vertical ducting runs plugged constantly and the horizontal ducting runs built up huge dust piles because the cyclone lacked the airflow to keep the ducting clear. Those piles posed a fire danger and when they broke loose slammed into and damaged my blower impeller, motor bearings, and filter.

      This design was never designed to provide the separation needed to work with fine filters. Its gravely undersized fine internal filter plugged every twenty minutes when using my drum sander. As discussed before adding fine filters with too much dust destroys the filters. The smaller the filter the sooner this happens. Cleaning that filter and clearing these plugs was a messy job that left me and my shop covered in the very dust I bought that system to avoid. I did as their engineer recommended and replaced that undersized internal filter with their recommended big third party fine filter bag. Even after upgrading my unit with a "neutral vane" plus the other changes on my cyclone modification web pages still left this cyclone needing at least a 200 square foot fine polyester filter and not less than a 400 square foot poly-cellulose blended cartridge filter. Commercial dust collector manufacturers actually recommend double this surface area as that will make the filters last four times as long, reduce cleaning frequency by a factor of four and cut filter resistance four fold.

      Chopping up the original design to fit these units under an 8' tall ceiling and break down into standard shipping boxes created a nightmare of additional problems that even all my suggested changes cannot cure. The smaller the cyclone the bigger the required motor, yet small shop vendors shrank the cyclone sizes and used smaller motors. Commercial cyclones sized the same as what small shop vendors sell typically come with either a 7.5, 10 or 12.5 hp motor, but these vendors sell these units with 1.5, 2 and 3 hp motors. Putting a huge blower fan on these and testing with a wide open inlet makes them look great for testing if you don't realize that the last two magazine tests burned up all kinds of motors from over stressing the motors by trying to move too much air. Our testing found only one 3 hp cyclone that actually moved enough air for good fine dust collection against the overhead found in a typical 2-car garage sized shop. It had all the changes I recommended, but still had serious filter problems and the normal problems caused by chopping up the original design. The only way to get a smaller motor to work with this design is to increase the cyclone diameter which kills separation efficiency putting even more dust into the filters. This also creates a cyclone too tall to fit under a normal ceiling unless you just hack up the cone and make it short. Many did just that leaving oddball sized cones that both plug when planning or doing other woodworking operations that make lots of larger chips and shavings and suck the fine dust right out of the dust bins into the filters. My OSHA inspector said most small shops with indoor cyclones end up testing with two to five times higher than the maximum OSHA allowed airborne dust levels and averaged over 10,000 times the airborne particle counts considered medically safe. These cyclones pushed indoor dust levels in hobbyist shops that do little woodworking far beyond the levels that made all commercial woodworkers ill and put one in eight into an early medical retirement. Frankly a lot of woodworkers got pretty angry and few hurt by this dismal technology including me.

      Regardless of my following my cyclone vendor's instructions and making their suggested upgrades, three months after installing that cyclone and vendor provided ducting with the improved fine external filter my woodworking landed me in the hospital. I nearly died and was left with a permanent loss of over half my lung function. Medical air quality testing showed my cyclone moved less than half the air required for good fine dust collection, my gravely undersized filter had self-destructed turning into an open sieve that freely passed most of the airborne dust, my ducting was so poorly designed it lacked the airflow to keep the ducting clear, my cyclone provided no better separation than the trashcan separator lid it replaced, and my vendor totally "forgot" to advise me of the need to upgrade my tool hoods so even had the cyclone worked with ample airflow there was zero chance of my shop having the good fine dust collection they advertised.

    5. Filter Testing

      Those with finer bag and cartridge filters almost all advertize 1 to 2-micron filters. Many of these claims for fine filtering come from the same few vendors that falsified their maximum airflows. Filters pass a range of dust particles that cycles from a maximum when new and clean to a minimum when the filter is fully loaded with an internal cake of dust in the filter fibers that increases filtering. For dust collection this creates a swing of roughly twenty fold between the highest and lowest filtering provided. Most small shop dust collector "fine" filtering bags and cartridges were advertised with their maximum filtering between 0.5 and 2-microns meaning their maximum varies between 10 and 40-microns. This leaves these filters passing almost all airborne dust when new and still passing almost all of the finest unhealthiest 2.5-micron dust the rest of the time, clearly not filtering suitable for breathing. Hopefully the dust collector makers will come out with better filters that will take these units down to a more healthy range.

      We found no dust collectors or cyclone systems with ample fine filter surface area ample to match industry standards. When fine filters are made too small they quickly plug creating constant cleaning problems. Cleaning destroys the filter pores soon opening them to also make even the fine filtered dust collectors into "dust pumps". The only way to use these units for fine dust collection is to put them outside with no air being returned to the shop. A 0.5-micron fine bag or cartridge filter at 800 CFM airflow and the relatively "dirty" air from a dust collector needs at least 200 square feet of area but typically come with less than 30 square feet, many with just a top bag only have 15 square feet. Using a smaller filter works for a short while but soon causes undersized filters to fail from too much dust loading and excessive cleaning. Those offering cartridge filters typically offer the poly-cellulose blended filters that require roughly double the surface area as the all poly felt, so also provide less than a quarter the needed filter area.

    6. Good Options

      Although many choose to use smaller dust collectors, small cyclones, and other options, the bottom line is you need to move enough air to capture the fine dust at the source, use good hoods, and then either blow the air away outside or provide ample filtering. Most small shop dust collectors and cyclones are challenged both in airflow and filtering to be suitable for fine dust collection. Many new cyclones compromise both on airflow and filter size. Although smaller filters work, the tradeoff becomes how often we have to replace these expensive filters.

      Today I believe small shop owners have more and better fine dust collection options, but most hobbyist vendor supplied dust collection systems still have various concerns ranging from insufficient airflow, poor separation, filter plugging, poor filtering, cyclone cone plugging, sucking the dust out of the dust bins, building up dust piles in the ducting, on and on. My experience in getting usable feedback from owners of these units left me feeling like a hyper ping pong ball. After spending a thousand or more on cyclone and ducting, woodworkers claim their purchase as the best or worst ever. In testing these units with an air gauge, barrel of certified fine dust and a scale, the results were very unimpressive. The typical hobbyist dust collector and cyclone moved about half the advertised airflow with minor to serious filtering problems. Most cyclones provide insufficient separation for use with fine filters. These dust collectors and cyclones in my opinion are only suitable for outside use with wide open bag type filters just like the units that most copy. Many found in their own use these same concerns and raised these issues with their vendors. Most said their concerns were passed off by their vendors as poor testing, bad setup, or not understanding the physics and proper testing protocols. Frankly, as a group the whole bunch of hobbyist vendor supplied dust collectors and cyclones would gravely fail to measure up if the US adopted the much more stern new European air quality standards. I doubt if more than the top few would actually keep the fine dust levels amply down enough to even pass US OSHA testing. With most dust collectors and cyclones actually increasing the airborne dust levels, I continue to only recommend the following three units for indoor use with filters. Here are summaries of comments made by the owners of these few units.

      1. Clear Vue & My Cyclones

        I was one of the many who bought and was badly burned by my magazine top rated cyclone. It plugged the filter after every few minutes of use, required taking the cone off to clean the internal filter, and every disassembly left me and my shop buried in dust. Although advertised as a 1200 CFM machine, with the vendor designed and supplied ducting its maximum airflow was well under half the advertised airflow and it measured as little as 90 CFM at the smaller down drops. As a result my ducting constantly plugged in a short vertical main run near the cyclone and the ducting built up huge piles. Frustrated I called the vendor repeatedly until the fellow who claimed to be their senior engineer finally admitted this cyclone which they sold to all small shop woodworkers who only used one tool at a time was gravely undersized and the putting the cartridge filter into the cyclone outlet, an innovation from their president was a nightmare. He told me to rip out the internal filter, replace it with a custom bag his firm was having a third party make for the many disappointed customers, and if that was still not enough I would need to buy a bigger blower or whole new cyclone. After making the filter change, that changed filter design was clearly self destructing from a hard airstream blasting the side of the fitler bag. I was seriously considering a major upgrade.

        I did not get that chance because I landed in the hospital. Allergy testing showed I had become severely allergic to various woods and medical air quality testing on my shop showed my my shop with more than double the airborne dust allowed by OSHA with airborne particle counts thousands of times higher than considered medically safe. My cyclone lacked the airflow to capture most of the fine dust. My vendor failed to tell me my stock hoods were worthless at capturing most of the fine dust. Both the vendor supplied internal cartridge filter and the third party upgrade they had me buy were open sieves that pushed most of the fine dust right through. I spent my months of recovery time gathering suggested upgrades then using the labs at the university where I taught engineering to test and refine the various suggested modifications to make that expensive cyclone viable. I was able to improve airflow by about a third and improve separation by about a third. I shared the results on my Cyclone Modification pages. Eventually I realized that basic design that all still use needed either vented outside or scrapped. With local problems preventing me from venting outside, I needed a better cyclone. The issue is wood gets much of its strength from silica better known as glass. This means fine wood dust is made up of a high amount of ground glass. If a cyclone does not separate off most of this fine dust before it gets to the filter, that filter will soon be history. As the dust accumulates plugging the filter the air pressure climbs enough to force these fine particles to cut and tear their way through the filter. Worse, cleaning just accelerates this filter breakdown, which is why commercial firms use filters with lots of area and clean with fairly gentle shaking.

        I started by going back to the basic cyclone physics then came up with a few novel innovations of my own. The cyclone I designed and shared on my web pages rapidly evolved into a very efficient separator which is what cyclones are for. The result worked incredibly well with my university and two other universities rating my cyclone design at 99.9% effective at removing particles sized 5-microns and larger. The closest competition as of the testing done in late 2006 is a cyclone with all the changes from my Cyclone Modifications pages providing 99.9% separation efficiency on particles sized 22-microns and larger. All who have built or bought one of these cyclones of my design swear by them. A few swore at me during the building process because you trade a lot of time for not too much savings. In spite of some grumbling on various Internet woodworking forums, building your own cyclone from my plans or a kit is a very cost effective alternative. If you are patient and have about 20 hours total time, this design offers the best performance available for less than the cost of a good 2 hp dust collector.

        After too many complained that building their own from my plans was too difficult I also licensed my design for commercial sale in kit form in trade for a small royalty fee to offset the growing costs of maintaining these web pages. After three attempts to let others build my design did not work out and my health precluded helping my young son to make kits, I moved on. Sadly, a few others without my blessings sell copies of my design without my permission or support, plus most of the vendors now copy portions of my design from my Cyclone Modifications pages. Please do not support these firms as they neither acknowledge my work nor pay me anything for my efforts, plus they send their customers with problems to me for help.

        In 2004 Ed Morgano and his son Matt followed the plans on my web pages to build one of my cyclones because they were getting ill from the huge amounts of dust being created by their CNC based MDF routing business that made cabinets. Ed was very pleased at how incredibly well this unit worked after everything else they had tried proved to be nothing but advertising hype. Ed is a retired machinist who specialized in working with plastics. He built another of these units in clear plastic to have a clear view of what was going on inside. He showed off that unit on a few forum pages and was immediately overwhelmed with people asking for him to build them these units. I gave Ed permission to build my design in trade for a small royalty on each unit sold. Although I own no part of this firm, do not manage it, and am not employed by them, I wish I did own a portion of this firm as they have done very well. With just the free small ad on my web pages and making sure each unit is well built and providing excellent customer service Ed and Matt quickly built this Clear Vue Cyclone firm into one of the top suppliers of small shop cyclones. They have done so well that their main competition has gone back to their old tricks putting up falsified performance comparisons on their web pages. Those claims are the same nonsense this vendor has been spouting since their fear based advertising campaign was proven to be a hoax back in the nineties.

      2. Other Cyclones

        WoodSucker is no longer be in business but its founder Larry Adcock deserves high praise for helping to change the dismal shop dust collection market. The 2000 U.S. Census shows six out of seven professional woodworkers work in small shops as do almost all hobbyists. These shops are mostly not subject to either fire marshal inspections or air quality testing. Most of the mass marketed import firms sold smaller indoor copies of commercial dust collectors and cyclones that had to be kept outside to pass fire marshal inspections. Bringing these units inside was building up huge amounts of fine airborne dust with the typical shop according to OSHA testing running two to five times more than the maximum allowable airborne dust levels. OSHA air quality testing was only required of the largest commercial woodworking facilities, so most of this market continued to use dust collectors and cyclones that only did "chip collection" meaning collecting the sawdust and chips amply to pass fire marshal inspections. With the small few person woodworking shop market collapsing due to pressure from large manufactures and off-shore competition, one of the cyclone suppliers to these small firms that only did "chip collection" developed a strong fear based marketing campaign. That campaign warned all small shop woodworkers that inhaling fine dust is very unhealthy, and they offered up their "chip collecting" cyclone with a fine cartridge filter stuffed inside the cyclone outlet as the ideal solution. The woodworking magazines gave this unit high praise, but the newly emerging Internet woodworking forums were a totally different story. Many high end woodworkers are very capable people with a wide range of skills who often have the money to buy top quality equipment. The many of these people who bought this cyclone setup with ducting to protect their health found adding the cyclone made things worse. Those with test meters began doing some testing and suddenly this top magazine rated cyclone vendor was in deep trouble. Their cyclone was a fraud. The filter did not work. Their free ducting design they gave away to entice people to buy their triple the normal priced ducting and cyclones did not work. Their supposedly airfoil impellers were simple very inefficient backward curved impellers. Their filter was a fraction as large as the filter makers said it needed to be to handle the airflows and dust loading. In short the many dozens if not hundreds who fell for that fear based advertising campaign were badly burned, upset, and telling others of their frustration. Instead of fixing their terrible products, that firm used their advertising might to attack and get those who were critical banned from the various forums. Quite a few bright people went to work trying to figure out how to fix these very expensive but dismally performing cyclones.

        Larry Adcock was one of the first to recognize that the whole approach of simply downsizing a big commercial cyclone and dragging it indoors was not viable. Larry is a pretty competent fellow who went to work doing the engineering to design a better cyclone. He started with the roughly 40% efficient blower and upgraded to a caged impeller design that is nearly twice as efficient. This let him move more air with a 2 hp motor than most could move with anything less than a 5 hp motor. He then incorporated the neutral vane to decrease performance robbing internal turbulence, and further improved separation efficiency with a helical air baffle better known as an air ramp. This ramp directs the air into a spiral and reduces internal turbulence. Larry opened a small shop and began offering his "WoodSucker" cyclones for sale. WoodSucker soon became the target that other small shop cyclone vendors tried to match. The pricing and performance for the WoodSucker sparked a whole new series of better performers. Larry developed a long backlog on orders with Internet forum posts consistently praising all but the noise and sometimes fit/finish. Larry responded to the few concerns about his units by greatly improving the fit and finish with his WoodSucker II. Owners consistently give that unit very high praise in all areas. Further, it came complete unlike most of the competition that needed filters, hangers, power cords, etc.

        My look at this unit showed it built like a tank and a solid performer for a small shop with normal ducting. In looking over the WoodSucker II design and airflow curves, this was the strongest available cyclone for its size motor. Because of its impeller efficiency it was the only 2 hp cyclone I would consider and it was a unit I recommended. I only recommended it for smaller 1-car garage sized shops because even it did not move ample air to handle larger shops. Unfortunately, the same vendor whose dismally performing cyclones inspired the WoodSucker, came back on the attack. As a major advertiser they paid for a magazine to run a just plain bad test. Instead of rating cyclones with real ducting on how well they collected and separated the heavier and fine dust, this magazine test only evaluated on total airflow. It takes a lot of work to force air into a tight separation spiral in a cyclone. As a result, most cyclones use oversized blowers to overcome this high resistance. If you can take away that resistance, then these blowers will move over double the total airflow that they will move when in real use. This upset vendor put absurdly oversized inlets on their cyclones and had their magazine testers do the testing with pipes sized the same as the inlets. With most using 6" diameter ducting, the WoodSucker used a 6" inlet. The resulting testing showed the WoodSucker to be one of the worst performers of all the units tested when in real use with standard ducting it is actually one of the best. Regardless, most do not take the time to really do their homework and tend to believe their magazines. What did not get out is a number of motors burned up from trying to push too much air in the top rated cyclones. Regardless not too long after that dismal review came out WoodSucker stopped answering its telephone and email.

      3. Felder RL Dust Collectors

        All of the cyclone problems reopen the idea of just buying a top quality dust collector. There are not many choices. Of all the dust collectors I reviewed prior to 2005 only the Felder RL-160 Series Clean Air dust collector actually moved ample air and provided the filtering to make it a good indoor fine dust collection system. I presume their newer even larger RL-200 would perform even better. Since my original review Felder changed its RL-125 dust collector pictured to the left to also move ample air for good fine dust collection. Unfortunately, the feedback I've received from those who have tried this smaller unit, say it really is too small both in airflow and chip capacity. Those with the money rave positively about their new clean air Felder RL series collectors that provide a staged fine dust filtering setup to be suitable for indoor use. Some of the Felder RL dust collectors come with a muffler as standard equipment. Although the maker claims these units have the capacity to run more than one machine at a time, the RL-125 specifications show it clearly does not and the RL-160 looks marginal to run two larger tools concurrently. The price tag on these units was very acceptable for when I owned a shop and cheap for those with respiratory problems. I asked John Renzetti who uses one of these Felder units to share a little review. Here is what he shared.



        Felder introduced the RL series dust collection system in 2002. The development came about as a result of much stricter standards for emissions in Woodworking shops in Germany. The German health authorities found a high rate of nasal cancer especially in those shops that returned the air directly to the shop. Felder submitted the machine to the German Government Health department for certification as a clean air dust extractor, and received approval from the BG test authority. The ratings put out by Felder are from these tests, which tested emissions and CFM of the machine with dirty filters, and flex hose with 90 degree bends.

        Dust and chip laden air is drawn into the intake port. Vacuum pressure pulls the heavier chips down into the bin, while the dust-laden air is pulled up through a bank of HEPA type filters. The clean air is then pulled through the fan blower and exhausted. The cost of the RL dust collectors will probably put them beyond the budget of most hobbyist shops. The RL125 is around $2000, while the RL160 is close to $2500.

    7. Less Viable Options

      Although many choose to use smaller dust collectors, small cyclones, and other options, the bottom line is you need to move enough air to capture the fine dust at the source, use good hoods, and then either exhaust the dusty air outside or provide ample filtering. The only other viable options for good fine dust collection must move the required air and provide good filters. The tradeoff becomes how often we have to replace these expensive filters.

      1. Dust Collectors

        We found no bag or cartridge type dust collectors in our testing that moved enough air and had ample filtering to provide good fine dust collection and be suitable for indoor use. You can make the larger dust collectors work for good fine dust collection it you put them outside with no air returned to your shop. Most find they need at least the Jet or Delta 1.5 hp portable dust collectors or at least 2 hp dust collectors from other makers to move ample air against the minimal ducting in a small shop. I recommend converting these units that do not come with fine filters to at least a large fine filter bag or preferably a large cartridge filter to get more airflow. Although it is easy enough to make your own cartridge conversion, you can buy retro-fit parts from some vendors or buy a conversion kit from Wynn Environmental that will work on a range of dust collectors that have an 18" to 20" diameter bag tree. I personally modified a Jet dust collector with a Wynn filter because Jet has long had one of the better performing and nicest built hobbyist dust collectors available. Fit and finish have always been excellent, and unlike many who use import motors, Jet has gone that extra mile to provide a top quality motor with all the right qualities to provide years of excellent service including good bearings, heavy duty insulation, and thermal protection. To me buying a cheap dust collector makes little sense because this will be the most heavily used motor in our shops. Unlike far too many, Jet also provides real airflow CFM and filtering numbers that prove accurate under independent testing. Regardless, most find putting the dust collector outside creates emptying problems, plus keeping the filter clean proves too much work, so most eventually shift over to using a cyclone dust collector.

      2. Trashcan Separators

        The simplest two stage dust collection system uses a trashcan separator lid and these work well for "chip collection" but poorly for fine dust collection. They can keep wood from beating up your filters and protect your dust collector impeller. I had many years of excellent service from my simple Woodstock (made by Grizzly and sold by many) plastic garbage can lid separator, but did have to seal the hoses and add insulation foam to seal the lid to the trashcan. Sadly, my separator totally failed to work when I upgraded my dust collector and began using larger hoses. With the 4" hoses going to it, it worked fine. When I went to 6" hoses going to 4" just as they entered that unit, it simply emptied my 40-gallon trashcan of all but large blocks. Most others who upgraded their hoses from 4" to 6" and had a 1.5 hp or larger blower found their trashcan separators equally useless. That bigger duct allows so much air to be moved that it simply sucks all out of the trashcan but the heavy blocks. If you read over the theory on drop boxes and swirl tubes, you will find you only need a 5' 1" diameter trash can that stands about 7' tall to work with an 800 CFM airflow. I've done a lot of experimenting with cyclonic separation tops and they work better, but tend to cause even more resistance than a cyclone. Many of us are still working on a viable solution that will work with a high airflow and still be as easy to use and empty as the trashcan.

      3. Small Shop Cyclones

        Most small shop cyclones are designs taken from outdoor commercial cyclones that barely move ample air for good "chip collection", so remain a poor choice to bring indoors with fine filters. The worst cyclones are add-on units that attach to existing dust collection blowers. These add-on cyclones add so much overhead they kill the airflow needed for "chip collection" saying nothing of having no where near the airflow needed for good fine dust collection. The basic cyclone design and engineering for almost all small shop cyclones requires a 2 hp motor for "chip collection" and a 5 hp motor for good fine dust collection. Use of a "neutral vane" and the other changes suggested on my Cyclone Modification web pages can increase efficiency considerably, but not enough for most vendors. Our testing only found one 3 hp cyclone that would actually move the 800 CFM needed in a small shop with minimum overhead resistance. If you toss the indoor fine filters and replace them with big free flow filters with the air directed outside, these make excellent find dust collectors. Otherwise, they just do not provide ample separation, airflow, and filtering for indoor use.

      4. Home-Built Cyclones

        There are a number of cyclone plans being sold that are all copies of the same basic "chip collection" cyclone designs. Although recommended for use with fine filters, they units quickly destroy fine filters so at best provide a false sense of security. They also mostly call for tiny blowers that only move enough air for "chip collection". With the changes on my Cyclone Modification pages and a big enough blower these do make good fine dust collection cyclones again if you direct the air outside instead of trying to filter it amply for returning indoors.

  5. Frequently Asked Questions (FAQs)
    1. Bill, I much appreciate the considerable work you have done to help woodworkers better protect their health, but you have given me far too much. I don't have the time or patience to read through and understand all this. I have just converted over my two-car garage to a shop and just want four simple dust collection questions answered. - Lou

      1. First, many of my family members and friends have all done woodworking for ever and nobody has ever gotten sick. Just how serious is this fine dust problem and is it worth investing the money to provide extra protection for my family and me?

        I truly hate answering this question over and over again. Not only have I gone to considerable pain to cover it in more depth than most ever want to hear on my Medical Risks web pages, this question forces me to try and be objective when I really want to just kick some sense into woodworkers who don't realize they are putting themselves and those close at serious risk. Please re-read the Risk section above.

      2. What are the minimum requirements I should look for in deciding on what dust collection I need? Air engineers did considerable testing and shared what they have learned about fine dust collection since the 1950s as to what it takes to address the fine airborne dust problems. They found we must do the following.

        1. First, fix our tool ports and hoods so they do not spray the dust away before it can be collected. Many blades, bits, cutters and even sanders launch fine dust at over 100 miles an hour, but our dust collection airflows only move at about half this speed. Without good hoods to contain, control and deliver the fine dust for collection there is zero chance of getting good fine dust collection. AAF, one of the better known suppliers of commercial dust collection equipment to facilities that must stay in compliance or can be shut down was kind enough to let me share their many sample tool hood upgrades on my ducting web pages. Those same pages also share various ways to upgrade from the smaller 4" collection ports provided on most machines using better quality laser welded Lindab or Nordfab flanges, or less expensive readily available HVAC flanges.

        2. We then must provide ample airflow at each machine for good fine dust collection. Air engineers also established minimum air flow requirements tables for each size and type of tool from careful testing and experience. Since our larger small shop tools are identical to smaller commercial tools we can use this same information. Most of the large commercial tables and all are near exact duplicates of each other. Each of these CFM requirements tables to meet OSHA standards show we must move about 800 CFM at our larger tools and dustier operations. That 800 CFM is not the advertising hype maximum airflow that is about double what a blower actually provides in real use. That 800 CFM is instead what we need to move after taking away the overhead resistance in your shop from your tools, ports, hoods, ducting, separator, filters, etc. Going through the same calculations and testing shows we need 1000 CFM to meet the higher recommended medical air quality standards already adopted in Europe.

        3. We must upgrade our ducting to ensure moving ample air. Air engineers long ago established we should target our ducting systems to move air at 4000 FPM velocity to keep the ducts clear without putting on too big of a blower. We can use this 4000 FPM and the 800 CFM airflow requirement in the simple air formula AREA = CFM/FPM to calculate our ideal duct size. A little math shows we need almost exactly 6" ducting to move this much air at the right speed. Ducting size is very important because air at the pressures generated from our small blowers is more like water as it will barely compress at all. Use of the typical 4" and smaller ports or ducting that come with our tools and is available from most woodworking ships is similar to using a water hose that is too small or having a valve partially closed. Any obstruction will serious degrade our airflow. For instance a good 1 hp dust collector blower that can deliver a maximum 800 CFM through a 6" test pipe ends up only delivering about 550 CFM when pulling through a 5" diameter pipe, 350 CFM through a 4", 200 CFM through a 3" and 90 CFM through a 2" pipe. If we want to move the needed 800 CFM to our larger tools to meet OSHA standards, we then either need blowers that can generate much more pressure or to use all at least 6" diameter pipe from our blowers to our tools. To meet the 1000 CFM needed to meet the higher air quality standards we should use all 7" diameter ducting. If we have a tool that requires two collection points, then we need to make sure that the area of each leg after we split our pipe added together stays very close to the same as our main ducts. A 6" pipe has roughly 28.25 square inches and a 7" pipe has an area of roughly 38.48". My ducting pages go into far more detail.

          Also discussed on those same ducting pages is the importance of ducting design. Sharp angles, rough ducting, obstructions, rough flex hose, bad transitions, tight curves, etc., all seriously reduce airflow. We can use a Static Calculator to determine the total overhead of our ducting and other dust collection components. It only takes a few minutes playing with a static calculator to realize almost all magazine articles and vendor advice on laying out our ducting is dead wrong. Most of this advice was foolishly assumed to be transportable from commercial shops. Ducting does not work that way in small shops because we use tiny blowers that do not generate anywhere near the same pressures or air volumes. Our blowers are sized to barely overcome the resistance of the longest ducting run in our shop coupled to the tool that needs the highest airflow and just collect from one tool running at a time. Using a downscaled version of a commercial ducting design ends up expecting to use a big enough blower to collect from all machines working at the same time. As a result the amount of air moved in a commercial design creates a tree like structure where right next to the blower we need a huge main to carry the airflow going to all the branches. With just one run working at once we instead need to maintain a very close to constant sized duct from the blower right to the machine or we end up with the airflow in the larger mains slowing too much. If that airflow slows too much, the mains build up dangerous ducting dust piles in the larger main pipes. Dust piles can cause ducting fires. When these piles break loose they can ruin our motor bearings, impellers and filters. Moreover, when they break loose they can create a potentially explosive dust to air mixtures. In small shops with a single point of collection we need to use nearly the same sized ducting throughout. Most end up needing at least 6" diameter mains and down drops whose area added together ends up matching the roughly 28.25 square inches of our 6" mains.

        4. Air engineers then tell us to either send the air outside or filter it. They always recommend sending the air outside and using radiant heaters to keep from having bad heat losses. They found that keeping the air inside and trying to filter it is a nightmare. First, filters need to comply with some standard and that standard ranges from wide open just blowing all the fine dust right through to filtering at 0.1-micron or better. Current cyclone makers would like us to believe that filtering to somewhere around 10-microns is ample. As discussed before, the medical experts would like us to provide at least 0.1-micron filtering as is now the European standard. I found it difficult and expensive to get 0.5-micron filters. Moreover, as the fineness of our filters increases, we have to either provide much better pre-separation or significantly more filter area.

      3. I fully expect to follow the footsteps of my father and grandfather starting my woodworking hobby modestly with a good set of hand tools then as I get more proficient adding a few stationary tools in the basement, and eventually building a dedicated shop. I suspect most go through a similar progression. How should I manage the fine dust during the growth of my hobby? For new woodworkers I recommend starting woodworking as a fair weather activity where we work outside wearing a good certified NIOSH dual removable cartridge mask when making fine dust. I use a 3M half mask in my size from a local hardware store that stocks a range of filters allowing me to also use this mask when painting and spraying my garden. This lets us get going without a huge cost in tools or putting our health at risk. The basic tools will be useful around the home even if woodworking turns out to not be a long term hobby. I now personally do quite a bit of my work outside using a good hand held power saw, router, jig saw, drill, orbital sander, and oscillating spindle sander with a guide system instead of my large stationary power tools. I find I can do all just as well, with far less setup, and considerably more ease especially when working with large sheet goods. Festool probably makes the nicest of these type systems and other vendors offer a range of similar offerings. I personally use the Eureka Zone EZ-Smart guide system and table. This system is so versatile my daughter and I made her a nice desk in the fall of 2005 without doing any machining or sanding indoors.

        Most work indoors and end up getting at least two dust collectors before upgrading to a cyclone system. If you have a garage attached to your home or worse, a basement workshop like yours, then I strongly recommend skipping this step and going straight to a good cyclone based system. I also recommend use of radiant heaters in your shop and blowing the dust away outside ensuring that you provide ample make up air to keep from drawing deadly carbon monoxide backward through your vents, stoves, and fired appliances.

      4. And finally, like most I am supporting a family, so have serious financial constraints on my woodworking expenditures. I also want to end up with good quality equipment that will last. How do I manage this dust safely without breaking the bank and will you recommend specific brands and models for each phase of this adventure? If you will not work outside, I still suggest you buy or make a cyclone that you vent outside. The cost to build your own is about the same as a typical dust collector ample for your sized shop, and will save you having to go through the two or more dust collectors that most of us have to buy before waking up. I personally kept my Jet 1.5 hp dust collector because it is a well built unit and with my DC Cartridge Conversion works great for quick jobs where I don't want to turn on the cyclone. At the same time, I know this unit pumps too much dust into the filter that I need to change that filter frequently to keep myself protected.

    2. Bill, I have a small 2-car garage sized shop with no ducting, what dust collector should I buy? I don't recommend buying any dust collector, but if you have to please ensure it moves enough air for good fine dust collection, that you use ducting to put that unit outside where the fine dust cannot blow back indoors, and that you use fine open filters that flow the most air to provide the best collection. Also, be aware that many vendors either lie or advertise exaggerated airflows. The best two 1.5 hp dust collectors are made by Jet and Delta, yet neither of these generates ample pressure to overcome the normal resistance to power the ducting in your two-car garage sized shop plus the resistance of your dust collector filter. Your shop needs one of the better quality 2 hp or larger dust collectors to provide ample airflow. One caution here, please don't get sucked in by false advertising that offers 2 hp and larger dust collectors that plug into a standard 120V plug. Some vendors play games rating their motors based on starting amperage instead of working amperage so call 1.5 hp and smaller motors 2 hp to as much as 6.75 hp.

    3. Bill, you have me confused again. You say we need 800 CFM in one place as a minimum yet in other places recommend at least 1000 CFM at our larger tools and dustier woodworking operations. How much CFM do you recommend? Air engineers have spent over fifteen years refining their tables that show the minimum airflow needed to provide the collection at different tools ample to meet OSHA air quality requirements. Since most large hobbyist tools are identical to smaller commercial tools, we can use these same tables. CFM requirements tables for our tools to meet the medical air quality requirements already in use in Europe are not yet available, but the testing shows we either need tools built from the ground up to totally contain the dust as it is made or that we need about 1000 CFM at most larger hobbyist tools and dustier operations. In general, if you add about 25% to the existing CFM requirements tables you will get fairly good CFM numbers to meet the higher standards.

    4. What cyclone do you recommend? In six years of testing I never saw a single small shop cyclone other than the WoodSucker II and the Clear Vue Cyclone using my design that provides good enough separation to be used indoors with filters. Although there is again considerable advertising hype where vendors test their cyclones against heavy chips and make outrageous separation claims, all other small shop cyclones are downscaled copies of the early outdoor commercial "chip collecting" cyclones. These 5 to 12.5 hp cyclones were engineered long before the current fine dust standards went into place. They do an excellent job of "chip collection" and use wide open filters engineered to pass all the fine dust into the outside air where it just blows away. This means they blow the 30-micron and smaller particles that make up almost all of airborne dust right through. With these units placed outdoors to meet fire and building safety codes, their only real problem is being built to only move the 350 to 450 CFM needed for good "chip collection". To make one move that airflow for good fine dust collection they typically need just about twice the blower size. Instead, small shop vendors sell them with blowers smaller than half the original size where a 5 hp cyclone was only considered ample to collect from one or two machines at once. Worse, ignoring commercial fire and building codes to bring these indoors with either too open or undersized filters creates a nightmare of dangerously unhealthy fine dust exposures where many will follow my lead and eventually get ill because these units are dust pumps. In short, either build your cyclone from my plans, buy one from Clear Vue Cyclones, or buy one of the larger at least 3 hp cyclones and toss the filters and direct the air outside.

    5. You confused me with your blower fan tables. On one hand you recommend use of a 5 hp motor to power your cyclone, but the fan table says I need 7.5 hp and you say elsewhere that I can get by in my average sized shop with a 3 hp cyclone. How much motor do I really need for my cyclone? How about I answer this question with a question, how big enough of a motor is needed to power my car? The answer is the same it depends upon the size of car and its use. A typical chip collection cyclone that is a copy of the original Delta outdoor cyclones that most vendors copy needs roughly a 5 hp motor. Even with all the changes suggested on my Cyclone Modifications web page that many vendors have copied often without giving credit for this work, the best resulting cyclone still shoves more than half the overall airborne dust into the filters. This quickly kills filters making these units in my opinion inappropriate for indoor use with filters, so I only recommend their use if you blow the air directly outside with no filter. Dropping the overhead resistance of your filter makes these units able to support collection from one large machine in a typical two car garage average sized shop with just barely a 3 hp motor. Unfortunately, because many small shop blowers are so sloppily built, they generate considerably less than commercial blower air flows, so many 3 hp small shop blowers will be undersized. More, cyclone vendors oversize impellers to compensate for the high resistance of our cyclones and ducting. Otherwise the impeller would just turn doing minimum work because it becomes air starved and cannot get the air it needs. Using a bigger impeller generates more pressure and lets us move more air. We carefully balance motor size, impeller size and resistance to provide maximum airflow without working our motors beyond their rated amperage. What may be a perfect balance for your longest ducting run and biggest tool can be a disaster for your motor when collecting from a close machine with minimal resistance. The motor can try to push more air than it has rated amps to move. This soon burns up motors. That is why I recommend use of a 5 hp motor on my cyclone design that works great with a high resistance long run. It really needs only a 4 hp motor to ensure motors don't burn out, but because motors come in 3 and 5 hp, not 4 hp, I bumped up the impeller size from 14" to 15" in diameter to use that extra horsepower without putting the motors at risk. The result is higher pressure and the increased airflow to ensure meeting the airflows needed for collecting the fine dust at the finer standards now being adopted.

    6. Perhaps the most popular dust collector available today is the very inexpensive Harbor Freight 2 hp dust collector. Can I use one of these sitting outside my shop for good fine dust collection? Can I later use this same motor and blower to power a cyclone? When that dust collector first came out I tested it thoroughly, did a long write-up on it that was shared out on a number of Internet sites, and then upgraded those write ups a number of times as this unit evolved. It started as a piece of junk with innumerable initial failures, but Harbor Freight made good on the units that failed and fixed the many problems. That still leaves this as a real roughly 1.6 hp dust collector that moves about the same airflow as many of the 1.5 hp units. I found it marginally lacking in total airflow for good fine dust collection as a dust collector and severely lacking in power to meet the much higher demands of a cyclone. Doing a fine filter upgrade as recommended on my DC Cartridge Conversion page raises the airflow amply for it to be a good unit to use outside a small to medium sized shop.

    7. Bill, you have me really confused and seeing things. I read over both the American Woodworker and Wood Magazine Cyclone & DC Testing and just about every cyclone they tested goes well over the 800 CFM that you require. They also generate far more pressure with a 2 hp motor than you say is needed for a 2-car garage sized shop with ducting. They clearly label the ducting overhead on one of the charts. Do you agree they move enough airflow, and if not why not? This is one of those questions that does not make my day. No, those reviews use test conditions that significantly differ from real use. Specifically they test with oversized test pipe, almost no ducting, no attached tool or tool hoods, and no filters. Adding that overhead back in and you will find there is no 3 hp or smaller cyclone that will give you the airflow to do anything more than just give you good "chip collection". You really need a full 5 hp cyclone to get good fine dust collection. Here is why. If you look at a good fan table it will tell you how many horsepower it takes to move a given airflow at a given level of resistance. A typical two-car garage sized shop has an average tool resistance of 2.3", at least 3.5" resistance for the cyclone, 0.5" more for big fine filter, then another at least 1.6" resistance for the ducting for a total of at least 8". Only the top two brands actually tested with blowers that move as much air as normal commercial blowers of the same size. The commercial blower tables show that at 8" of average resistance to move a real 800 CFM you need to use a 14" diameter blower impeller turned by at least a 3 hp 3450 RPM motor with our using ducting sized at least 6" in diameter. We have decades of shared experience from those major firms who guarantee customer air quality. They and medical experts recommend moving a full 1000 CFM not just 800 for good fine dust collection. The fan tables show moving this real 1000 CFM against 8" of resistance requires a bigger14.5" diameter impeller turned by an over 4 hp 3450 RPM motor plus we must use at least all 7" diameter duct. To be able to use the much less expensive and easier to find 6" diameter duct, I compensate in my designs by using a 15" diameter impeller turned by a 5 hp motor. There is enough additional capacity in this motor that I now personally use and recommend use of a 16" diameter impeller.

      We adjust for pressure by using bigger impellers and bigger motors because our direct drive motors are fixed speed. Many small shop vendors now advertise their cyclones with 14" impellers, a 7" inlet, and only 2 or 3 hp motors. Looking at the same fan table says a 14" impeller can move a whopping 1377 CFM airflow at 8" but to do so it is drawing a real 3.77 hp. Neither a 2 nor a 3 hp motor will stand that kind of load for long. If as before we look at the minimum load from collecting from a big tool right next to the cyclone with minimal or no ducting this same sized impeller draws an even bigger 1649 CFM at 4.58 hp. That load will soon burn up either a 2 or 3 hp motor, but until it happens oh do these look good. So then the next question is how to they make them work with 2 and 3 hp motors and not burn out the motors all the time. The answer is the same. These blowers are far less efficient than commercial blowers so the design problems, poor manufacturing, and use with restrictive ducting saves lots of motors. It also makes for some pretty dismally poor test results. We do not get more airflow for nothing.

    8. What makes your cyclone design a better choice than the many other offerings? Four things cost, airflow, separation efficiency, and overall resistance. You can build one from my plans and pay me little to nothing, or buy one from Clear Vue Cyclones with a 5 hp top quality motor for less than most other vendors charge for their 3 hp units with lesser quality import motors. Most small shop cyclones are built to provide the typical "chip collection" airflows of about 350 CFM. The bigger 5 hp cyclones provide a real airflow of about 800 CFM needed at our larger tools to provide fine dust collection ample to meet OSHA air quality standards. My cyclone design is engineered to provide a real 1000 CFM at our larger tools to provide the airflow needed to meet the medical recommended air quality standards that are 50 times more strict than OSHA and already the European standard. The cyclone separation has a real separation efficiency instead of some fabricated efficiency made up in the back advertising rooms. In hard numbers my cyclone on standard test dust that matches the OSHA standard of 30% fine airborne dust my cyclone design provides an overall separation efficiency of over 99.7% separation efficiency by weight. This gives a real fine dust separation efficiency of about 98% versus a typical neutral vane equipped cyclone at less than 44%. Since this fine dust plugs and destroys expensive filters, this separation efficiency saves both our health and pocketbooks. I have people who make two to three hundred pounds of fine MDF dust a day using my cyclone for six months or more before they need to clean their filters. My prior "best" cyclone allowed less than twenty minutes of routing MDF before I had to stop and clean the filters. Finally, my cyclone design has far less resistance than most other units so the horsepower of your blower motor goes into separation efficiency instead of getting wasted overcoming cyclone overhead. The combination lets you provide good fine dust collection airflow and separation before filtering that are far beyond OSHA, ACGIH, and approaching medically recommended standards today instead of struggling with equipment that mostly will not meet the OSHA standards that most have already abandoned because these air quality levels leave too many getting ill.

    9. What do you have to say about the current top magazine rated cyclones and best selling cyclones? Do you recommend any of these? I think the original Delta 5 hp chip collection cyclone that most small shop vendors copy to one degree or another is probably the top selling unit and if you count all the clones it has been the top selling for many years. I think this is a great cyclone if you put a big enough blower on it and direct the air outside exactly as the cyclone was designed. I am not at all in favor of any of the copies with tiny motors, blowers, and filters. They lack the airflow, separation needed to protect the filters, and ample filter fineness and sizing to make good fine dust collectors.

      In terms of magazine ratings I have spent countless hours helping to educate magazine authors and editors to improve their testing protocol for cyclones and dust collectors. Future tests should look at the important things like separation efficiency, resistance, airflow at typical shop resistance levels, and provided filtering. Hopefully these many long discussions have weaned them away from this fallacy that "best" is the one that moves the most airflow claiming the highest CFM. I can change test pipes and make just about any unit I want appear to be a "maximum airflow" winner. Far more important is will each unit provide the airflow needed for "chip collection" or good fine dust collection with the size ducting at the resistance levels typical for each sized shop. Best is the unit that best protects our health with enough airflow to collect the fine dust as it is made, enough power and air pressure to overcome the resistance of our normal ducting, and then the ability to safely get rid of that dust.

      When I go looking for a vendor I want one I can trust. I don't trust any of the top rated cyclone makers because there has been too many years of funny business with bogus health claims, exaggerated airflows, falsified separation efficiencies, and dangerous filtering claims. I do know a few of the better known vendors continue to be in a very open and ugly public fight on their web pages and Internet woodworking forums leaving me feeling their bottom line is different than my interest in helping to protect the health of woodworkers. I have had so many pieces of hate email against all of these small shop cyclone makers except Jet and Delta that I hope to never receive another. These concerns sadden me but are not much of a surprise. In spite of my prior negative experiences I still chose to do my best to help all improve their cyclones. Many have lifted my advice then claimed it as their own. Frankly, I have no need, want or desire to comment further. The only public recommendation I will make is their 3 hp cyclones work pretty well for average sized shops if you toss the filters and exhaust the air directly outside. I would not consider any of them appropriate to use with indoor filters.

Copyright 2000-2013, by William F. Pentz. All rights reserved.