Cyclone and Dust Collection Research


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Air Quality Testing

  1. Introduction

    We do airborne dust measurement to know when to protect ourselves from the two main risks. The first and most immediate problem is airborne dust contains many very unhealthy chemicals. The chemicals found in wood dust have many toxic health effects ranging from being poisonous, strong irritants, sensitizers that create allergic reactions, carcinogens that increase or risk of cancer, and some chemicals that create a few serious woodworking related diseases. And, second airborne dust also contains fine invisible particles sized under 10-microns that cause both immediate and permanent long term respiratory damage. These fine particles get right by our normal respiratory protections and depending upon their size get stuck or lodged at different places in our respiratory system. These stuck sharp particles not only release the chemicals they contain and carry, they also cause some damage. The medical research is clear every exposure to these fine invisible particles causes some measurable loss of respiratory capacity, some of this damage becomes permanent, and the higher and longer the exposure the worse the damage. Fortunately, we are born with far more capacity than we need for day to day activities, so most need a decade or more before the damage builds up enough to start affecting the quality of our lives. A good particle counter will give us an idea of how much dust we are breathing. We clearly want to avoid taking in an excess of chemicals and too many fine particles. You can learn more about these airborne dust risks on my Medical Risks web pages.

    Newer computer and laser based technology steadily lowered the cost for test meters. This created a number of new and much more affordable meters. The much wider availability and use of these less expensive and far more accurate particle counters convinced the European Union to change their testing standards to permit use of these new meters.

    Even with these significant technology improvements and cost reductions the cost, accuracy, size, time, and knowledge to do air quality testing remained prohibitively expensive for small shop owners. That has recently changed, and now woodworkers all over the world are starting to do their own testing. This testing is exposing much of the small shop dust collection market as something that at best works poorly and in most causes actually makes our indoor air quality far worse than if we just worked with an open doorway and strong fan blowing the dusty air outside.

  2. Caution

    Unfortunately, knowing how much dust we take in misses one very important part of dust exposure. Knowing how much dust we are breathing does not tell us how dangerous this dust actually is. In addition to the fine particles causing damage, dust also contains many different chemicals. For wood dust we know trees produce many different strong chemicals to protect themselves from insects and other predators. Wood is also exposed to many other chemicals from the molds, fungi, yeasts, lichen, mosses, etc. that break wood and bark down, plus other chemicals such as insecticides, herbicides, preservatives glues, solvents, finishes, drying agents, fine metal filings, etc. As discussed in my Heath Risk pages even a good Wood Toxicity Table is still not going to warn us about these other chemicals commonly found in wood and other airborne dusts. When working with dangerous, unknown, treated, or moldy woods we should always wear a good NIOSH dual cartridge respirator and keep wearing our respirator until we thoroughly clean our shops.

    The other serious problem with wood dust is taking in too much dust in a short period. Too much dust can clog our airways, sinuses, throats, and lead to chronic infections, pneumonia and a variety of respiratory diseases. This is why OSHA sets a maximum personal exposure limit of 15 milligrams of dust per cubic meter of air (mg/cm3) over any fifteen minute period.

  3. Airborne Dust Measurement

    Traditionally dust collection for woodshops was always monitored using different blower based devices that collected the particles on a filter. The filter was weighed before testing then after a typical eight to nine hour work day. The dust weight divided by the number of hours the test ran gave an hourly average weight or mass of the airborne dust.

    The newer particle counters use a focused laser aimed at a photocell grid similar to those used in cameras with a computer that can track, size and count the various particles. Based on particle sizing, these units can also calculate very accurate mass readings. The result is these meters can provide near real time sampling giving both particle counts and airborne dust levels by weight. The European Union has already changed their standards to permit use of these new laser based particle counters rather than having to go through the full day testing ordeals. The U.S. Environmental Protection Agency (EPA) has similarly updated to permit use of particle counters, but also provides weight based standards.

  4. Airborne Dust Standards

    The numbers of airborne particles are so huge and difficult to measure, that almost all have traditionally measured airborne dust by weight. This is why most air quality standards and recommendations revolve around weight based measures. The Department of Labor, Occupational Safety and Health Administration (OSHA) recommendation is no more than 5 milligrams per cubic meter (mg/m3) average over a full work day with no more than a 15 mg/m3 exposure during any fifteen minute period. The American Council of Governmental Industrial Hygienists (ACGIH) is a not for profit organization of governmental hygienists that recommends a five time tougher standard of 1 mg/m3. The medical research and medical recommendations recommend 0.1 mg/m3 which is fifty times tougher than the OSHA standard. The medical recommendations have now been adopted in Europe and by the EPA. These differences are partially due to the OSHA and ACGIH standards applying to all airborne dust while the EPA standard only applies to the under 10-micron fine dust.

  5. Particle Counters

    The newer test meters such as my MetOne Aerocet meter actually counts the particles of different sizes and uses these counts to give a fairly accurate measure of the weight of airborne dust.

  6. Politics

    It is no secret that the large woodworking facility owner associations have fought fiercely since the 1950s all attempts to either classify wood dust as dangerous or impose any major standards. Conversely, the woodworker unions with some help from medical researchers have long fought to impose strong standards of protections. For the last fifty years this battle has been very one sided. A few minutes on the Internet doing searches will show numerous articles written by well known universities and research organizations that clearly state woodworking makes no fine dust, the fine dust particles made by woodworking are not dangerous, and there are no short or long term health risks associated with intake off too much airborne wood dust.

    The reality is taking in too much even totally harmless dust causes us serious short and long term health problems. We start by getting badly plugged up. Too frequently getting all plugged up causes us to develop sore throats and other irritation which if continued leads to sinus, throat, and respiratory infections. Chronic infections often cost us our sense of smell. Too much exposure can also lead to eye and skin problems. Meanwhile the fine particles end up costing us our respiratory capacity. Those who work in traditional large woodworking facilities that vent outside lose about 1% of their respiratory capacity per year of work. This is exposure dependent and small shop workers that vent their dust collectors and cyclones inside consistently get many hundreds of times higher exposures. So, there is definitely an upper limit as to how much dust we can take in. Instead of being owner paid for reports, the peer reviewed medical school articles must pass a rigid review by skilled physicians to make sure the information, testing, approach, and conclusions are valid. The peer reviewed medical research shows that wood dust carries a wide range of unhealthy chemicals, plus the fine wood dust particles which look much like asbestos fibers under an electron microscope are very unhealthy.

    The cost to appropriately clean the air to medical recommendations is not that high, but woodworker owner associations continue to strongly oppose all efforts to get wood dust certified as dangerous. My personal opinion is these large facility owners are running scared, particularly with most already voluntarily maintaining their facility air quality to more than five times better than OSHA recommended. The conclusive proof of the dangers of asbestos wiped out the asbestos industry literally overnight, almost entirely from huge class action law suits. Although asbestos was used in many things, its popularity was nothing like wood. The 2000 U.S. census showed the wood working industry including the timber industry, paper industry, and wood product manufacturing industry was the fourth largest employer in the U.S. Add in home construction and this becomes the largest employer in the U.S. Suddenly raising the specter that wood dust causes a range of serious long term health problems that do not affect most until our later years could unleash economic chaos across this country. Between the fear of what widespread knowledge of this problem could do and strong financial support pressure our government and courts have continued to avoid imposing mandatory worker protections.

  7. Credibility

    Until very recently very few woodworkers were willing to believe that woodworking creates much if any of the finest invisible 10-micron and smaller particles known to be so harmful. The problem is the small shop vendors that make our tools and dust collection equipment continue to say the same things the large woodworking facility owner group produced information says. All including some of the best known for their dust collection efforts continue to say woodworking creates little to none of these fine invisible dust particles, the particles that are made are not dangerous, and there are no short or long term other risks.

    Having helped build air quality meters and test equipment I had no problems at all with the idea that our air is filled with untold numbers of fine particles. The logic and arguments in the current woodworking literature convinced me that we make almost no small fine wood particles. At the same time I was trained as a biomedical engineer, flew jets for ten years, and worked with enough hazardous material that I developed a healthy respect for taking care to protect myself. From this perspective I upgraded to the best available small shop hanging air cleaner, the "best" rated small shop dust collection system using the "top" rated cyclone separator with vendor designed and supplied ducting, plus an upgraded fine filter. Also knowing that some woods are pretty toxic, I also consistently wore a good NIOSH approved 3M custom fit dual removable cartridge respirator mask whenever making fine dust. Having grown up in woodworking, I knew many who would laugh at my efforts. Few if any ever cared much other than wearing a mask when making lots of dust. I also know quite a few old salt woodworkers who have chain smoked cigarettes and done woodworking full time with some of the most toxic woods since before there was grass on the hills. They were still going strong into their eighties and longer.

    My suddenly facing having to give up a lifetime of woodworking and three generations of tools, when I was the one who took that extra care to protect myself struck me as totally unfair. I paid quite a bit to get a medical air quality test run on my own shop and home back in early 2000. That test really upset me because it showed the cyclone dust collection system I bought to protect myself is what actually caused my problems. This system created a terribly bad false sense of security by filtering off the heavier dust leaving a clean looking shop while it pumped the fine invisible unhealthiest dust right through into my shop. We created 151,000 times more fine dust than it takes for an average two-car garage to fail an EPA air quality every time we make another twenty pounds of sawdust. My clean looking shop rapidly built ridiculously high amounts of fine dust. After three months of no woodworking and parking our cars in my garage based shop at night there was still so much fine invisible dust in that clean looking shop that my inspector required us to put on our respirator masks because just our walking around stirred up dangerously high amounts of dust without doing any woodworking at all. My home also was badly contaminated with dangerously high amounts of 10-micron and smaller invisible fine dust particles that went right through my fine home HVAC filters and air cleaners. When I shared the results of these tests with fellow woodworkers on these pages some listened, some agreed, and many did neither. In fact, it kind of became a game to see how far others could insult me and my web page efforts on some of the less well behaved Internet woodworking forums.

    I tired of that nonsense so spent the considerable money to buy my own high quality calibrated mass/particle counter. I did testing all over the State of California, and instead of being able to release the clear information that not one single small shop cyclone or dust collector passed any of the air quality tests except my design, I found myself caught between a rock and hard place. The vendor whose equipment landed me in the hospital threatened to sue if I released the information that their firm was still making cyclones and filters that actually made the fine dust problems worse. Having already weathered six prior threatened suits, I tired of spending my little money on attorney bills. My attorney had me remove every reference to this still top magazine rated vendor from my web pages and not publish the detail test results from all my testing. Those test results were doubly ugly because they caught this same vendor flagrantly misstating both the airflow and filtering, plus showed their current ducting designs are little better than the mess they created for me back in 1999.

    Wanting a way for individual woodworkers to do like we did with air volume testing back in the early 2000s I decided two years ago to work with Clear Vue Cyclones to get a custom but affordable air quality meter built. If hundreds of people all over are showing that their shops have dangerously unhealthy particle counts and that their expensive so called fine filters were serving as dust stores that surged out huge amounts of fine dust every time we turned on our dust collectors and cyclones, suddenly I would no longer be a lone voice ignored by all except the few with the appropriate scientific background. Our efforts to get a new meter just did not work out.

    Much to my surprise, in late 2007 the Dylos Products Corporation began selling an inexpensive laser particle counter which does exactly what I wanted to see. This inexpensive meter provides small shop woodworkers to have access to a very accurate meter. I bought one and have been testing it. It gives near identical results as does twenty times more expensive MetOne Aerocet 531 meter. The Dylos meter is a good solid air quality test meter at an affordable price. Like all focused laser based test meters particle counts get inaccurate when measuring dangerously high dust volumes because larger particles shadow the smaller. This meter still does an excellent job of clearly showing when dust levels become a serious problem. I think it is a great product and worked with this firm to setup a few mass buys with a discounted price for those who want a meter to track the status of their own shops. Many woodworking clubs all over the world also bought meters that they loan out to their members. After speaking with Roger Unger, Dylos founder and principal designer of this unit, I personally ordered and use the Dylos Pro 0.5 – 2.5-micron unit with the serial computer interface. We think these cut points give counts of the finest dust known to be the most harmful and cause deep damage in our respiratory systems.

    This unit really opens Pandora's Box on vendors still selling dust collectors and cyclones that don't move enough air to collect much of the fine dust and their fine filters just plain don't filter the finer particles. Enough fuss has been raised about the dangers of fine wood dust that many small shop owners now use these units. Hundreds have written me sharing their results. One of my engineer friends was one of the first to buy a meter. He found his home badly contaminated with wood dust from his basement shop. He tried lots of solutions and nothing helped until he installed an expensive Honeywell 0.3-micron allergy filtration system that works with his HVAC. His meter shows he cannot work safely in his shop without filling his home with huge amounts of fine dust, but at least his new filtration system rapidly reduces that airborne dust level. All report that venting their dust collectors and cyclones inside with standard filters immediately builds dangerously high levels of fine invisible dust. Most find that their so called fine filters freely pass the unhealthiest fine dust right through and actually become one of the worst sources of dust in their shops. Almost all with smaller than 3 hp dust collectors and under 5 hp cyclones report that their systems do not move enough air so let far too much fine dust into their shop air. Most find that their air cleaners take four to six hours to bring the fine dust level down enough that dust does not ruin their finishes, but these ceiling mounted air cleaners simply keep the finest unhealthiest dust airborne. Most find the only way to tame their fine dust problems is to vent their dust collectors and cyclones outside and keep a strong fan blowing outside. The widespread use of these meters has strongly validated what these web pages have been saying for years.

    Now, I am hearing from the electron microscope experts that wood dust is not just vanishing and quickly breaking down as was previously thought. Their testing and micrograph pictures show the closer we are downwind to commercial woodworking facilities that vent outside, the higher and more dangerous our exposure. Previously most thought that venting the finest dust outside let it disperse so quickly it did not have the concentrations to cause much harm. On one end of a valley in England a large pallet processing plant grinds up old wooden pallets. Most who live in a village on the other end of this valley a few miles/kilometers away have the same medical problems found in woodworkers who have high dust exposures. Moreover, because many of these pallets are old and have molding wood, so many have developed serious mold allergies. I suspect we will learn a lot more about fine wood dust as more measurement and attention gets focused.

    I think many now realize a number of things. Even just a little woodworking makes a huge amount of the most dangerous 10-micron and smaller invisible airborne dust particles. We get terrible dust collection unless our tool hoods to block the fast moving airstreams and control the fine dust. Even with upgraded hoods most basic tool designs still spew lots of dust so we have to provide higher airflows to surround our tools with a low pressure area to pull in this dust. Festool and Fein have already shown that tools built from the ground up with good dust collection built in get great collection with a powerful small vacuum. Until we can buy tools with this kind of dust collection built in we still need to upgrade hoods and move a lot more air. Testing over one hundred and twenty shops found not one dust collector under 3 hp or cyclone smaller than 5 hp moved enough air to pull in most of the fine dust. These larger airflows require 7" diameter duct and down drops unless the blower has been specially engineered to produce higher than normal pressures. Only one vendor, Clear Vue Cyclones is making blowers that can move the needed airflow through 6" ducting. These meters consistently show that every small shop vendor filter freely passes most of the unhealthiest dust. The major exception is Wynn Environmental. I personally use and recommend the Wynn "nano" filters with my dust collection equipment. Vendors have long known they can claim any level of filtering they want and prove their claims as long as they also don't include the airflow at any given filtering level. We can load up a chicken wire grid with enough rocks and dirt to provide a 0.3 HEPA level filter but it won't pass air. These meters give woodworkers two important tools. They can check the quality of their new filters and actually know when it is time to change out the filters because they have become worn out. These meters are also rapidly advancing our knowledge of how to get rid of the fine dust and keep it from building up in our shops.

    These affordable laser test units are not good news for me personally. They have helped grow my email volumes and number of telephone calls to overwhelming.

  8. Magazine Testing

    I had hoped that the magazine testing would take over the testing of dust collectors, cyclones and air quality. My keeping up that testing was too expensive and hard on my not so great health, plus I could not afford to fend off the nuisance law suits that kept threatening to pull down these web pages. My hope was to put out really good tests through a top magazine. I had already helped run two magazine cyclone tests and three dust collector tests. I worked closely with one of the most respected small shop magazines for over a year to do another full and far more complete round of dust collector testing and over a year more doing cyclone testing. I foolishly expected that these tests would share the dismally poor airflow and bad filtering which is near universal from small shop vendors to force these vendors to up the quality of their equipment.

    The dust collector airflow test results were the most accurate to date. The results were very poorly received by the small shop vendor community and many complained bitterly of sales being seriously hurt by those test results. Those tests showed almost every small shop vendor except Jet and Delta flagrantly lied on their advertized maximum airflows and actual working airflows consistently were under half of advertized airflows. Regardless, we found every 1 hp and larger dust collector moved ample air through smooth 4" duct to provide good "chip collection" which means cleaning up the same sawdust and chips we would otherwise sweep up with a broom. Of all the 1.5 hp and smaller dust collectors tested only the Jet and Delta 1.5 hp dust collectors moved a real 800 CFM if the collector was used with 6" duct and placed immediately next to our large stationary tool. Even that 800 CFM only meets OSHA air quality standards and fall short of the 1000 CFM that the experts found we must move at most stationary tools to meet the EPA and other higher air quality standards. This explains why we found no under 3 hp dust collector moved that real 1000 CFM. We also found the 3 hp dust collectors required use of all 7" duct to carry that much air as these blowers did not generate enough pressure to pull 1000 CFM through 6" duct when challenged by the overhead of a tool hood, short length of duct, and brand new clean filter.

    Our cyclone airflow tests were also the most accurate to date. We found no under 3 hp cyclone moved even the 800 CFM needed to meet OSHA air quality when challenged with only a new clean filter, short length of smooth duct and good well made open hoods. We only found two 5 hp cyclones that with these same challenges would move the real 1000 CFM that decades of expert experience and testing show we need at our larger stationary tools to get good fine dust collection. We found only Clear Vue cyclones could move this much air through 6" duct and down drops. All other cyclones lacked ample pressure to pull this much air through anything smaller than 7" diameter duct and down drops.

    Worse, unless these units are vented outside they are all worthless for good fine dust collection because the filters are too open and pass most of the finest unhealthiest dust. The magazine editor decided to not let publish either filter efficiency or for how well each unit pulled in the fine dust on a standardized test. My standardized test was simple but effective. I used a six foot long piece standard and readily available particle board shelving and made six cuts on a table saw that was upgraded with a good Lee Styron large over blade guard hood. Our particle meters show that hood works well if provided ample airflow. The change in weight of the particle board after cutting showed how much total dust was made. Each tested dust collector filter was clean and brand new. The change in weight of the dust collector or cyclone system after cutting showed how much total dust was collected. Dividing the particle board dust weight into the collected dust weight gave percentage efficiency. before use and after use. The difference in weight of the particle board after making nine cuts showed how much total sawdust was made. also test these units for how well they actually separated off and captured the fine invisible unhealthiest 10-micron and smaller particles.

    The cyclone testing went well, but also failed to test to see just how well these units actually separated off the fine dust. Unfortunately, that testing found every small shop cyclone except my cyclone design gravely failed the last set of magazine tests that actually looked at real airflow under real shop conditions. As a courtesy before the cyclone test article was printed, copies of the test results were shared with the participating vendors. Three of the largest cyclone vendors said they would not longer advertize in these magazines if that article was published. The magazine owners made a decision to kill that article editors to not share that last round of testing. I understand that no magazine would want to put out a review that showed their main advertisers as selling products with serious performance problems.

  9. My Testing
    1. Incentive

      Seeing that no new testing is expected in the near future, I chose to spend the considerable money it cost to buy and do some testing on my own. Before making these purchases I did quite a bit of research and had help from a number of experts who advised me on what test equipment to buy and what they said would make the most sense in terms of testing. Although I was not looking for laboratory results, I did want real numbers that others could see, duplicate, and understand in terms of how this affected their own shops. I also wanted all tested under real world working conditions instead of the long time magazine tests that have become a vendor game of who can move the most air under the most unusual test conditions.

      I bought an expensive test meter (See Test Equipment below) then tested many of my local friends' shops to get my testing protocol refined. My friends surprised me as quite a few had excellent dust collection mostly due to lots of careful work on their systems and making excellent custom tool dust collection hoods. In fact, the only dust collector that passed the relatively easy OSHA air quality standards belongs to one of my friends who vented outside. Some of my other friends also did excellent work with their smaller cyclones that they had either made or put together from commercial parts, but they had also totally remade their tool hoods to provide very tight fitting collection that let almost no air escape their blades, bits and cutters.

      I learned two importing things from testing my friends' shops. Regardless of how powerful their dust collector or cyclone, not one single shop passed their air quality test unless they had an upgraded over blade guard hood with dust port with a strong airflow. They had to either use a shop vacuum if they had a smaller port or use at least a 3.5" port if they were going to connect to a cyclone. The cyclones and dust collectors just did not have ample pressure to collect through a 2.25" to 2.5" small opening on a blade guard hood and provide much fine dust collection at all. I also sadly learned that the eBay sold cyclones and the one cyclone that failed so dismally in the last published magazine cyclone test could not be made to provide good fine dust collection no matter what we did. The add on to your dust collector cyclones from eBay used the same early cyclone design that almost all abandoned before 2003 because it added so much resistance it all but killed our blower airflows. This design actually works worse for 2 hp and smaller dust collectors than simply using a $25 plastic trashcan separator lid. That other vendor cyclone does not work nearly as well as a trashcan separator lid and plugs its filter so quickly it was recommended as something to not buy at all. The second very important thing I learned is every shop that I tested that vented inside had huge amounts of fine dust that just walking around stirred up enough to fail the more sensitive dust level tests.

    2. Volunteers

      An announcement was placed on two of the major woodworking forums asking for volunteers within the State of California willing to have their shop air quality tested. Quite a few volunteered to participate in this testing. Each was asked their brand, purchase date, and motor size of their cyclone. Each was asked if their cyclone supplier had advised them to upgrade any tool hoods or port sizes. Each was also asked if they had upgraded their table saw hoods with a dust collection port. Candidates were screened to omit all that had the eBay cyclones. None volunteered for testing that had cyclones from that vendor with such poor magazine test results. Candidates were further screened to ensure each different type of cyclone also included at least one shop with a table saw that used an upgraded blade guard with dust collection port. Each volunteer was advised of the test equipment to be used, asked for permission to make a small test hole in their main duct, and advised of what would be tested. Results would be shared with them after the testing and all people's identities would be kept private. Each was asked to do a little preparation work in advance of the testing.

    3. Testing Protocol
      1. Each shop owner was asked to do a little preparation to settle any airborne dust in their shop. Each was asked to thoroughly blow or vacuum out their shops then do no woodworking or shop cleaning for at least 72 hours prior to the testing and do what they could to minimize airflow in their shops from any source during that settling time.

      2. A baseline was set by testing the outdoor air quality.

      3. The inside shop air quality was then tested with nothing running and compared to that baseline.

      4. The cyclone was then turned on with all blast gates open and another air quality test was run before doing any woodworking.

      5. All airflow except to their table saw was shut off with gates or plugs. While the cyclone ran collecting only from the table saw the owner cut 54 linear feet of ¾" MDF using their standard blade with 1/8" kerf followed by another air quality test of the shop air.

      6. We then turned on any exhaust fans, air cleaners, opened available doors and windows, and ran the cyclones while doing ongoing air quality checks with the meter to see how long it would take to clear the air to below 0.1 mg/cm3.

      7. While the shops purged a 1/8" diameter hole was drilled into the main duct 12" before the cyclone inlet. A stand was then secured to the duct to hold a pitot air velocity sensor tube centered in the main duct. After the shop air had recovered a Dwyer Instruments 166-12 model calibrated pitot tube was inserted and attached to that stand. A Dwyer Instruments digital differential pressure meter was then used to determine system air pressure and velocity. That velocity was then used with the main ducting size to compute maximum air volume. All blast gates were then closed to measure maximum pressure and determine how much air was being leaked within the system. Blast gates were opened to test the airflow to each individual tool. All gates were opened to get the largest airflow. All airflows were recorded. The test hole in the duct was sealed and the shop owner was then given a summary of the results of their tests.

    4. Test Results

      I personally tested twenty nine shops in late 2005 and early 2006 with my testing growing to over one hundred and twenty total shops tested by 2009. In addition to my own tests, many of my professor and engineer friends did their own testing, most using exactly the same protocols. In total I received at least 300 more tests, many on the same dust collectors, cyclones and air cleaners.

      1. Filter Test

        Every cyclone and dust collector that vented inside except for those that used top quality commercial filters (specifically Donaldson-Torit, Camfil-Farr, and Wynn Environmental) immediately failed the first air quality test before doing any woodworking. Just turning on these dust collection systems without the good commercial filters instantly filled the shop air with huge amounts of fine dust. Every shop appeared to have been well cleaned prior to the testing. Our very sensitive particle counters registered the fine dust stirred up by just walking around and would have shown if these shops had buildups of fine dust. Clearly almost all the initial fine dust came from or through the existing filters. The airborne dust levels without doing any woodworking all exceeded the EPA and medical recommended maximum of 0.1 mg/cm3 range. Most averaged around the 1 mg/cm3 recommended by ACGIH. The worst was over the OSHA 5.0 mg/cm3 range. And this bad news was before doing any woodworking at all, just turning on the dust collection systems in a clean shop. Our particle counters showed all small shop vendor fine filters continued to freely pass the unhealthiest invisible under 10-micron particles as the particle counts for this very fine invisible dust did not appear to fall while just the cyclones ran. This indicates that in the up to a year that some of these shops had used their cyclones these filters had not "seasoned" enough to provide good fine dust filtering. Seasoning means building up a cake of fine dust in the filter pores that does not come out with normal cleaning.

      2. Dust Test

        Proper Hoods - No shop with a 2.5" or smaller port on their upgraded blade guard hood passed its air quality tests after cutting that 54 linear feet of MDF regardless of size or brand of cyclone. If we hooked up the Felder and identical Hammer over blade guards with 2.5" ports to powerful shop vacuums these units passed. No other blade guard worked even when hooked up to a powerful shop vacuum. Just like those saws with no blade guard hoods, the best of these hoods with the smaller ports still allowed the air quality to go well over twice the maximum airborne dust levels allowed by OSHA. The worst went to nearly five times the maximum airborne dust level allowed by OSHA. Air will not even hold more than this much dust unless pretty strongly stirred. Those that worked best had 3.5" and 4" openings on their blade guard hoods. In conclusion most hoods with small ports are near useless and even the best with small ports only work when connected to a powerful shop vacuum. We need 3.5" or larger ports connected to cyclones or dust collectors because these larger units do not have the pressure to pull enough air through a small 2.5" port.

        Ample Blower & Filter - None of the 3 hp and smaller cyclones were able to maintain the air quality at or below the ACGIH 1.0 mg/cm3 level or even the OSHA 5.0 mg/cm3 level. Only the one 5 hp cyclone that directly vented outside and the cyclones of my design actually maintained a shop air quality during and after cutting at the EPA and medical recommended 0.1 mg/cm3.

      3. Recovery

        Only those shops that either used Farr, Wynn, and Donaldson-Torit filters or provided a strong air cleaning effort with fine filters and or blasts of air going outside recovered quickly. All shops that stayed sealed with lesser quality filters did not return to outside ambient air quality levels unless we put a large commercial fan in a back door and opened the main door a little. Our particle meters showed within one half hour the large fan reduced the airborne particle counts to ambient (outside) and further testing showed there was no significant dust settling if a good fan was used.

      4. Air Volume Testing

        None of the 3 hp and smaller cyclones had a maximum airflow with all blast gates open much over 800 CFM. All 2 and 3 hp cyclones had a worst case airflow under 600 CFM to distant machines served by a 6" pipe. When serviced by 4" duct, down drops and flex hose airflows dropped to around 350 CFM. Every vendor supplied ducting design had air speeds in the main drop to well under the minimum 2800 FPM considered a minimum to avoid dangerous ducting piles. Every these vendor designed duct system built dust piles in horizontal runs and had plugging problems in the vertical runs. None were able to maintain the 3800 FPM minimum airspeed to ensure vertical duct runs stay clear. Only the 5 hp cyclones actually moved maximum airflows in excess of 1000 CFM with all ducts open. Only the Clear Vue Cyclones of my design and one other of the 5 hp cyclones actually moved a real 1000 CFM or better at the closest machine with a large duct and hood. All others moved under 1000 CFM at their largest single airflow machine. The lowest airflow machines all used vendor supplied ducting plans with even some of the 5 hp cyclones moving airflows well under 400 CFM due to totally inappropriately small down drops. All small shop vendor provided ducting designs had problems using 4" down drops for tools that require in excess of 800 CFM. No vendor recommended either replacing existing hoods, adding more ports, or opening undersized tool ports.

      5. Testing Summary

        Only the one other 5 hp cyclone vented outside and the cyclones of my design with good commercial filters actually moved ample airflow and to pass any of the air quality tests including the easiest to achieve Department of Labor, Office of Health and Safety Administration (OSHA) air quality tests. All 2 and 3 hp cyclones lacked ample airflow for good fine dust collection. All small shop supplied vendor filters also provided very poor filtering of the 10-micron and finer particles, plus stored up this fine dust and launched it all over our shops when these units were first turned on. All small shop vendor ducting designs had serious problems with providing ample air to our machines and most had problems keeping ample air moving to keep the ducting clear. Recovery time to restore breathable air quality required strongly venting outside or a combination of large air cleaner and cyclone with very good quality fine filters. My attorney told me to not release the specific vendor name and model numbers because I don't want the aggravation of another vendor threatened law suit.

        I believe the issues are the same that I have been pushing hard since 1999. Over twenty years of air engineering and refinement by the dust collection firms whose customers must pass regular air quality testing shows that for good fine dust collection we must collect the fine dust at the source and keep our shops clear of the fugitive dust that escapes collection. To capture the fine dust at the source we must first fix our tool hoods to control the fine dust, move ample air to collect this dust, and then get rid of that dust by blowing it away outside or amply filtering before returning the air to our shops.

  10. Test Equipment

    Met One Aerocet 531

    2000 - The Aerocet 531 was introduced to the market. The Aerocet 531 combines particulate and mass measurements in a single small hand-held instrument with easy to use data logging.

    Particle Mass Profiler and Counter in a Single Handheld Unit
    The Aerocet 531 is a small, handheld, battery operated, and completely portable unit. This unit provides both particle counts and mass PM measurements as stored data logged values, real-time networked data, and can give printed results.

    Five Mass Ranges and Two Particle Sizes
    All five important mass size ranges (PM1, PM2.5, PM7, PM10, and TSP) are displayed in mass mode as well as two popular cumulative particle sizes (> 0.5 and > 5.0 microns) in particle mode.

    Tailored Mass Conversion
    The particle counts from eight size ranges are converted to mass using a proprietary algorithm for typical-density aerosols. Accommodation for special particulate with different densities is provided through user-programmable "K-factors."

  11. Data Collection Forms

    Air Flow Test Form

    Air Flow Test Form

    Air Flow & Air Quality Testing Spreadsheet (MS Excel)

Copyright 2000-2015, by William F. Pentz. All rights reserved.