Table of Contents
(click on topic to go there)
- Airborne Dust Definitions
- Airborne Dust Volumes
- Airborne Dust Life
- Airborne Dust Collection
- Probability of Harm
Innumerable people have asked over the years why continue to provide the research, time and money needed to keep up these Cyclone and Dust Collection Research web pages. The answer is simple. I don't want to see other small shop users blindsided like I was.
Although cleanup of wood dust, shavings, curls and chips known as "chip collection" remains important to avoid fires, slipping, and being able to see as we work, I painfully discovered the dangers of invisible fine dust. I used the top magazine rated cyclone based dust collector with vendor designed and supplied ducting plus vendor recommended upgraded filter. That system worked poorly but left a clean looking shop that created a bad false sense of security. I landed in the hospital from a bad wood dust triggered allergic reaction. My respiratory doctor had me spend my down time learning about fine dust. This web page gives an introduction and overview of what I learned. The other pages provide much more detail. I discovered my cyclone system and every other small shop dust collection system pumps out so much fine dust that we are slowly ruining our lungs and as happened to me we can easily have other more immediate serious reactions.
Three months later my health was not improving so my respiratory doctor convinced me to pay for expensive certified air quality testing. That testing showed fine wood dust particle counts in my shop and home thousands of times higher than the EPA considers safe. With inexpensive particle meters now readily available thousands of woodworkers all over the world share that when we vent dust collection systems inside, fine filters or not, we build up dangerously high amounts of fine invisible dust. I consistently hear that just walking around in clean looking shops stirs up dangerously high amounts of fine dust. Wood dust unless it gets wet last nearly forever, woodworking makes far too much fine dust, and our dust collection systems miss collecting far too much. This dust that escapes collection is known as fugitive and it often rapidly builds to dangerously high levels. Government air quality testing found that a couple of hours working in a shop that vents its dust collection inside gives us more fine dust exposure than workers in a commercial shop that vents outside receives in months of full time work. Because this fine dust behaves like a gas and spreads into any connected airspace almost all homes that do woodworking inside or in basements, and homes connected to garage based shops also test with dangerously high airborne dust levels. After decades of taking care of woodworkers and our family members for wood dust generated health problems often worsened by our using fairly toxic woods my respiratory doctor says small shop workers should make fine dust collection a top priority.
- Airborne Dust Definition
The Airborne Dust Sizing picture on the left compares an average human hair of about 70-microns thick to 30-micron, 10-micron and 2.5-micron dust particles. A single micron is one millionth of a meter and a meter is about 39" long. By definition airborne wood dust particles consist of particle material (PM) smaller than 30-microns. Researchers and health experts work with fine dust so much they abbreviate fine dust as PM short for particulate material followed by a particle size number. PM-10 is shorthand for particles smaller than (<) 10 microns, PM-5 for those sized under 5-microns and PM-2.5 for those sized under 2.5-microns. Fine dust consists of airborne dust particles sized under 10-microns. Medical professionals call these same under 10-micron fine dust particles inhalable dust because these particles get right by our natural protections and get inhaled deep into our respiratory systems.
Most large woodworking facilities either use fairly open filters or cyclone separators to remove the heavier sawdust and chips then vent their airborne dust away outside. When blown outside into normal outdoor air currents airborne dust particles vanish with no visible trace and quickly break down when they get damp. Most large commercial woodworking facilities vent outside because it is safer and less costly than filtering. The problem is woodworking just makes far too much airborne dust that quickly loads up and ruins fine filters. OSHA testing shows airborne dust makes up roughly 5% of the woodworking sawdust we make, so every twenty pounds of sawdust contains about one pound of airborne dust. This does not sound like much, but it only takes a few pounds of airborne dust to plug a fine filter enough to badly reduce airflow. Without airflow our dust collection systems do not work. This means fine filters need constantly cleaned, but cleaning fine filters quickly ruins them. Airborne wood dust particles have razor sharp edges and sharp often barbed points. When we clean by shaking, vacuuming, or blowing a blast of compressed air at our filters, these razor sharp edges cut and tear their way through the very fine strands that make up our filters. Soon our filters no longer provide fine filtering. Most commercial shops that use fine filters have to replace their filters every three months of full time woodworking.
- Airborne Dust Volumes
How much fine dust we make is scary. When viewed by an electron microscope wood looks and behaves like a big stack of glued together very fine glass tubes. Much of the strength in wood comes from silica which is better known as glass. Every time our hand and power tool blades, bits, cutters, scrapers and even sandpaper touch wood, at the point of contact these very fine tubes explode into billions of razor sharp particles often with sharp barbed points. A particle meter shows even cutting a long perfect shaving with a really sharp hand plane that makes no visible dust generates huge numbers of fine dust particles. OSHA testing shows on average wood dust is fairly evenly distributed by particle size. This means airborne dust which consists of particles sized under 30-microns has roughly even weights of 0 to 10-micron sized particles, 10 to 20-micron sized particles, and as 20 to 30-micron sized particles. This equal weight distribution makes for a huge difference in the numbers of small to large particles. It takes 27,000 one micron sized particles to equal the weight of just one 30-micron particle. In short working wood generates so many fine particles that instead of counting, most measure particles and set standards by weight rather than particle counts.
Few realize just how much fine dust our woodworking makes compared to how little it takes to build dangerous air quality. OSHA testing shows we get about 5 pounds of airborne dust out of every 100 pounds of sawdust made. This means half of an average dust collector bag which contains about twenty pounds of sawdust ended up with our making about one pound of airborne dust. Because the dust is equally distributed by weight one third of the one pound of airborne dust consists of fine dust particles sized under 10-microns. One third pound is 5 1/3 ounces. Because there are 28349.5 milligrams per ounce that means every twenty pounds of sawdust we make creates 151,197 milligrams of fine dust. A typical two-car garage sized shop is eight feet tall, seventeen feet wide, and twenty-five feet long for a total volume of 3,400 cubic feet of air. Multiply by 0.0254 to convert to cubic meters which shows a typical two-car garage sized shop contains about 96.28 cubic meters of air. Round up to 100 cubic meters to make the math easier. The medical problems caused by fine dust are so severe that the EPA allows a maximum of 0.1 milligrams of fine dust per cubic meter. That means our typical 100 cubic meter two-car garage sized shop fails its EPA air quality test as soon as 10.0 milligrams of fine dust goes airborne. One of my engineer friends said, Slapping a dusty shop apron launches enough fine dust to cause a typical small shop to fail its EPA air quality test". Since we make 151,197 milligrams with every twenty pounds of sawdust, that is enough fine dust to cause 15,119 (151,197/10) average sized shops to fail their EPA air quality tests. Careful testing of almost every current small shop dust collector and cyclone system shows the very best still miss collecting up to 40% of the fine dust made. Even if they were 99% efficient as some vendors falsely advertize, out of every twenty pounds of sawdust every 1% of the fine dust missed adds enough extra dust to our shop air to cause over one hundred and fifty one more shops to fail their EPA air quality tests.
- Airborne Dust Life
The really bad news is fine dust can last centuries, so most who get ill from fine dust are blindsided by the huge amounts of built up fugitive that previously escaped collection. Wood gets much of its strength from silica which is better known as glass. Unless wood gets wet it does not pull in the organisms that break wood down, so fine dust lasts as long as it stays dry. To the right is an electron microscope image of wood dust found when a pyramid was opened that had been sealed for thousands of years. Hoping fine dust simply breaks down and vanishes quickly is pretty wishful thinking. If we are venting inside and have a 99% effective system, we are still pumping into our shop one hundred and fifty one times more fine dust than it takes to fail an air quality test. With even the best systems passing far more dust, those with particle meters consistently find that most shops that vent inside, even when the shops look very clean, have so much built up invisible fugitive fine dust that just walking around stirs enough dust airborne to fail an air quality test. This dust build up is why I constantly recommend venting outside or into really fine filters.
- Airborne Dust Collection
Many wrongly think it is easy to collect fine airborne dust but it is not. We know the lightest breath easily moves airborne dust highlighted by a beam of sunlight, so wrongly believe our powerful dust collection blowers and vacuums should do a great job. They do not and you already know why. Try moving the same highlighted airborne dust by sucking through a straw. You cannot with the amount of air our lungs move unless you get the straw right next to each particle. The problem is sucking pulls air from all directions at once so airspeed drops at roughly twelve times the distance squared (4*Pi*r*r). We already know about this. When on blow our shop vacuums can move dust all over, yet when they suck they only pick up when the collection nozzle is right next to what we want to collect.
Many decades of research and experience by those firms that guarantee customer air quality shows what we must do to get good fine dust collection. They found woodworking makes so much dust the only way to ensure passing air quality tests is to collect the fine dust as it gets made. They found unless we totally enclose the working areas of our tools, we need hoods that block and control the fast moving air streams. We need good hoods because dust collection blowers move air at under fifty miles an hour and our blades, bits and cutters often launch dust at over one hundred miles an hour. If our hoods don't block, control and capture that fast moving dust, we lose. They also found woodworking creates so much fine dust that exhaust fans and air cleaners cannot lower the airborne dusts levels fast enough to keep from failing air quality tests. They found to amply collect the fine dust in addition to good hoods, we also must build a "bubble" around the working areas of our tools. The air speed inside this bubble must be at least fifty feet per minute out to fifteen and a quarter inches in all directions or normal room air currents will blow the fine dust all over before it can be collected. It takes a lot of air to build this big of a bubble, right at 1000 cubic feet per minute at each small shop stationary tool. It takes a 3 hp dust collector or 3.5 hp cyclone to move this much air assuming clean new filters and large sized ducts. Because 3.5 hp motors are not readily available, most need 5 hp motors to power their cyclones. Without this much airflow, woodworking makes so much dust that even venting outside misses collecting considerable dust because our dust collection systems do not amply stir the air enough.
Meanwhile our small shop vendors do not help at all. They are in a life or death competitive struggle. Most would rather buy a 1.5 hp dust collector with a "fine filter" than step up to three to four times more cost to buy a 3 hp dust collector or 5 hp cyclone, especially when the dust collector leaves a clean looking shop. All dust collectors and traditional cyclones do a terrible job of separating sawdust. Almost all dust collectors blow sawdust particles up to 100-microns right into the filters. All traditional small shop cyclones pump close to 100% of the airborne dust right through. This puts so much dust into fine filters that these filters need constant cleaning. As discussed before the more and deeper we clean our filters the less time they last. At typical cyclone loading commercial shops that use fine filters must replace them every three months. At an average cost of over $200 per set of small shop filters, most small shop owners will not accept a system that requires constant filter changes. If our vendors instead give us filters that freely pass fine dust sized particles, then their filters take much longer to get dirty, need far less cleaning, and last for years instead of months. Sadly, regardless of what they advertize our small shop vendor community almost all sell filters so open that they provide almost no fine dust protection.
Fine dust rapidly contaminates our shops and can also fill our homes, vehicles and any areas we visit. Unlike larger airborne dust particles that quickly settle in indoor air, fine wood dust particles are so light that normal room air currents overcome gravity and keep this dust airborne except in very still air. This means fine wood dust behaves similar to a gas or bad odor to rapidly spread to evenly fill all available air. This is why basement and in-home shops almost always badly contaminate the rest of our homes. Fine dust also readily travels in our hair, on our skin and on our clothes, so as woodworkers we often contaminate our homes, offices, vehicles, and other areas we visit when still wearing our shop clothes. My own home was terribly contaminated and it connects to my garage based shop with a self-closing door. Just about any air movement will launch fine dust airborne again then keep the fine dust particles suspended airborne.
Risks define what can happen and fine dust poses many risks discussed in detail on the Medical Risks page. We are constantly exposed to considerable fine dust in our daily activities. Our bodies do a good job of eliminating larger dust particles, but fine airborne dust particles get right by our natural protections. The finer the particles the deeper into our respiratory systems they go and more harm they cause. Fine wood dust particles have razor sharp edges and sharp often barbed points that cut, tear, stab and jam these particles stuck deep in our respiratory systems. These lodged particles cause swelling and scaring that reduces our airflow. A Google search on PM health risks gives over forty four million references. The Internet has considerable innacurate information, but that peer reviewed medical information verified by expert physicians shows every exposure to fine dust of every type causes a measurable loss of respiratory function, some of this loss becomes permanent, and the greater and longer the exposure the higher the damage. Over time this damage builds into chronic obstructive pulmonary disease (COPD) meaning our lungs get so damaged we cannot breathe well. This danger is so high that the EPA sets their indoor air quality standard at fine dust levels of below 0.1 milligrams per cubic meter of air and they can close office buildings if the dust level goes over.
Worse, fine wood dusts contain and carry toxic chemicals that when trapped in our lungs causes serious short and long term health problems. We should always check a good wood toxicity table before using any wood because the dust we inhale can contain chemicals which are poisonous, strong irritants, sensitizers meaning they cause us to build ever stronger allergic reactions, and can increase our risk of cancer. Also, wood dust often carries many other chemicals from glues, finishes, fillers, insecticides, preservatives, molds, yeasts, mildews, etc. that can be present without our knowledge and can harm our health.
- Probability of Harm
We need to know the odds of anything happening to us to decide how much if any protections we need. The damage caused by fine dust depends upon overall health, genetics, type of exposure, amount of exposure, frequency of exposure, and duration of exposure. The higher, longer and more frequent our exposure the greater the harm. Doctors call this a dose response relationship. Almost all medical studies that give probabilities studied health insurance data for woodworkers in large facilities that vent their fine dust away outside. The health insurance data show at typical exposure levels for shops that vent outside 100% of workers develop a significant loss in respiratory volume of roughly 1% capacity loss per year of woodworking, about 14% are forced into an early dust related medical retirement, about 7% develop such bad sensitivity (allergies) that they must permanently give up woodworking, and a tiny number develop dust related cancer. For the large facilities that voluntarily meet the Department of Labor, Office of Safety and Health Administration (OSHA) recommended air quality standards the number forced into an early fine dust related medical retirement drops to about half, meaning one in seven is forced into an early dust related medical retirement. This is really bad news for small shop workers because we average much higher exposures. Although we found no medical studies run on small shop workers, my respiratory physician said his experience from decades of practice convinces him that small shop workers, hobbyists, our families and even our pets often suffer the most from fine wood dust triggered health problems.
Almost every small shop dust collector, cyclone, air cleaner and shop vacuum at best provides a clean looking shop that creates a bad false sense of security. Small shop vendors compete in a very aggressive market. The cost to provide fine enough filters and ample airflow is triple what it costs to provide good "chip collection". As a result most vendors sell chip collectors and add fine filters and advertize fine dust collection when they have neither the needed filtering or airflow. Without ample airflow and large enough fine filters these systems may leave us with clean looking shops, but they miss so much of the fine invisible dust that they should be called "dust pumps" when vented inside. Most who vent these systems inside build such dangerously high fine invisible airborne dust levels that their shops fail EPA air quality tests from just the dust we stir airborne from walking around. In short unless we also blow a fan outside most small shop workers and even hobbyists that spend minimal shop time get more fine dust exposure in a couple of hours than those in facilities that vent outside get in months. Since most commercial full time workers who have far less exposure, this is not good news for small shop workers.
Dust Collection Basics