This article summarizes my woodworking dust collection experience and research.
My Background
I have been woodworking with hand and power tools since 2001. I learned a lot about workshop air quality from the Australian Dust Extraction forum, particularly from Bob Loss (username BobL). Bob’s academic research included clean room technology and he has implemented many air quality solutions for Men’s Sheds. His experience, scientific expertise, and clear writing make him a terrific advocate for workshop air quality. I am trying to summarize what a learned from Bob and others on the forum for a North American audience.
The Danger
Inhaling wood dust can cause decreased lung capacity, allergic reactions, and even cancer. Read a good summary from the Canadian Centre for Occupational Health and Safety.
In addition, particulate matter of any type can get deeply embedded in your lungs and into your blood stream, causing heart and lung problems. The smallest particles are the biggest problem. Read more from the US Environmental Protection Agency.
Accessing Your Risk
I’m just a guy on the internet, but here is what I gleaned from accessing my own risk.
We care most about two measurements:
- PM2.5 - particles less than 2.5 micrometers
- PM10 - particles less than 10 micrometers
Both measures are expressed in micrograms per cubic meter (μg/m3). In other words, mass of dust over the volume of air.
PM2.5 particles are the most concerning and are too small to see:
The goal is to keep these tiny particles out of your lungs. Factors to consider:
- Size of dust generated. Tiny dust from sanding is the worst, but any power tool is bad.
- Exposure time. If you are in the workshop every day, then you are at higher risk.
- Workshop size. One cut of a compound miter saw in a 10x10 shed will make the air much dirtier than the same cut in a 30x50 workshop. Ceiling height also matters.
- Shop ventilation. Tiny particles will stay suspended in the air for days in a closed shop.
- Your body. Do you have heart or lung issues? Are you older? Do you have allergies? All these increase your risk.
All PM2.5 particles pose a health risk. Wood, and the mold and fungi that come with it, have an added risk of allergic reaction. Your allergy can worsen over time and prevent you from woodworking at all.
Start by measuring
Start by assessing your current dust exposure.
Do you have have a layer of fine dust in your shop? Those particles fell out of the air, so you were breathing them. Clean up that dust because it will become airborne when disturbed.
How does your body react? After working in the shop, does your mucus or congestion change? That’s a sign that your lungs are processing dust. When I use a compound miter saw to cut white (spruce, pine, fir) 2x4s without wearing a mask, I will be more congested the next day. Pay attention to your body, but don’t assume lack of reaction means everything is fine.
To see the invisible dust, I use a particle monitor:
My sensor is sold under a variety of names on Amazon and Aliexpress and looks like a science fair project. It uses a Plantower PMS5003 sensor and is much less expensive than a Dylos, but roughly equivalent. “Real” PM2.5 monitors cost thousands of dollars and are very temperamental, so don’t expect high accuracy from these home-use sensors. The scientific article “A Review of Low-Cost Particulate Matter Sensors from the Developers’ Perspectives” is readable and has more details. The article says calibration is required for accuracy. I compare an outdoor reading from my monitor to the PM2.5 readings from the AirNow website and app; my reading is usually low.
Relative measures from my particle counter have taught me many things, including:
- Sweeping increases the particle count dramatically.
- Belt sanding in a closed shop with no dust collection increased the particle count for weeks until I blew out the shop with a leaf blower.
- Sucking in outdoor air can decrease air quality. When that happens, I check AirNow.
The sensor can get clogged. Protect it from airborne finishes and extremely dirty air. I don’t leave mine running.
Humidity impacts the readings and the humidity reported by the sensor is consistently high. I do not know if that matters.
Now that you can (sort of) measure the problem, start working on solutions.
Work Outside
I use portable power tools like my router, random orbit sander, track saw, and compound miter outside the shop. Wind blows away the fine dust. More importantly, fine dust will not be trapped inside my shop. I recommend wearing a dust mask.
Vent Outside
Sucking air out of your shop is a very effective way to remove fine dust.
WARNING: If your shop shares air space with a combustion appliance like a gas furnace, gas water heater, fireplace, or wood burning stove, you cannot vent outside. Forced ventilation will suck poisonous combustion gases down the flue and into your workshop.
If your shop is climate controlled, venting outside will remove your cold or warm air. Air has very little thermal mass. Your heavy tools will help it return to an indoor temperature. The longer the fan runs, the more it is like working outside.
Despite this drawback, venting outside is a very cost effective way to atone for many dust collection sins.
Add Cross Ventilation to Your Shop
PM2.5 is a measure of mass of dust over air volume. Use cross ventilation to dramatically increase the air that carries dust and the PM2.5 level will improve.
Air should flow through your shop with an inlet at one end and an outlet at the other, ideally with 20 air changes an hour. Use multiple exhaust fans to prevent dead air spots.
Remember the combustion gas warning above.
Vent a Two-Bag Collector Outside
Collecting dust at the source is the first choice. A two-bag collector vented outside can do that.
A Powermatic PM1900 is a good choice because it has a 14" impeller. Felder AF22 is another. A unit with a 13" impeller is acceptable. I see used units for sale relatively often.
Two choices:
- Build an air tight enclosure around the collector and vent the enclosure outside.
- Move the entire unit outside, protected from the elements, and run a duct through the wall into your shop.
This also puts the noise outside.
Use 6" ducts.
Compare units using impeller size, not motor horsepower. The motor needs enough horsepower to turn the impeller. Beyond that, a larger motor makes no difference.
Since you are venting outside, you can use 30 micron bags.
Remember the combustion gas warning above.
Exhaust a Cyclone Outside
A cyclone can also collect dust at the source.
You want at least 1000 real CFM, which means a big cyclone like a ClearVue CV1700, which you can order without filters. Oneida will also sell without filters.
For equivalent air flow, cyclones are more expensive than two-bag collectors because the cyclone requires a larger impeller, more powerful motor, and cyclone body. If you are willing to clean the filter, a good two-bag collector would be fine.
Use 6" or larger ducts, sized for your cyclone.
I chose a cyclone vented outside, which I documented on the Dust Extraction forum.
Remember the combustion gas warning above.
Exhaust Cyclone Inside Through a Filter
If venting outside is not an option, then use a large cyclone with filters like a ClearVue CV1700.
You will want to measure:
- PM2.5 using one of the meters above and
- static pressure of the filter with an Oneida Real-time Filter Efficiency Gauge Kit or similar.
If your system leaks or the filter has holes, it will blow dirty air into your shop.
The filter catches fine dust not removed by the cyclone. Over time the filter will clog. I told a friend with a big sander that filter clogging was a concern. He didn’t believe me because he bought a ClearVue, but he cleaned his filter anyway. When he started his cyclone, he could hear material traveling through the ducts from all over his shop. The airflow had increased significantly.
Use 6" or larger ducts, sized for your cyclone.
A cyclone with a filter can also serve as a very powerful (but loud and expensive to operate) air cleaner.
Other Possibilities
Managing workshop air quality involves a lot of compromises. The best options above involve pulling outside air into your shop, spending a lot of money, or both. It is natural to want other options. The problem is the other options are not as effective.
To collect fine dust at the source, shoot for 1000 CFM of actual air movement. That requires 6" ducts and a powerful blower.
Using a 2HP Collector
The Australian Dust Extraction Forum has an entire section on modifying an 2HP dust collector for better performance. These collectors are attractive because they are inexpensive and run on 120 volt electricity. At the end of your efforts, you will have a sub-optimal solution, but if it is all you can accommodate right now, then don’t worry about it and get to work.
Remember that cyclones and chip separators rob the system of static pressure. With a 2HP collector, you will need every bit of static pressure you can get, so avoid a separator. Cyclones decrease airflow.
Using a Two-Bag Collector Inside
If you must vent a two-bag collector inside, then use pleated canister filters instead of bags. The canisters clog less because they have more filter media. You will need to clean the filters regularly. These systems often leak, so monitoring the indoor air quality and filter performance are both important.
You are probably tempted to add a cyclone like a Super Dust Deputy. However, cyclones decrease airflow and this unit is sized to work well without a separator. If you want a cyclone, then save up for an entire cyclone unit.
Short Cyclones
Several companies, including Laguna, Jet, and Grizzly, sell all-in-one units that roll around and include a short-cone cyclone and filter. In general, the taller a cyclone, the better it separates dust from the air. These short units rob the system of static pressure with poor separation, so expect the filter to clog very quickly from fine dust.
However, you can vent a short cone cyclone outside and are unlikely to see dust outside as a result.
If you leave the filter attached and roll the unit around, you can dramatically decrease the need for duct work.
Wearing a Mask
I have a mask and I use it.
Dust masks help avoid breathing dust during messy operations. I recommend a P100 mask such as the one by GVS. The mask works well outside or when waiting for the air in your shop to be cleaned up. I don’t consider it a substitute for dust collection because the fine dust stays suspended in the air for days, so you must treat your workshop like a hostile environment and wear the mask 100% of the time. That seems unlikely.
An N95 mask like the 3M Aura is more likely to leak than a silicon P100, but that is another option.
Air Cleaners
I made a Pentz style air cleaner. It is very effective at cleaning the air after all dust has been collected at the source. Clean up the visible dust in your shop, collect all the dust you can at the source, and then use the air cleaner.
I also run my air cleaner when using non-electric hand tools.
Use 6" Ducts
Nearly all the dust collection paraphernalia uses 4" ducts, but use 6" ducts. Their cross sectional area is 2.25x larger. Moreover, at the same pressure, a 6" duct carries about three times as much air.
The ducts should have as few turns as a little flex hose as possible.
When the 6" pipe arrives at your machine, you can split it into multiple connections like many bandsaws have. You can also enlarge the port. Here are some examples.
For now, just try to get 6" ducts to your machines.
Measuring Airflow
Accurately measuring airflow is a challenge. Using a propeller anemometer at the end of an open pipe will produce bogus results. If you see a YouTube personality doing that, they don’t know what they are talking about. For a more accurate measuring method, see the Dust Extraction forum.
I use a Testo 405i hot wire anemometer in a 5’ length of 10" diameter duct. Ideally the length would be longer, but dust collection is a long series of compromises.
A Word on Specifications
Most companies grossly exaggerate airflow numbers. If a dust collector has one number like “1300 CFM,” then it is an exaggeration. To get real numbers, you need a fan curve, which documents airflow at several different static pressures. Oneida, Grizzly, and Laguna all publish fan curves for many of their products. Ironically, ClearVue does not.
All these products obey the same laws of physics, so if you find a fan curve for a similar system and impeller size, then the two fan curves are likely to be similar.
Static pressure losses in duct work adds up quickly, even when you follow the guidelines of using 6" pipe and minimizing turns and flex hose. Don’t assume you will be operating at the top of fan curve.
Summary
The title of this article is “Reasonable Small Workshop Dust Collection” and now that you have read all the way to the end, you may not consider any of these solutions reasonable.
Dust collection is expensive, so you may have to make compromises.
No matter what, you are dealing with an invisible foe, so use the monitoring techniques above to measure your progress.
Do the best you can. You are worth it.
Questions?
Ask on the Australian Dust Extraction forum. (Check the FAQs first.)
