Frequent exposure to large amounts of wood dust can lead to sinus and lung problems, or worse. And it's the finer dust particles-those smaller than 10 microns-that are the most hazardous. To put that size in perspective, consider that a human hair is about 100 microns thick, while airborne dust particles smaller than about 20 microns are invisible to the naked eye.
Our lungs have a built-in cleaning system that works efficiently under most conditions to protect delicate tissues from the damage fine dust causes. The trouble starts when your respiratory system must deal with large amounts of "respirable dust" (below 10 microns). Heavy exposure to this dust can overwhelm the natural defenses and lead to inflammation and swelling of the airways, which cause symptoms such as shortness of breath, increased sputum and coughing, frequent colds, nosebleeds. sinus trouble or bronchitis.
Also, wood dust may contain allergens and toxins such as pesticides, fungi (molds) and chemicals which can trigger allergic reactions. (Many tropical hardwoods can be especially irritating, and Western red cedar can cause allergic asthma.)
How Much Dust Is Too Much?
In an industrial setting, it doesn't take much dust to be considered harmful by OSHA. Their current regulations limit dust concentrations in air to an amount equivalent to about three teaspoonfuls dispersed in an 800-square-ft. shop with a 10-ft. ceiling.
But in the home shop, if you only work a few hours a week and don't do a lot of sanding or other operations that produce fine dust, you probably don't have too much to worry about. On the other hand, if you spend long hours in the shop several times a week doing a lot of cutting and sanding without adequate dust collection, you may be at risk for respiratory disease.
A dust collector fitted with highly efficient bags will be able to capture much of the dangerous dust down to 5 microns, so this is your best form of protection from the general problem of dust. If you have particular allergies or severe reactions to wood dust, try augmenting your dust collector with a recirculating air filter (see main article), or a PAPR (Powered Air Purifying Respirator), also known as a dust helmet. (See aw #33.) The best of these can filter out dust down as small as 0.03 microns.
I don't recommend cheap paper-filter dust masks as protection, but they're better than nothing if you can get one to fit well. (They don't work with beards.) If you plan to use a disposable mask, choose the kind labeled for toxic dust, instead of one labeled for nuisance dust.
Finally, If you develop any of the symptoms of excessive wood dust exposure listed above. I'd advise you to see a physician knowledgeable in occupational medicine.
DR. IMBUS is a board-certified physician in occupational medicine who acts as a consultant to the woodworking industry.
work more efficiently and not fill up as fast.
• If you're highly sensitive to dust or if you're concerned about its long-term health effects, look for a collector with filter bags that will trap dust down to 5 microns or smaller.
• Whenever possible, buy the largest filter bags available for a collector. (See Sources, below, for extra-large bags.) Many collectors come with undersized filter bags that constrict air flow, A rule of thumb is that the bag's fabric area in square ft. should equal the system's CFM rating divided by 10. (For more information on interpreting manufacturers' CFM ratings, see page 53.)
Once you've chosen a dust collector, you can improve its efficiency by following these tips:
• Empty waste bins and filter bags when they are half-full. Hie closer a bag is to empty, the more usable filter area it will have and the better it will filler dust.
• Construct dust collection hoods for your machines and place them as close as possible to blades and cutters to help focus suction on the dust.
• Improve suction by sealing the bases of enclosed I^H^fl machines like cabinet saws and plugging holes or seams with strips of old rubber inner tube, weather stripping or duct tape, r* •Improve suction on portable power tools j by buying and using the optional vacuum ports many manufacturers offer. ▲
DAVE SELLERS is an assistant editor of aw.
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