How Much Dust Is Too Much?

Dear Wood News,
The U.S. Department of Labor Office of Safety and Health Administration (OSHA) has determined that exposure to airborne wood dust from Western Red Cedar in excess of 2.5 mg per cubic meter of air and to dust from any other woods in excess of 5 mg per cubic meter is hazardous to your health, and has ruled that General Industry must keep exposure in the workplace below these limits.

It's interesting to note that OSHA considers wood dust exposure more hazardous than exposure to Chloroform whose mg per cubic meter limit is 9.78; or Carbon Monoxide at 40; or Turpentine at 560; or VM&P Naptha at 1350; or Acetone at 1800.

There is no requirement that hobbyists comply with these limits in their home shops, but it would benefit their own safety and that of others in the home, especially kids.

I would be interested to know, and I think your readers would also, how much airborne wood dust is 5 mg per cubic meter?

Sincerely,
R.S.L.

We're not exactly ready to rush out to the workshop laboratory and measure out a government-approved five milligrams of wood dust, but we can illuminate the subject at least dimly as follows: 5 mg equals less than two ten-thousandths of an ounce. According to OSHA standards, a moderate-size woodworking shop, 15 by 30 feet with ten-foot ceiling, will reach the permissible exposure limit (PEL) when there are two hundredths of an ounce of wood dust in the air. Egad, Pogo, that's not much dust! (A dime weighs eight hundredths of an ounce.) If anyone happens to know any intelligible details on this subject, such as how OSHA defines dust, how visible dust is at 5 mg/cubic meter, and can you even turn on a sander or a planer or a router without going over the PEL, please let us know.

These standards might sound absurdly strict and downright unrealistic, but they do make one fact quite clear: the people charged with keeping workers safe in the workplace think that wood dust is very bad for you. Most of us won't have any trouble agreeing with that, having experienced plenty of clogged lungs, wood-toned sinuses, bleary eyes, sore throats, allergies and other assorted ailments traceable to breathing in the average shop. We also know that a dusty shop is indirectly hazardous to the occupants' well-being; though most us don't even want to be conscious of it, the direct health effects together with the physical inconvenience of a dirty shop add a constant background of stress to an activity that doesn't need that at all, for the hobbyist or professional alike.

Almost every shop could do a whole lot more to reduce the amount of dust allowed to get into the air. Some tools, like most hand-held routers for instance, present really difficult dust control problems because it can be nearly impossible to collect very much of the waste at the source; once dust gets into the air, only powerful whole-shop filtered circulation or exhaust can relieve the problem. Many tools, though, allow the user to hook up a dust collector or shop vac right at the source and eliminate most of it immediately, and more and more tools are coming equipped for efficient dust collection.

Sooner or later a good dust collection system becomes an inescapable necessity in the well-equipped shop. A lot can be accomplished with a good shop vac and a little ingenuity, but the vac reaches its limits when dust is accompanied by huge quantities of solid waste, such as comes from a thickness planer, or when the dust source area is greater than a few square inches, such as under an open-stand tablesaw or jointer.

Highland Woodworking is proud to sell the finest shop vacs available today,
Festool Dust Extractors.

Even a shop with vacuum ports on every tool and a dust collector in fulltime operation is still going to run well over OSHA's guidelines in many situations. It's a good idea to have a simple filtered-fan arrangement set up to routinely clean all the air in the shop. Running at low speed so as not to unduly stir up dust that's already settled out, an inexpensive window fan moving air through a couple of furnace filters will gradually and effectively remove very fine dust which would otherwise remain suspended for long periods.

Readymade solutions are also available, including our
Rikon 62-400 Air Filtration System.

Finally, anyone who works wood with any tool more aggressive than a whittling knife needs a good dust mask, and should automatically put it on whenever a machine is in operation, and keep it on until there's no dust left in the air (or at least less than 2 ten-thousandths of an ounce per cubic meter).

Lots of folks think dust masks are a nuisance, but would you really rather have bronchitis, or dust pneumonia, or hypersensitivity to rosewood or some other shop horror? Inexpensive one-strap paper masks don't seal well enough to offer good protection in the shop, but heavier and costlier two-strap disposables work quite well. The only drawbacks to these masks are replacement cost and non-selective breathing -- that is, you breathe out as well as in through the filter medium. When you're working hard and breathing hard, water vapor in your breath dampens the mask, causing it to lose its shape, load with dust and become hard to breathe through.

Inexpensive plastic masks with replaceable filters may be a good choice if you find one that happens to fit your face and seal well; sometimes you can improve the fit with a bit of stick-on weatherstrip or other custom alteration. Using a paint-spray respirator with the chemical cartridges removed isn't all that great an alternative because the masks are hot, bulky and not especially easy to breathe through. Their under-the-chin wraparound design also makes it harder for them to seal well over beards.

Thus we're pleased to introduce the best all-around mask we know of, the Elipse P100. This mask sits lightly on the face (total weight is under 5 ounces), seals well even over beards (though its 99.97% effective rating applies only to those whose faces are clean-shaven), and provides easy breathing for longterm comfort. Two adjustable elastic straps let the user ensure a good fit with minimal pressure on the head and face. Simple one-way valves direct exhalation through a port in the bottom of the mask, which keeps the filter dry and helps to avoid fogging your eyeglasses. The gasket material is made from a non-allergenic thermoplastic elastomer that is latex and silicone free.

This is an updated version of an article written by Zach Etheridge that appeared years ago in a print version of our Wood News customer newsletter.