Popular Woodworking 2001-06 № 122, страница 7
Circle #113 on Resource Directory Coupon arrow Letters continued from page 8 in building the table; spend an afternoon to protect your investment with the finish it deserves. Dust Collection Manufacturer Explains the Science of Microns After more than 10 years of perusing woodworking magazines I am always amazed at the unscientific conjecture in the letters and articles on dust collection. I see advertisements touting "5 micron bags" (as if this is a good thing) while not mentioning how much of the 5-micron material is actually filtered — 10 percent or less would be my guess. Industrial hygienists consider the health threat range to be mostly between 1 and 10 microns. The most common misunderstanding is that somehow it makes sense to blow dirty air out of a chip collector into the shop air and then try to pick it up with a piece of equipment that hangs on the ceiling. Forget that you are in the shop, breathing the air. It makes a lot more sense to put a good filter on the dust collector and stop the lung-damaging dust from entering your shop air in the first place. This is more cost-effective as well. I hear the argument that some material escapes the hood. Yes it does, but if the system is designed correctly, 99 percent of the fine dust is captured, on average, lowering the dust level by a factor of 5 to 20 times. Generally, 20 years of exposure with good dust collection is equivalent to one year without dust collection or bad dust collection. Bad dust collection can create more airborne respirable particulate than no dust collection at all. The object is to minimize exposure to the point where the health threat is eliminated. Proper dust collection is accomplished when dust is collected at the source and filtered to the smallest particle. Recently, scientists at The School of Public Health and Community Medicine at the University of Washington did a be-fore-and-after source dust collection study on a one-man wood shop. They found good source collection brought the dust level from an unhealthy, out-of-compliance condition to a level of three times cleaner than ACIH recommended levels. Get the facts. Protect your health. PW Robert Witter Oneida Air Systems Inc. Circle #116 on Resource Directory Coupon 10 Popular Woodworking June 2001 |
