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Filtering the Air in Your Shop
In "Getting Tough on Dust" we covered the first phase of woodshop dust collection: getting a handle on the large-particle dust, chips and shavings. But a dust collection system alone is not usually sufficient protection against fine wood dust. In reality, even the best dust collector can leave clouds of minute airborne dust particles floating through the air. Below, we'll look at the drawbacks of letting fine dust run wild, and strategies for handling the problem.
Dust Particle Size and and Respiratory Health
Dust particles are measured in microns, or thousandths of a millimeter. Larger dust particles - over 100 microns or so - are heavy enough to fall to the floor quickly. They're part of the mass of debris that collects with such alarming speed on the floor under and around your woodworking tools. Fine dust particles, on the other hand, don't have enough mass to be pulled quickly to the floor and can float through the air in your shop for a surprising length of time. Once a 5 micron wood dust particle is stirred up, it will stay aloft for 30 minutes or longer, depending on the air movement it encounters.
Dust particles under 10 microns constitute the primary respiratory health risk to woodworkers. They're easily stirred up, stay aloft for a long time, and worse, penetrate easily into the deepest reaches of the lungs, where they are reported to cause problems ranging from mild allergic reactions to severe and chronic respiratory ailments. While the seriousness of the health effects of long-term small particle fine wood dust exposure remains open to debate, more and more woodworkers, convinced by the evidence of health risks that currently exists, are beginning to take fine wood dust exposure seriously.
Improving the Filter Performance of Your Dust Collector
Dust collectors commonly used in small shop dust collection systems are sometimes called "chip collectors." That's because they are really designed to do their best work at collecting chips, shavings and large dust particles. Many dust collectors are equipped with a filter designed to stop only large particles, and let the fine particles associated with respiratory health problems pass through. Because dust collectors move substantial quantities of dust laden air, a dust collector that lets minute dust particles pass through its filter becomes, in effect, a "dust pump," filling the air around it with clouds of fine dust.
There are a couple of ways to prevent your dust collector from working against you in your war on fine dust. The simplest - and one of the most effective - is to locate the dust collector outside, or in a room that's separate from your shop and has its own ventilation system. For climates and shop layouts that make this solution impossible, the best alternative is to outfit the dust collector with a filter that traps fine dust particles.
For most dust collectors, a shaker felt filter bag offers a simple, affordable filter upgrade. Shaker felt is a fabric specially designed to trap small dust particles (down to one micron) without seriously impeding the air flow of the dust collection system. Of course, the best way to solve the "dust pump" problem is to buy a dust collector equipped with a fine particle filter in the first place.
Many dust collectors come standard with a filter that does a pretty good job with fine dust. Several dust collector models from Delta Tools comes with a filter bag that traps particles down to 1 micron. Other dust collectors are available with a "canister" filter consisting of a pleated fabric filter encased in a metal mesh container that fits on top of the dust collector. Jet and Powermatic offer a number of dust collectors with canister filters that catch dust in the 1 or 2 micron range. An added advantage of canister filters is that the pleated filter material greatly increases the air filtration surface area. The increased surface area means less air flow resistance and a longer time between filter cleanings.
Dust Collection for Handheld Tools
Handheld power tools - sanders, routers, circular saws, etc - pose special dust collection challenges. Many handheld power tools - even if they are equipped with dust collection port - don't lend themselves to being connected to a dust collector. Their small ports and cramped interior spaces aren't suited to the mechanics of a standard dust collector, which relies on its ability to move large volumes of air through the relatively large open spaces of ductwork and stationary tool interiors.
A shop vacuum is actually a much better choice for dust collection for many handheld tools. Shop vacs draw relatively small volumes of air, but unlike dust collectors, produce high levels of vacuum suitable for drawing small amounts of debris through the confines of narrow hose, small dust ports and the interior spaces of smaller tools.
Most handheld power tools that come equipped with dust ports can be simply "plugged right in" to one or another standard size of vacuum hose. There are also a few aftermarket solutions for tools not equipped with dust ports. The Edge Routing Dust Port, for example, fits most routers and does a great job of catching router chips and dust. The Whirlwind Dust Port is similar, but designed for use with Rockler's One Plate router base plate system.
Even an inexpensive shop vacuum can do a decent job of collecting dust from hand power tools, but remember to get one that either comes with, or can be fitted with a filter that catches fine dust. The quality of the filter in many shop vacuums is not easily discernable, unfortunately. It's best to look for a vacuum or filter that clearly states the particle size it will capture. Or, look for these letters: HEPA. They stand for "high efficiency particulate air," and apply to filters designed to catch 99.97 percent of particles 0.3 microns in diameter.
A step to a better vacuum is also worth considering. Fein Tools' Turbo series vacuums are designed to tackle dust collection from smaller tools. With vacuum power far exceeding most consumer shop vacs, much quieter motors, and fine particle filters (with an optional HEPA filter also available) a shop vacuum in this class can be a dream come true in the woodshop. Festool CT series vacuums are another great choice. Festool vacuums offer excellent dust collection power and efficiency, and - although they can be used with many other tools - are designed for use with Festool power tools as part of an integrated system.
Shop Air Filtration Systems
Even if you've done everything you can to improve your dust collection system's filtration performance, don't be surprised to find a coat of fine dust still settling on the surfaces in your shop. The fact is, much of the dust created in a woodshop never enters your dust collection system at all. In spite of your best efforts to set up an efficient, powerful dust collection system, some amount of the fine dust created by the tools it services will always escape into the air in your shop. Dust created buy hand-held sanders, for example, is among the finest dust created in the shop, and is also extremely difficult to completely capture.
Over time, the fine dust problem multiplies. The fine dust particles missed by your dust collection system remain in your shop, ready to be stirred into a dust cloud by the slightest movement of air; you'll add to the problem every time you use your shop. The answer is air filtration. An air filtration system picks up where your other dust collection efforts leave off by continuously scouring the air in your shop of tiny airborne dust particles.
Choosing an Air Filtration System
Like dust collectors, the performance of an air filtration system is measured by the volume of air the unit will move in cubic feet per minute (cfm). To be effective, an air filtration device should be rated to cycle through the entire volume of air in your shop 6 to 8 times per hour. The Jet AFS-1100B Air Filtration System, for example, has a maximum setting of 1044 cfm, which means that it will filter entire volume of air in a 20' X 20' shop more than 12 times per hour. Like most woodshop air filtration units, it has a built-in timer with settings for 2, 4 and 8 hours, making it a very convenient system to use - just flip the switch when you walk into your shop and forget about it.
A Healthier, More Enjoyable Woodworking Experience
Woodworking is a dusty business, and putting off doing something about it is surprisingly easy to do. But we encourage all woodworkers to start taking dust seriously. The investment in time and and money involved will be quickly repaid in a safer, healthier and more enjoyable woodshop experience.