ARTICLES & REVIEWS

Introduction

Sadly, I take severe exception to the recent American Woodworker article by Dave Munkittrick (AW #100, May 2003). Overall it is a good article and shares many useful suggestions, but the homework was not done properly before it was published. This is strictly a dust collection article in the traditional sense, meaning it is geared to pick up the same sawdust that you can get with a broom. It will do that job well. What that article will not do is help you to amply protect your health.

I learned the hard way that this whole wood dust issue is serious business. I became pretty motivated when my doctor took away my tools and I was left on an oxygen hose. Frankly, I could buy a new Felder combination machine every few months for what my insurance company and I currently spend on my medical care. I've dedicated much of my free time for the last three years trying to help educate myself and fellow woodworkers on the hazards of wood dust, and to engineer affordable protections. If you are uncomfortable with my information, please take the time to look over what the experts say. I would suggest starting with OSHA on Wood Dust and going from there look at my Links Page.

The Risks

My doctor, a fellow woodworker and pulmonary specialist said the under 30-micron size particles (about 1/3 the thickness of a human hair and smaller) that go right through our filters pose the worst health hazard. He explained these fine particles also slip right past our body's natural defenses to lodge deeply in our tissues. Our bodies have a difficult time getting rid of this dust. Moreover, trees over millions of years have built up chemical protections. Like smoking, some will never show symptoms, but continued long-term exposure to fine wood dust and these chemicals results in most woodworkers, their families, and others close to them developing sensitivities. A few develop more serious sinus and respiratory problems including asthma, emphysema, allergic reactions, polyps and even cancer as reported by the National Institute of Health News Release. (Be patient; it takes a long time for this PDF file to load.)

Hand sanding and machining produce these fine particles that you can see in a beam of sunlight. When my doctor took away my tools, he explained most of our tools and most of the dust protections we buy, including our dust collectors, air cleaners, down draft tables, and even shop vacuums are little more than dust pumps because of poor design and filters that are far too open. Our tools spew fine dust everywhere. This fine dust is so small and light that once airborne it quickly spreads uniformly polluting the air in our shops and all connected areas staying airborne for hours. He told me that wearing our dust masks helps but I took it off long before the four to six hours it takes my fairly high-powered air filter (rated at 8 full air changes for my shop an hour) to clear that fine, most harmful dust. Worse, that fine dust comes home with us on our clothes to also expose those close to us.

Commercial Solution

So many professional woodworkers had respiratory problems that federal air quality standards went into place over ten years ago. An Australian health regulatory agency summarized the extent of this problem by saying wood related respiratory problems disable and force one in every fourteen professional woodworkers into retirement. Woodworker unions still complain these new standards are still too lax because too many workers are still having respiratory problems. Meeting these new standards required commercial woodworking concerns to redo their dust collection from what we still use as hobbyists standards. The old standard went from capturing the dust after the fact in an air cleaner, to requiring capture of the fine dust at the source. Once captured, the new standard requires either exhausting the air outside, or ample filtering to remove the fine, most dangerous particles.

Hobbyist Solution

These government standards are well and fine for professional woodworking concerns, but there are no equivalent requirements for hobbyists, and most hobbyists would not care for government intervention anyway. As a result, although hobbyists work with wood less often, they regularly expose themselves to fine wood dust concentrations hundreds to thousands of times more dense than permitted commercial standards.

I personally made a nice air cleaner and used "fine filter bags" thinking I was taking excellent care of myself, but my doctor still took my tools away. That could not happen to me! I have three engineering degrees with 35 years professional experience and 29 years of part-time teaching university engineering at UC and CSU and was always careful. Although my doctor was far more kind, the bottom line was my arrogance and lack of real information took away my tools and landed me on an oxygen hose.

My choices came down to giving up woodworking or find a solution. Although my efforts have touched everyone who uses a PC or gets put on a hospital critical care monitor, most of my work is so far removed that I rarely even see the results. As one who really likes to build tangible things that others can appreciate, woodworking has long been one of my favorite hobbies. Not willing to give up that enjoyment, nor my lifetime accumulation of tools that friends with professional shops drool over, I got serious with my research. What I quickly discovered is there are no hobbyist standards, much of the vendor information can not be trusted, and most woodworkers, myself included, do not know much of anything about what it really takes to protect themselves and those close to them from fine wood dust.

Research

My research quickly verified my doctor's comment that hobbyist dust collection is a mess! Our tools are mostly poorly designed in terms of good fine dust collection and send the fine most dangerous dust everywhere. My hobbyist dust collector and many other of the most popular brands provided no where near the advertising claims for horsepower, CFM, and filtering. Moreover, most of the standard 4" diameter hobbyist industry ducting that we buy, provides poor efficiency and fails to move enough air.

Low cost Pacific Rim import copies of older tools pushed hobbyist woodworking tool manufacturing off shore. Even then, enough direct sales firms market these copied "tools by the pound" to make the competition for entry-level hobbyist business beyond fierce. To stay competitive many firms engage in an ugly advertising war. Unfortunately, our truth in advertising laws let a vendor claim anything they can demonstrate. With the appropriate "tricks" and testing, unscrupulous vendors bombard hobbyists with useless performance claims. Credible vendors find themselves forced to either similarly compete or watch their market share rapidly decline in favor of supposedly better performing lower cost products. Here are a few of the techniques that vendors use to make their outrageous claims.

1. Blowers configured with special hyperbolic inlets and with no filters or ducting move just about double the air that they move under real working conditions.
2. Motors, when starting draw far more than their working amperage; converting that start-up power into horsepower makes for ridiculous claims.
3. Filters can simply build up enough dust cake to sustain any level of filtering claimed as long as they don't also have to pass any air. The key is never say what airflow comes with that level of filtering.
4. Ducting mostly comes in 4" diameter sizes with sharp ninety degree bends, Ts, and very rough walled flexible hose. This stuff kept my shop floor clean and the fancy metal stuff I bought really made my shop look professional, but it failed to capture most of the fine dust.

Informed Decision

With no real hobbyist standards to turn to, I went to the professionals to make an informed decision on what I really needed.

CFM

They recommended American Air Filter (AAF) as one of the most respected names in industrial air quality. AAF produces the standards that many air engineers use to design commercial systems to meet current Federal air quality minimums. The AAF tables ensure capturing the fine dust at the source and require either exhausting the air outside or filtering ample to remove the most dangerous particles. Chris O'Connor, a manager with AAF was kind enough to let me use their information to produce the following table

These huge CFM numbers made no sense to me at all because I know the fine particles take the least air to move! It was not until trying a simple test that I understood why we needed to move so much air. You can verify this yourself with a simple experiment. Get a couple of soda straws and a balloon filled with air. You suck and let a six-year old blow (substitutions allowed but the older they get the more they enjoy beating you). See who can control the movement of that balloon. With at least double the lung capacity, you have zero chance of maintaining control. The reason is sucking pulls air in from roughly all directions while blowing sends a directed stream of air. Unless you take in a big enough bite or sphere of air, that balloon is going to be moved by any air current. The same occurs with the fine dust that we make from hand sanding and machining. Almost any air blowing from blades, bits, cutters, belts, motor fans, etc. moves that fine dust quickly away from the tool. Once it escapes the immediate area of the dust hood, it quickly spreads to fill the air in your shop and any connected areas such as your home. Moreover, our tools, fans, blowers, etc. will keep it airborne.

Resistance

Moving 800 CFM at your machines requires overcoming the considerable resistance from ducting, filters, hoods, and separators (calculate the resistance in your shop using the static calculator on my site).

Blower

The computed static pressure resistance for your shop combined with the AAF airflow requirements table for your larger machines (800 CFM for most hobbyists) will let you use a good fan table to quickly decide how much blower is needed for your shop.

Blower Purchase

Knowing what we need and matching that with a real product can be quite a challenge without knowing a couple of key details. First, you have to have a large enough diameter impeller. If the impeller offered is not at least as large as the impeller required for your needs as determined by the above fan table, that blower will not work for you.

Second, you have to have enough motor to turn that sized impeller when working in your system. Maximum amps are obtained with maximum airflow. Use the above fan table to look at the horsepower requirements for a blower ample for your shop at maximum airflow. The National Electric Code, table 430-148, lists the following amp draw for electric motors at 240 and 120 volts.

• 1.0 HP = 8/16A
• 1.5HP = 10/20A
• 2.0 HP = 12/24A
• 3.0 HP = 17A/120V is not available

Filter Purchase

I bought a set of dust collector bags advertised by a major hobbyist vendor as better than 1-micron. They still left my shop dirty with fine dust coating all and not long after starting their use, they had turned an ugly color of brown. I called the vendor displeased and was told I had to build up an ample cake of dust on these bags for them work properly. After nearly a year of use, that cake should have been ample, but instead my shop continued to be coated in fine dust. While using those bags an asthma attack took away my tools. My research and testing my bags over at the university showed they freely passed up to 30-micron sized particles all day long until so clogged with dust they would not pass air. I complained to a fellow woodworker who also teaches university engineering and is far more involved in the testing of this type of equipment. His tests showed my tests were optimistic. Many of the popular fine filtering bags pass up to 50-micron particles. His recommendation was to shift over to cartridge filters that have been independently tested by an American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) certified testing lab.

Cyclone Purchase

Thinking I finally had it all figured out, I planned on buying a cyclone with fine cartridge filters and replacing all my existing ducting. Just to make a final check before I sent in that rather expensive order to a single firm to have it sent right away, I ran my list by a good friend and fellow engineer who already owned the same system I intended to buy. He is one of those people who will never say a disparaging word about anyone. Instead of his blessing he said no to my plan and told me to go do more homework. I did and discovered the cyclone I planned on buying leaked badly, stopped up whenever used for heavy planing operations, was inappropriately sized for my shop, and would collapse with the blower and motor I selected.

Frankly, that was pretty much the last straw and made me angry. With months off work and little else to do, I filled my time documenting what I learned in my cyclone and dust collection research web pages. I also took the time to engineer a good quality and very efficient cyclone and blower combination that I built for less than the cost of a typical 2 hp dust collector. These sites document much of what I learned and the detailed steps I followed to make my shop safe from fine dust

Ducting

Poor ducting design will preclude a big enough blower from providing ample airflow for good collection at each machine. We need enough CFM at each machine to capture the fine dust at the source. Air, just like water, is significantly restrained by the size of the pipe it flows through. Pressures from typical hobbyist dust collectors will move about 400 CFM through a 4" diameter pipe, 600 CFM through a 5" pipe, and over 800 CFM in 6" pipe. I was not particularly happy to find my many hundreds of dollars of custom designed 4" diameter ducting left my blower choked. My choices were to miss much of the fine dust, step up to a roughly 7.5 hp unit with a huge impeller, or redo my ducting to all 6" pipe going to each of my larger tools. Because air will compress around a small obstruction, I went with all 6" diameter pipe and flexible hose using a tapered 6" to 4" adapter right at each of my larger machine to not lose too much CFM. I just could not bear cutting the cabinets of my pretty machines open.

Yes, 4" and sometimes even 2.5" pipe works fine for many, but that sized pipe does not move the volumes proven as needed to consistently pick up the fine dust. All with 1.5 hp blowers and larger who make the upgrade to 6" ducting find an incredible positive difference in how much better their systems work, and most wonder why that is not already an industry standard.

Terry Hatfield suffered continuing dust problems that affected his and his daughter's respiratory health. He bought a Grizzly 1029 2 hp dust collector. It helped keep the floor clean but all continued to be covered in fine dust. Terry had watched from a distance some of the flame wars and other dust collection controversy on the different woodworking forums. That led him to my web pages early on, but he felt my approach too extreme. Still coughing and wheezing, Terry followed the advice of other woodworkers. He bought a set of supposedly fine filter bags to replace the originals on his Grizzly. Those bags worked a little, but not well enough that he and his daughter were able to overcome their symptoms that made woodworking unpleasant. Figuring they enjoyed woodworking too much and had way too much invested to quit, Terry reluctantly tried my recommendation to upgrade his shop with 6" duct. The results worked so well he put larger adapters on his machines. Seeing the fine dust went right through those so-called fine dust bags, he followed my plans to build a cyclone and added a fine Farr filter. Terry was pretty excited that my design allowed him to build a really top of the line dust collection system for about the same cost as a good dust collector. He could not believe how much cleaner it made his shop (click here for his shop tour) that shows his ducting, cyclone, and filter.

Terry joins many hundreds of other very pleased woodworkers who have now done the same, but Terry went one step further. With a friend in the sheet metal business, Terry decided to try to help fellow hobbyists by making my design available as inexpensive metal cyclone and blower kits (see Dust Eliminator - click here for details). Although I declined to become his partner, I have continued to help, plus asked a number of my woodworking friends all over the country to build prototypes. Those units are just now getting finished up and the early reports are nothing short of incredible. Moreover, as part of the agreement to get one of those test units, each provided feedback and suggestions as to how to make the building go smoother and easier. The result significantly upgraded my plans and detail for construction, plus left Terry with a far superior kit. That cyclone has the least resistance of any unit available for hobbyists and some of the best filtering, plus moves more air than any other 3 hp or smaller cyclone available. Moreover, it pushed me into refining my blower designs to make them far easier to build and much more efficient.

^© 2003 by Bill Pentz . All rights reserved.
No parts of this article may be reproduced in any form or by any means
without the written permission of the publisher and the author.