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What  About  Conventional  Dust  Collectors?
How good are they, really?          What are their advantages and disadvantages?

Let's take a look at the conventional shop dust collector and examine its strengths and weaknesses from a perspective of effectiveness, cost, and practicality:

A Look at History:

Shop Dust Collectors
are Derived from the
Home Vacuum Cleaner

In 1907, a Canton, Ohio department-store janitor, James Murray Spangler, concluded that dust from the carpet sweeper he had been using was the cause of his chronic cough. He began experimenting, and created a machine to solve the problem by connecting an old fan motor to a broom handle and soap box with a pillow case as a bag to hold the dirt and dust. Further refinements led to a patent issued in 1908 and the formation of the Electric Suction Sweeper Company. An early unit was sold to Spangler's cousin whose husband, William H. Hoover, eventually became president of the Hoover Company where Spangler was employed as superindendent. After a period of sluggish sales and a series of product improvements, the company offered a 10-day free trial, and, as folks sometimes say, the rest is history. Hoover vacuums are still found on store shelves nearly 100 years later.

The Trouble with
Vacuum Cleaners:

Putting Fine Dust
in the Air

Conventional vacuum cleaners from the early 1900s until after the mid-20th century used that same basic principle found in the early Hoover machines: A fan motor sucks dirt and dust through a flexible hose, through the fan or blower, then into a paper or fabric bag that holds the dirt and acts as a filter with varying degrees of success. Most popular units still employed the same basic Hoover design until nearly 100 years later in the early 21st century!

The big problem with the Hoover design, which only a limited number of manufacturers have addressed effectively, is that dust-laden air is blown up into a bag, keeping the heavier dirt in a state of agitation, and causing most of the fine dust to remain airborne. The air and fine dust is then forced through the walls of the bag, where the dust is supposed to be retained in the bag walls and clean air returned to the room. However, if the bag's pores are small enough to capture the dust particles, they soon clog, causing the machine to lose suction. If they are made larger, the dust escapes into the room and ends up as a film of fine dust all over the furniture, increasing the need to continually dust furniture, books and bookshelves, ornaments and other surfaces.

Addressing the Bag
and Filter Problem:

Various manufacturers of household vacuum cleaners by the late mid-1900s began using assorted methods to reduce the amount of dust in the air by allowing the dirt to settle into a collection bin of some sort while air passed overhead, thus reducing filter loading. Eventually, this became the basis for various shop vacuums where a roll-around container with a blower on top sucked air through a hose into the container, then a filter was placed over the blower inlet to limit the fine dust re-entering the room atmosphere. However, the air volume moved by these machines was insufficient for effective control of dirt and dust around woodworking machines.

Soon a different kind of dust collector began to appear. It consisted of a blower with a larger hose inlet, similar to the old Hoover designs but on a larger scale, with a tube or duct, usually about four inches in diameter, carrying dust and debris to the blower, then from the blower into a bag or bin where the dirt and dust was deposited. There, the heavier material was allowed to settle, and the air, with fine dust still in suspension, was sent upward into an inverted bag where it was filtered to some degree as the air passed through the walls. Still the problem persisted, of pore size versus pressure loss as the pores plugged up with dust.

Over time, these units started injecting the air into the container at an angle from nearer the side of the container to create a swirling motion. Centrifugal force then accellerated the removal of some of the finer particulates from the air stream, reducing the load on the filter bag, but still the filter bag, being the last line of defense, was the weakest link in dust removal due to its inability to control the incoming dust load from the bin or dust container.



The major advantage of conventional dust collectors lies in one word: simplicity. They take relatively little room, a big issue in small and medium-size shops; and, in comparison with more elaborate and effective solutions, they are cheap. In a market where family finances dictates product choices, price often rules, and long-term health effects that come with the cheaper price are often sidelined or ignored completely as the user engages in illusions that he or she is immortal.

Part of product choice, especially where price dominates, is often the influence of consumer ignorance. Manufacturers and marketers of low-price equipment are loathe to reveal the weaknesses in their product. Busy consumers either don't bother to become informed, or they rely on various publications to "rate" various products. They then base their choices on those ratings or recommendations. In some cases, the publishers or writers of such articles fail to follow manufacturers directions (a troublingly common problem), or they may operate a machine outside of its intended or safe capacity (also not uncommon), or they sometimes commit other dangerous errors, with the unfortunate result that consumers are sometimes stuck with a poor choice and don't discover it until it is too late to return the product or avoid the purchase in the first place. Another danger is when consumers rely on the recommendations of friends who may have made a choice from an equally uninformed perspective.

The principle of caveat emptor definitely applies in dust collection. It is to your advantage to become well informed before buying a dust-collection system. The purpose of much of the information on this site is to provide you with the perspectives and knowledge that will help you make a better decision. We are not here to provide "cheap" solutions. We are here to provide environmentally safe solutions in an economically practicable, cost-effective manner. A few hundred bucks "saved" in an initial investment will seem very expensive if you find yourself suffering from asthma, cancer, or other respiratory problems with their attendant hospital stays and other, potentially very extensive, inconveniences or disabilities.



The biggest and dominant disadvantage of conventional dust collectors is a simple one: Conventional dust collectors do not properly address the problem of effectively separating the dust from the air before it gets to the filter. This leads to two other problems:

  • Too much fine dust is broadcast or "pumped" into the air, creating a major health risk, and

  • Shorter filter life if you try to use high-quality, effective fine-dust filtration.

These two problems, over a period of years, can make the low-cost, conventional dust collector a very poor choice, economically speaking.

Another problem with collectors with a hose connection directly into the blower is the danger of large objects, such as wood blocks or perhaps a tape measure, hitting the impeller and damaging or breaking it. This is sometimes addressed by adding a trash-can "cyclone" separator between the pickup and the blower to clear larger particles from the air stream. However, when any such accessories are added to the system, they also increase static pressure losses in the system, resulting in lower air flow and poorer dust collection at the tool.

a Better Way

The widely proven best way to control dust is a method that has been used successfully in industry and agriculture for years: the cyclone dust separator. Cyclones are hands-down the most effective, most practical path to clean shop air:

  • Centrifugal separation forces most of even the finest dust out of the air stream before it is passed to the blower and filters.

  • Properly designed cyclones have much lower static-pressure loss than other cyclones that were designed to sell at a cheap price. This means higher air volume, and much better dust separation and control.

  • Components selected for compatibility and overall system effectiveness produce much better results, resulting in lower operating and ownership costs.

Bottom Line:

It's Your Choice

Make it an
Informed Choice

When you consider a dust collector for your shop, look at the big picture. Certainly it is nice to look at a shop and see clean floors and clean tools. But it is even nicer to see no dust accumulating on shelves and other stuff in the shop, and it is marvelous when none of the dust finds its way from garage, if attached, into the rest of the home where it can affect other family members.

So what should you be looking for in a dust collection system? Try these ideas as a basis for comparison, in order of long-term health and economic importance:

  1. Does the system remove dust particles down to 0.5 (good) or 0.3 microns (best) from the air by using large-area, pleated filters that are certified by an independent testing laboratory, using industry-recognized methods, so you don't have to pin your hopes on the integrity of the supplier? A filter certified to remove 99.9% or more of particles to 0.5 or 0.3 microns (based on a maximum incoming particle size of 30 microns) is excellent. Keep air flow through the filter at under 5 feet per minute by using filters with adequate surface area (for example: a 300 square-foot filter for 1000 CFM produces an air-flow speed of 3-1/3 feet/second).

  2. Can the system maintain at least 4000 feet/minute through ducting where air is carried vertically upward? Maintain at least 3000 feet/minute in horizontal runs (6-inch pipe at 1000 CFM moves air at 5000 feet/minute).

  3. Does the supplier recommend at least 6-inch ducting diameter from tool to collector for acceptable static-pressure drop? 4-inch hoses are of little practical value in most serious shops (even small ones) where you are using a 10" table saw, sanders, jointers, planers, etc.

  4. Are there adequate hoods around tools to collect an envelope of air around the tool so fine dust cannot escape? In some situations, the hood may be unable to capture larger particles flying from the tool at high velocity (such as chips or slivers coming from a piece of hardwood being cut on a table saw), but those can be swept or vacuumed up. The real target here is fine dust.

  5. Does the system use a high-efficiency, cyclone or centrifugal dust separator of proven performance to remove well over 99% of the dust from the air, including much of the micro-fine dust, so that the filters do not have to carry the bulk of the responsibility for dust removal? This keeps the air clean and greatly reduces the cost of buying and replacing overloaded filter media. It also eliminates the need for bags with coarse pores that allow dust to be pumped into the air, thereby increasing health risks.

There are other considerations as well, but a system that meets these requirements will generally provide good results in keeping the shop air clean, and in the process, it will also keep the shop floor, tools, shelves, and everything else much cleaner than with other methods.

Be Wise

Be Careful

It's Your Health

It's Your Life

We all have purchased a power tool and found a laundry list of warnings about the dangers associated with the tool. Admonitions like, "Do not operate without shields and guards in place," or "Do not use in damp or wet locations," and the like. But rarely do they include warnings that say, "Do not use without proper dust collection equipment."

Yet, asthma and cancer can be just as debilitating and just as life-changing and life-threatening as cutting one's finger off on a table saw, or grinding it into hamburger on a jointer without proper safety guards in place. Far too many woodworkers and others work in dusty environments with little regard for the dangers they are exposing themselves to by breathing dust-laden air -- especially the large amount of extremely fine dust coming from cutting or working with MDF or other products containing wheat straw, unknown glues and bonding agents, and other hazards.

A well-designed, properly equipped, and properly installed dust collection system that cleans up the air as well as your shop is your best defense and best insurance against acquiring serious health conditions as a result of your woodworking or other shop activities and experiences.

You have the power to choose. Choose wisely. Don't expose yourself to unnecessary and completely avoidable risks by ignoring the experience of the numerous woodworkers and shop workers whose damaged health has robbed them of the fulfilling satisfaction of being able to make things in their own shop! Saving a few bucks in the face of these kinds of consequences simply is not worth it.

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Updated May 26, 2004

©Copyright 2004, Clarke F. Echols and Clean Shop Air, LLC. All rights reserved.
No part of this material may be copied, reproduced, or redistributed in any form
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