Whole-shop Air Filtration Units Bad? [Archive] - Sawmill Creek Woodworking Community

Steve Aiken

05-02-2005, 2:55 PM

I was discussing the idea of making a whole-shop air filtration unit with the Oneida rep and engineer. They were very adamant that this was *not* a good idea. The following is an article forwarded to me in support of this argument....

Steve Aiken
Belleville, Ontario

Overhead Shop Air Cleaners Can Increase Airborne Health Hazards in the Woodshop

The ubiquitous air cleaners that hang on shop ceilings do not improve shop air quality. A scientific look at how they work and the percent of fine material actually filtered indicate that in the best case they do not improve shop air or in the worst-case scenario increase the fine airborne particulate in suspension. Recently a national wood working magazine published 3<SUP>rd</SUP> party filter efficiency tests of these units using a 1-100 micron test material dust. The results were misunderstood.

The test data actually presents a strong argument as to the ineffectiveness of these units. ASHRAE and other recognized tests use a test powder between 0.3 - 10 microns in size. The ASHRAE test measures the filter efficiency by measuring and counting all the particles that migrate through filter. It is the 1-10 micron particle size range industrial hygienists consider the most damaging to human health. This size has the ability to lodge into the deepest recesses of the lung, and is very difficult for the body to excrete. It is also the predominant size range floating for hours in your shop air. The test results indicate that even the best machine tested did not filter the finest and most lung-damaging material. If a one-micron particle is the size of a " BB" then a 100-micron is a bowling ball. The best filtering machine tested allowed 0.1 grams out of 80 grams through the filter. This might sound good on the surface but assuming a fairly even size distribution of the test dust (no size break down was given) the 0.1 grams represents the entire weight of all of the 1- 15-micron dust in the sample. Actually, calculating by average weights of the size distribution, it is possible that none of the material in the 1-15 micron range was filtered on the most efficient unit tested. It is precisely this range that constitutes the worst health hazard. A 100-micron particle, assuming stoke equivalent or roughly spherical, is one million times heavier than a one-micron particle, and has a settling velocity of about 10 inches a second, about the same as a falling cotton ball. Large particles this size are far too heavy to float up to the ceiling where the units are typically positioned.

Another misconception in the same article is the idea that the proper size air cleaner will filter all the air in your shop in 6 minutes. The example given: a 15 x 20 x 8 ft shop contains 2,400 cubic feet of air, divide this by 6 to get the minimum CFM required, which would be a 400 CFM air unit. Ventilation engineers use a factor for incomplete mixing which in this case would be a factor of somewhere between 7- 10. In other words, based on this formula the real length of time to filter all the air in the shop would be between 42 to 60 minutes, and this would only be valid if the offending external source of dust emission is shut down. Even assuming an ideal 100% filtration the removal process is much slower than the dust generation process. Meanwhile, you are in the shop breathing contaminated air.

Commonly woodworkers will comment, "when I look in the filter I see trapped dust, isn't it beneficial to collect at least some dust?" In this case the answer is no. Not with the machines tested here. The dust accumulated on the filter is only a fraction of the total dust drawn into the unit. The remaining dust is passed through the filter and exhausted. The circulating fan keeps this dust suspended and aloft in the air you are breathing. The dust on that filter is evidence that too much dust is in your shop air to begin with. Quoting American Governmental Industrial Hygienists, "When toxic contaminants are evolved in the workroom, recirculation must be avoided." This is why these units are not used in industry.

A properly designed dust collection system lowers airborne particulate to safer levels no higher than 5mg/M3. It does this by entraining the dust with air near the source of dust emission and then filtering the air to near 100%. Air quality testing in industry is performed routinely where workers wear dust monitors on their collar. It is not uncommon for well-designed dust collection systems to lower airborne dust levels by 10 to 30 times over uncontrolled environments. Get the facts and protect your health.

Sincerely,

Robert Witter

Oneida Air Systems Inc

Jim Becker

05-02-2005, 3:03 PM

I have always found this to be more of a mixed message. It is true that air filtration systems have limited or no value in improving air quality...you really do need to catch it at the source. But I also love my air filter for it's ability to help keep my shop a little cleaner from settling dust...you know, the stuff that doesn't get caught when you are hand-sanding or even spraying water-bourne finishes. It does bubkus for your health, but the layer of fines on those shelves is at least a little bit less. Mine also serves to circulate air around when I'm heating in the cold months for a more comfortable shop in a faster time frame.

Ken Salisbury

05-02-2005, 3:27 PM

Jeff Sudmeier

05-02-2005, 3:28 PM

I agree with Jim. When I am sanding, I still wear a filter mask. Also, I don't have any facts to back it up, but I used to use my sander with no vacuum attached and without the dust bag. (I know...I know!!). From the time I quit sanding until the time the air "looked" clean was about 5-6 minutes. Now this was sanding at the other side of the shop from the air filter.

I use my filter to keep my shop cleaner.

Bill Erskine

05-02-2005, 8:14 PM

... with an open blast gate to let it filter the air. While its a little ;) noisy, it certainly is moving lots of CFM and exhasting (Onieda certified) filtered air.

Dennis McDonaugh

05-02-2005, 8:39 PM

I've heard other people say the same thing about air filters and wondered why there would be less dust on everything if the air cleaner wasn't doing something. I guess the best bet would be to have it exhaust outside, that way the fine dust wouldn't be recirculated. BTW aren't 1 micron dust filters available for the air cleaners?

JayStPeter

05-02-2005, 10:05 PM

I always use mine when finishing. The amount of dust nibs at the end is definitely less. As already mentioned, the dust layer is also noticeably less after a day with the router or cutting up a bunch of MDF on the table saw.

Jay

Steve Cox

05-03-2005, 1:47 AM

When I first saw this it seemed to me that it was comparing the efficacy of a whole shop filter and a point source cyclone system. I would agree that a shop filter does not replace a cyclone but it just doesn't make sense that it wouldn't help along with a cyclone. Not everything can be hooked to my cyclone. This includes some sanders, routing operations, drill press, etc.

Jack Wood

05-03-2005, 7:25 AM

I too have read these writeup's from the DC companies and have gotten the impression that they are talking using air filters alone to take care of the dust problem. While it makes perfect sense that removing the dust at it's source is the best way to keep the dust down I also believe that one can't have enough of "all types" of dust removal. One of the themes that they keep repeating is how a ceiling mounted unit only gets what is at the upper levels and not at the floor level, that's why I use a large 220v whole house blower in a 25x25 box that sits on the floor using 3 normal filters as prefilters and a hepa type final filter. In the other corner of the shop is a ceiling mounted 16x20 filter using a 1750cfm attic fan, a regular filter and a filtrete final. I now have air movement at all levels of my shop and I use a 2 HP DC that vents to the outside of my shop. In addition if I'm cutting or sanding I wear a quality face mask (not one of those paper types). I have done all of this for around $500 bucks versus the $1500 to 3000 that one of the DC companies wanted to sell me for my 24x20 shop. DC companies are in the business to sell you DC systems and anything that will cut into that is going to be painted as "bad". So bottom line is you have to have a comprehensive plan to attack the dust threat, limiting your self to just one way or the other is short cutting your health.

Tom Jones III

05-03-2005, 8:34 AM

I read their point as the air filters are causing the fine particles to remain suspended in the air rather than just settle if you were not using anything. This implies that if you do not use their product than you are better off not using anything; clearly this also implies that using their competitors products is worse than doing nothing.

One flaw in their logic, even given that suspended dust is a bad thing, don't most people save the nastiest dust jobs for last then turn on the filter with a 4 hour timer then leave the shop?

Jim Dannels

05-03-2005, 9:25 AM

I had intended to built a ceiling mount filter.
But when I looked at the size of the salvaged Furnace Blower my brother-in-law gave me, It was large enough I could not figure out where to hang it out of the way (8ft ceiling).
So changed my plans and am now working on a downdraft sanding table/air filter.
My intent was to run it anytime I was doing any process that generated dust.
Is there some reason that would be a bad practice?

Michael Gabbay

05-03-2005, 10:32 AM

I would agree, this is a mixed message. I have a great deal of respect for Oneida. They produce high quality products and provide great customer service and advice. I have both a DC and AFS. I always run the DC when tools are on and run the AFS when I 'm doing fine dust emitting work like sanding or sawing. My feeling is every little bit counts. I always run the AFS for 2 hours after I leave the shop to clean things up and help reduce the amount of dust going to the rest of the house.

I think as long as you wear a NIOSH approved mask and use dust collection you are probably well protected. Also consider that most of us are hobbyest and only get in the shop a few hours a week.

My 2 cents....

Mike

Steve Aiken

05-03-2005, 11:05 AM

Good discussion and good points. I've read and re-read this article a good number of times. The article seems to be making three main points: (1) there were some problems with the magazine article; (2) even though it looks cleaner, the air may be harmful; and (3) Oneida cyclone DC are best.

I am put off by the initial dogmatism,
The ubiquitous air cleaners that hang on shop ceilings do not improve shop air quality. A scientific look at how they work and the percent of fine material actually filtered indicate that in the best case they do not improve shop air or in the worst-case scenario increase the fine airborne particulate in suspension. Personally, I'd like a little more detail on this "scientific look."

I've got to hunt down this mystery magazine article to better understand the context of this article. Does anyone know what magazine article they're talking about?

So, I've got a little more research to do on this.

Steve

It is an important point that we don't see the most dangerous of the dust. The biggest thing I got out of this article is the need to continue to use a respirator.

I'm still thinking about making a whole-shop filtration unit from an old HVAC blower. But I'm going to think a little longer before I start building. The Oneida rep and engineer recommended opening a couple of blastgates and running the DC for 15 to 20 minutes to clean the air. The advantage of this practice is that the air is filtered to 99.9% of all particles between 0.2 and 2.0 microns. The question I have about this method is 'how do I know that all the air in the shop gets filtered?'

The question I have about shop-made filtration units is 'how effective are the filters?' Many of the shop-made units I've seen use furnace filters. What are the specifications on these filters? Is there any independent testing done on them? Etc, etc. If you can find a filter medium that is a good as what Oneida uses in their DC systems, then how can a shop-made filter be bad?

Alan Mikkelsen

05-03-2005, 11:24 AM

First, I make every effort to collect dust at it's source. However, I have been operating a shop built (with a furnace blower) air filter system for several years. Everyone who walks into my shop comments on the lack of dust. My air filter system has four filters in it, in progressing orders of 'fineness'. I change outer two filters every other month or so, sometimes more often. My impression is that my unit moves a lot more air than most of the commercially available ones designed for home shops. It actually moves paper and tools on the wall behind it, from the circulation of the air in front of it. Without resorting to a hugely expensive scientific experiment, I'm a total believer in my dust system.

Jeff Sudmeier

05-03-2005, 11:33 AM

Onedia saying to leave blast gates open is ludicris! There you are just hoping that you are circulating air! If you set up a air filter with good filters, you will filter to the same amount you get with your cyclone.

I can kinda buy that they say particles are in suspension longer, okay the air is moving instead of still. However, them saying no don't use something designed as an air filter, use our cyclone to do it, just goes to show you the point of their article. (To sell more cyclones!)

Ken Waag

05-04-2005, 9:56 AM

The oneida points are good ones and should be taken into account. Hoewever, I think there are still advatages to air filtering. FWIW here are my thoughts on the issues.

Valid points for the Oneida statement:

Collect as much as you can at the source. The less dust that even hit the air the better.
A shop air filtration unit keeps dust suspended, so there's more to breath. True, and somtimes if you happen to be between the source ot the dust and the intake, it can actually be drawing all of this right past you. You may be filtering as much dust as the filration unit! (Except that you are of course wearing a mask)
Many commercial units filter larger particles and actually allow the finer (more dangerous stuff) through and recirculate it. So you can end up swirling the worst particles around and around. Incidentally don't rely on visibility. the stuff you nedd to woryy about, you can't see.
Turn over rate are innaccurate as you are not intaking equally from the whole shop. You are mostly grabbing the air near the intake. Points further will get there, but it takes time, so Oneida factoring is relavent and 40- 60 minutes is often more assurate than the 4-6 claimed.
Still I am a much in favor of air filtration. So the key may be to take those point into account and solve them in your filtration system:

Have intakes from as many points as possible. If buying or making the box type this may mean using two (2 small are better than one big) I read a good article which showed that one along each of opposing longer walls (assuming a rectangular shop) facing opposite directions creates a circle of air movement. Ideally they would be place 2/3 distans along the wall (intake toward the 2/3, output toward the 1/3). This kind of turns your shop into a bigger, slower version of a cyclone. The turnover is greatly improved as this little tornado forces particles to the outside where the filters are, so you get the dust to the filter pretty quick.

If you can build you own system; an old furnace fan (free) and ducting allow you to put intakes around the shop and one or more outputs. Now you're talking 6-8 min. turnover times.

The filters supplied are mediocre to keep the CFM numbers up. Again if you can build your own, just plan a good HEPA like filter into it. Upgrade filters on the commercial units to near HEPA levels.

Realize that air filtration systems are related more to Cleaning the Shop than Protecting your Lungs. I run my filtration system most often as I'm done working, and let it run (on a timer) for an hour or so after I leave. I come back to a nice clean shop with little if any dust settled on the floor, benches, and other surfaces. I will run it during esp. dusty operations like sanding, but I'm wearing a mask at the time too.

So I think that there are ways to solve the issues of air filtration and I find it a valuable addition to my shop, when done in this manner.

Remember no matter what else you do a good mask/respirator is the single best protection you can get ( and its the cheapest). I know its kind of a pain, but get a comfortable one and wear it as much as you can at least.

Jeff Sudmeier

05-04-2005, 10:35 AM

A shop air filtration unit keeps dust suspended, so there's more to breath. True, and somtimes if you happen to be between the source ot the dust and the intake, it can actually be drawing all of this right past you. You may be filtering as much dust as the filration unit! (Except that you are of course wearing a mask)

Ken,

You have a really well written post! I agree with it totally.

As far as standing between the dust and the filter, just don't do it. I know it sounds easy, it really is! They way that my filter is set up, it draws air away from where I do my standing if I am standing on the side of my sanding table away from the filter. If I stand between the table and the filter, the dust blows right by me.

So to stop that, I just stand on the side away from the filter and watch most of the dust float up and into the filter. (If the stuff I can see is getting up there, they stuff I can't is as well.). I have a hepa filter on my filter.

John Renzetti

05-04-2005, 11:15 AM

Hi, Little late getting in on this. I have to disagree with the Oneida article. While I try to get all the dust and chips at the source, there are times when I screw up like sand something without the vac on. Or just make a quick cut on a couple of pieces of mdf without turning on the DC. I have found that by turning on the shop filter, within an hour the air is definetly cleaner and clearer. I believe that these units have their place as part of a total dust collection system. Get as much as the source as possible and let the shop filter get as much of the rest.
take care,
John

Lee Schierer

05-04-2005, 12:46 PM

I was curious about this article so I did some checking. The filter on my Air filter unit (which is not Oneida) says it traps particles down to 0.5 microns. I just looked at a Woodtek unit in Woodworkers Supply catalog and it filters to 5 microns. They list another unit that doesn't have a brand identified that filters down to 0.5 microns. The have a Blueair unit that filters down to 0.1 micron. Delta says their unit Filters down to 1 micron. Seems like it gets all but the tiniest particles 0.5 down to 0.3 that the article mentions.

While having those small particles still floationg around may not be good for you. I'm definitely sure that having all the ones that you can see floating around isn't good for you. My air filter will run when ever I'm making dust in my shop.

As far as making your own, pay attention to the particle size removal rating of the filters or go with an electrostatic uit that gets them all.

Rob Blaustein

05-04-2005, 1:02 PM

How can it be bad to supplement a DC with a filtration system, if that system actually does filter out dangerous particles? Let's look at the JET AFS-1000B, for example--a fairly common hanging filter. On their website (http://www.wmhtoolgroup.com/index.cfm?area=shop&action=detail&iid=12918)they say that:

"Quietly cleans and filters the air in your shop while you work. Filtering 98% of all particles 5 microns in size and 85% of all particles 1 micron in size."

OK, so it's possible that these numbers are doctored. But I don't buy the argument that Oneida puts forth:

"...but assuming a fairly even size distribution of the test dust (no size break down was given) the 0.1 grams represents the entire weight of all of the 1- 15-micron dust in the sample. Actually, calculating by average weights of the size distribution, it is possible that none of the material in the 1-15 micron range was filtered on the most efficient unit tested."

It's silly to say that it's possible that none of the 1-15 micron-sized particles are filtered, based on the assumption of a uniform distribution and the weight of material recovered. I'd like to look at the article--the simple question is, in an independent test, how well do these filters work in filtering out particles in that size range. You'd have to measure the distribution of dust in the air without a filter, then in the presence of the filter. That should be do-able I think.

Greg Mann

05-04-2005, 1:12 PM

As far as making your own, pay attention to the particle size removal rating of the filters or go with an electrostatic uit that gets them all.

Lee,
You make a good point. If electrostatic filter make sense on a central air heating system it seems they would be effective for cleaning shop air as well.

I would like to hear from our good friend, Bob Marino, on this subject. While he may be a Festool ISA, he is also a respiratory therapist. Bob, as a Festool guy, you are focussed on source capture. But, as an RT, what do you think about ambient air quality in the shop? Everyone seems to understand the importance of source capture but what about the rest? Care to weigh in?

Greg

Steve Aiken

05-04-2005, 3:10 PM

I'm trying to keep an open mind on this topic. I don't currently have a filter, but will certainly build one if it makes sense. Good points all 'round.

Based on reports I've seen such as http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s189wood.pdf (http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s189wood.pdf) , it would appear that the most dangerous dust particles are in the 0.5 to 5.0 micron range for two reasons: (1) the human nose cannot filter them out, so they go directly into the lungs; and (2) they are so small they remain airborne for a very, very long time. In order for these filters to do more harm than good, they would have to filter out at least some of the particulate in the 0.5 to 5.0 micron size.
My observation is that there aren't alot of furnace filters out there that provide effective filtering of this size particle.

I found a document by the National Air Filtration Assn that describes filter testing at http://www.filtera-b2b.com/businessfilters/PDFfiles/NAFA_Filter_Guide.pdf (http://www.filtera-b2b.com/businessfilters/PDFfiles/NAFA_Filter_Guide.pdf) . Alot of this is Greek to me, but it seems that if a filter is tested under the ASHRAE Standard 52.2 and has a "Minimum Efficiency Reporting Value (MERV) of 13 it will remove 75% of particles between 0.3 and 1.0 micron on the first pass, and 90% of particles between 1.0 and 10.0 micron on the first pass. A MERV 16 filter will remove 95% of particles down to 0.3 micron. The problem is that I can't find any HVAC filters that are independently tested to meet a MERV 13 let alone a MERVE 16 .

The 3M Filtrete Ultra Allergen Reduction Filter has been tested to be a MERVE 12 filter. The 3M Tech Support people replied to my inquiry stating that this filter will capture "about 60% of particles between 0.2 and 2.0 micron in one pass.

I'm thinking that a shop-built unit using one or two coarse pre-filters along with a 3M Filtrete Ultra Allergen Reduction Filter should make an improvement in the quality of air in the shop. Of course, during dust producing operations primary dust protection should come from a NIOSH-N95 approved respirator, since it will take approx. 30 to 60 minutes for the volume of a small shop to pass through the filter unit two or more times.

A HEPA filter would be even better, but these seem to get very pricey, hard to find, and in awkward sizes. Another problem might be that because the HEPA filter is more restrictive, an HVAC blower might not obtain adequate airflow through the HVAC filter.

Of course, if you use the filter solely to reduce the dusting/ sweeping/ vacuuming, then I don't suppose any of this matters.

Steve

Bob Hovde

05-04-2005, 3:14 PM

Greg Mann

05-04-2005, 5:18 PM

Good points! The cleaner may not get the very fine, possibly cancer-causing dust, but the big stuff it catches would drive my allergies crazy! (And, I hate to clean the shop.)

Bob

I like my shop surfaces clean as well, but, in the process of taking out the bigger stuff, are we re-circulating the invisible stuff by constantly moving air without filtration adequate to get out the really harmful stuff? I'm not saying I know the answer, but I think that is the most important question here. When we say that it must be working because the shop is cleaner, we have met one goal. I don't think it necessarily follows that it is still healthier than letting the dust settle.

Greg

Rob Blaustein

05-04-2005, 5:47 PM

Here are two interesting web pages:

http://www.tinworks.com/tw/airfil1.htm
http://www.tinworks.com/tw/filtest1.htm

The second link re-iterates my critique of one of the conclusions reached in the Oneida article:

"However, it is open to criticism because weight measurements give predominantly the weight of the largest particles in the sample. This is generally true of filter test samples regardless of the absolute size of the largest particles. Little credit is given for the removal of very small particles because they contribute insignificantly to the total weight of the sample...

If all airborne particles were of uniform, filterable size, measuring filter efficiency by weight evaluation might prove satisfactory. Obviously, particles are not of uniform size."

DougButterfield

05-04-2005, 9:13 PM

I can tell you that the air in my shop can be clouded with dust and within minutes of turning on my air cleaner it is very noticeably cleaner.
If less particles are visable, it must be better air.

The source of the article is not identified - only the fact that Oneida is using it to promote their own products. So that makes me somewhat suspicious.

Like Jim said: "But I also love my air filter for it's ability to help keep my shop a little cleaner from settling dust...you know, the stuff that doesn't get caught when you are hand-sanding or even spraying water-bourne finishes."

Ken & Jim....I'm not picking on either of you...really. I'm using these two quotes as examples of a string of opinions running throughout this thread. Oneida, if I'm not mistaken, isn't talking about the dust that you or I can actually see. They are saying that the dust which we cannot see...the dust that is the harmful dust...is being recirculated throughout your shop when you run these cleaners. If I read their statements further, they say that if I use a system (presumably theirs) at the source, I can mostly eliminate the harmful dust, and the air filtration unit is not necessary for anything other than controlling the dust that I can see.

On the other hand, I could be completely wrong, and they're just pissed that they don't have the market cornered on filtration units. ;)

Jim Becker

05-04-2005, 9:21 PM

Doug, you make good observations. Oneida isn't "wrong" at all...they just are not acknowledging all the reasons one might use an air filter in the shop. I think that jives with what many folks are saying as you point out.

BTW, welcome to the Creek!!!!

George Matthews

05-04-2005, 9:48 PM

I'm trying to keep an open mind on this topic. I don't currently have a filter, but will certainly build one if it makes sense. Good points all 'round.

(snip)

The 3M Filtrete Ultra Allergen Reduction Filter has been tested to be a MERVE 12 filter. The 3M Tech Support people replied to my inquiry stating that this filter will capture "about 60% of particles between 0.2 and 2.0 micron in one pass.

I'm thinking that a shop-built unit using one or two coarse pre-filters along with a 3M Filtrete Ultra Allergen Reduction Filter should make an improvement in the quality of air in the shop. Of course, during dust producing operations primary dust protection should come from a NIOSH-N95 approved respirator, since it will take approx. 30 to 60 minutes for the volume of a small shop to pass through the filter unit two or more times.
(snip)

Steve

That is exactly as I have setup, and use in my shop.

The most frustrating part of the dust control plan was finding an effective and comfortable NIOSH-N95 approved respirator.

I found and use this (http://www.northsafety.com/usa/en/bs_product.html?GID=3721) mask from North.

There are seperate inlet and outlet valves in the mask. The lower exit valve diverts warm moisture from foging your safety glases. The mask is made from very compfortable silicone rubber, and I wear it for hours with little discomfort.

It is also very invepensive!

Earl Kelly

05-04-2005, 10:53 PM

I think alot of people have been pushed towards dust collectors and now cyclones with the findings of the posibility of wood dust being cancerous. I don't see how anyone could work without one of those today. But workers worked in non dust collection conditions for many, many yrs. How many know of someone with a sinus or lung cancer that worked in the wood industry. I myself know approx 20 people with over 30 yrs. working in that kind of situation, and none of them have had any cancer of that type.

Now don't get me wrong I'm not against dust collection. I have three units. But some of the micron sized particles people are talking about collecting are getting down to the size of spores and bacteria. The site below list the micron sizes of the various "bugs" we breathe every day.

http://www.thefiltermaninc.com/index_files/Page1364.htm

About the only thing smaller than some of the dust we're trying to catch is a Virus. I think if you can get down to 5 microns you're doing about as good as you can. But not even a downdraft table will catch all the dust from hand sanding, which is the single largest contributor to small particulate.

If you're really concerned about breathing dirty air, several respirators have HEPA pre filters available, can't get any better than that.

Ken Salisbury

05-05-2005, 6:11 AM

Ken & Jim....I'm not picking on either of you...really. I'm using these two quotes as examples of a string of opinions running throughout this thread. Oneida, if I'm not mistaken, isn't talking about the dust that you or I can actually see. They are saying that the dust which we cannot see...the dust that is the harmful dust...is being recirculated throughout your shop when you run these cleaners. If I read their statements further, they say that if I use a system (presumably theirs) at the source, I can mostly eliminate the harmful dust, and the air filtration unit is not necessary for anything other than controlling the dust that I can see.

On the other hand, I could be completely wrong, and they're just pissed that they don't have the market cornered on filtration units. ;)

Doug,

All I can say is when I run my air filter my breathing is noticeably better. I will let that be the judge as to the worth of the unit. :) :) :)

Steve Aiken

05-05-2005, 12:15 PM

Earl said,
I think alot of people have been pushed towards dust collectors and now cyclones with the findings of the posibility of wood dust being cancerous.

I would imagine the risk of nasal cancer to be relatively small. My primary reason for pursuing the clean-air-kick is that I have asthma which is triggered by wood dust. I am on a quest to make my time in the shop more enjoyable and asthma-symptom-free.

George said,
I found and use this (http://www.northsafety.com/usa/en/bs_product.html?GID=3721) mask from North.

Do you wear glasses, George? This might work for me if it rides low on the nose.

Steve

Kirk (KC) Constable

05-06-2005, 1:44 AM

I can tell you that the air in my shop can be clouded with dust and within minutes of turning on my air cleaner it is very noticeably cleaner....

I suspect that the air would be noticeably cleaner within minutes anyway...simply because the dust will settle.

I've considered an overhead unit, but always been skeptical of the claims. What I DO do is point the fan(s) so it blows past me and 'out' of the shop. That seems to help.

KC

Dev Emch

05-06-2005, 2:51 AM

I smell a rotten fish or a corporate herring. Here is why.

The article brings up an excellent point. The most dangerous dust is not the dust you can see. Those big jointer shavings and planer crunchies are not the item causing concern. Not even the fine dust that you wipe off of everything. Its the super small stuff that can stay airborne for a long long time. This is the stuff you can breath into your lungs and it doesnt leave with ease. Kinda like tobacco smoke.

Now, most dust collectors work on two premises not one. The first stage is to use a macho cyclone to kill off any kinetic energy that these large crunchies have and to drop them into a collection bin whatever that may be... garbage can, rotary air lock and open cannister, or sealed collection bin, etc. The bigger the crunchy, the loader the drop. The smaller the crunchy, the more apt it is to exist the cyclone unphased.

So now the air passing out of the cyclone contains lots of flour fine dust and tiny particles of that nature. It goes into the bag house or finishing filter unit. In regular designs, this dust actually builds up on the inside of the bag and improves the filter capacity of said bag. So its always good to have some dust inhabiting the inside fibers of the bag. In time, you shake these bags and this fine dust drops into the bucket attached to the bottom of the bag inside the bag house.

But how good are these bags and where does the bag exhust its air? In most cases, these bags recycle air within the shop. Shops in cold environments really wish to do this as its expensive to exhust the air to the outside. But if that air is being recycled and the bag house is exhusting back into the main shop, your doing the same thing that these hanging air cleaners are doing. Moving Air! How many full shop exchanges does your dust collector do per hour? So unless your installing a hepa filter on your bag house exhust port, it strikes me that this setup is doing the same thing. In actuality, it may be easier to install some form of super filter on one of these box units making them more effective than a full bore DC.

Now I do know that Onieda has some form of high performance polishing filter inside the central core of its cyclone. Most cyclones do not requiring the use of a bag house. I know that TIP tools offers some really high performance bag house filters for use with their sand blasting gear and they also sell an optional final filter for the bag house filter. It appears that super fine particles are getting through. So it sounds like no matter what you use, these super fine particles will be there to hunt us. Maybe we all need to buy one of those iconic breeze filters and make a guest appearance on The Sharper Image late night infomercials.

Ken Waag

05-06-2005, 7:32 AM

The problem is that I can't find any HVAC filters that are independently tested to meet a MERV 13 let alone a MERVE 16 .
Steve

Steve,
Good job on the research. I went through similar questions when I built my shop filtration system. And I had similar goals. No asthma but RAS (reactive airway syndrome) which basically means if I breath much dust I get congested like a bad cold. It gets to the point where the after effects, make you hesitate to go into the shop. So like you ,I aimed to make my shop enjoyable to use and to eliminate any after effects.

If you build your own you have more flexibility in filters and you can design it around non-standard sizes. You won't find much in the way of fliters rated above MERV 12 in the typical furnace sizes at H. depot and the like. If you try industrial suppliers (I'll use Grainger as an example) you can find several MERV 13 and 14. You don't have to worry about restricting the air flow as they are made with various capacities (CFM). They get expensive, but you can consider it a one time buy. Use lower rated prefilters so only the fine stuff gets to these and it takes a long time to fill them up. Many are washable.

Here are a couple of examples, but you can find plenty more with a bit of searching:
http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611769703&ccitem=

http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1613546978

Also realize that the first pass numbers actually improve with use as the dust that gets trapped actually helps to filter more and more dust (resistance does increase, so there comes a point where you need to clean them to maintain enough CFM)

I think getting above MERV 14 is pretty tough and expensive and true HEPA can be prohibitive. These are largely applied in hospital and clean-room situations.

I don't know your shop setting, but if you can think in terms of a whole shop system you can get far better result than a box. Your main cost is probably the filter. You can get a furnace blower 2000 to 4000 CFM and ducting free from a HVAC shop. The construction is similar in effort you just need a bigger box to house the fan and filter. If you do a box, do two. For 2x the job you'll get 8x the efficiency of circulation (rough estimates from an article). See my earlier post for reasoning. See the pictures below for an idea of my whole shop system.

I hope some of this helps in some way. Good luck in finding a solution that makes your shop enjoyable and healthy!

Boyd Gathwright

05-06-2005, 8:39 PM

Hi All,

.... Has anyone thought to ask Bill Pentz about this. He certainly has devoted a lot of time and done a tremendous amount of work in his life time on dust collection. I, for one, would be very much interested in his point of view, especially on this critical health subject. He is our only real expert here at the creek and I think perhaps he should be consulted ;).

Ref:http://cnets.net/~eclectic/woodworking/cyclone/CycloneReviews.cfm (http://cnets.net/~eclectic/woodworking/cyclone/CycloneReviews.cfm)

Boyd
.

Mike Stanton

05-06-2005, 11:42 PM

:D I have an 1100 dust collectoer with an home made cyclone+an jet 1000 air filter and I still wear a mask. Mike

Frank Pellow

05-07-2005, 8:21 AM

Thnaks for starting this post Steve and thanks to all those who have contributed.

I have a cyclone system but I don't (yet?) have a whole room filter. I am thinking of buting one, so am following this thread with lots of interest.

Steve Aiken

05-07-2005, 9:09 AM

Steve Cox

05-07-2005, 10:16 AM

Here is a link to the one section of Bill Pentz' web site that mentions air cleaners.

http://billpentz.com/woodworking/cyclone/Equipment.cfm#Filters

Simple gist is that they don't do much for your health while working but they do clean the air so the next time you go in the shop you don't have to deal with the dust from the last session.

Ken Waag

05-08-2005, 12:13 AM

Well thought out system you've got their, Ken, looks like it does a great job a recirculating every square inch of air in that shop. The only limitation is the quality of the air filter(s). What combination of filters do you use?

Steve

I got a roll of washable electrostatc filter material at HD and made my own pleated section to match my finer filter. Its MERV 10 and can be washed for a lifetime (I think it was $25). Then I have a V bank as per the link in my post above. Merv 14 very high efficiency and capacity. Listed there at $182, I got one while they were on "sale" for $120. Pricey, but it will take a long time to fill up and you can vacuum or blow it out, so it should last many years/lifetime.

The system works well. With the exhaust vents in the middle of the front wall and the intakes high along both side walls I get to circles that move pretty quick. I did a smoke test and cleared the space in 4 minutes.

Jeff Sudmeier

05-08-2005, 7:47 AM

Ken, thanks for the additional details on your post. You have the best air filtration unit I have seen in a home shop!

Ryan Higgins-Winter Haven

11-27-2017, 3:52 PM

Great thread. I WAS planning on buying a Baleigh Industrial air filtration system... then the shiupping cost on a $380 unit came out to $180... no thanks... I'll just die... but seriously- I am now thinking of a totally different method of attacking this issue.

Craig Hoehn

11-27-2017, 10:38 PM

I have to somewhat agree with Oneida, all of the commercial air shop cleaners are garbage and probably do more harm than good. They might keep dust nibs off your finish but they won't clean the ultra fine particles from the air. Nobody makes a woodworking shop air cleaner that actually works for the harmful stuff and if you try to build one out of an old furnace motor and filters from home depot it's really no different.

True HEPA filters are very fine and require a good amount of pressure to force air through them, as such a fan that is designed to deliver high pressure is necessary. There's really 3 main aspects that make a good filter unit, the fan, the filter, and air sealing the assembly. Its quite simple and yet all of these woodworking companies (JET, King, Steel City, Delta, etc) have it wrong.

The Fan:
If you are building your own filter and want to purchase a fan, the CFM alone means nothing, ignore it unless you have a fan curve. Looking at the fan curve, look at where it says "1" w.g." and read the air flow, that's the air flow you will get with a typical brand new HEPA filter. As the filter gets dirty the pressure drop across it goes up, usually the filter is changed when it gets to "2" w.g.", so read this off the fan curve and this will be the minimum flow. I have not been able to find a furnace fan that will go to this high of pressure and still have air flow, this is why you should look at a fan curve and know what you are getting before purchasing a fan. Note that this is just a rule of thumb starting point, the fan should be selected based on the filter pressure and capacity requried.

The Filter:
Look for true HEPA filters that filter 99.97%+ of particles under 0.3 microns. This is the gold standard for construction clean up, asbestos abatement, and most industrial applications, therefore i think this should also be applied to woodworking dust if you want the best protection. If you want to build your own, Camfil makes excellent HEPA filters.

The assembly:
The key to a good assembly, at least as far as performance is concerned, is getting a tight air seal around the filter. The filter itself needs to be designed with integral gaskets and the filter housing needs to compress this gasket to make a tight seal and ensure that there is zero air leakage going around the filter rather than through it.

A good air cleaner doesn't need to be complicated but using good quality filters and a proper fan isn't exactly cheap. Fortunately the asbestos abatement industry is doing it right and there are a lot of commercial air cleaners to choose from if you are looking for something off the shelf. I've dealt with Abatement Technologies and Novatek, both great to deal with so i would look into what they have to offer. I think having two of the PRED750's (from Abatement Technologies) or two of the Novair 700's (from Novatek) would be ideal for an average size shop. I don't have any affiliation with the mentioned companies, and there are more to choose from, I would encourage everyone to do their own research on the matter. It might even be better to call up a local asbestos abatement company to see what products they are using and there might be a company closer to home where its easier to get replacement filters.

Randy Heinemann

11-28-2017, 12:21 AM

I have never believed that there is a single answer to dust collection in the shop and, for many years, have used the following combination:

1. An Oneida cyclone for at source collection for my tablesaw, planer, jointer, bandsaw, router table and, most recently via a hood, my lathe (For the past 2 years it's been a cyclone with a HEPA filter.);
2. A HEPA filter vac for small power tools like sanders, handheld routers, sometimes the drill press;
3. A ceiling hung air cleaner which is on the entire time I'm in the shop and usually for at least 30 minutes after I leave the shop;
4. A powered dust mask which I wear when I am working for extended periods.

Since I upgraded my cyclone to an Oneida HEPA V Series, I do sometimes leave that running for awhile after using the tablesaw or bandsaw or router table and let it circulate air via the opened gate for my lathe hood. That cleans most of remaining dust out of the air quickly and the air cleaner can handle the rest.

I have read the articles indicating that air cleaners don't really improve air quality. I'm not convinced. At any rate, they certainly do remove dust from the air because there is very little settled on any flat surface in the shop. I have always thought that alone is an improvement because there is very little dust to be stirred up into the air when walking or using benches or tables.

I don't believe that any of the methods I use in and of themselves will do the job. Together, for me, it has worked.

Martin Wasner

11-28-2017, 12:36 AM

Twelve. Year. Old. Thread.

Frederick Skelly

11-28-2017, 6:37 AM

Twelve. Year. Old. Thread.

Yup. I think this is the oldest necro-thread that I've seen. :D :D :D

Rick Alexander

11-28-2017, 7:55 AM

Twelve. Year. Old. Thread.

Still relevant however. Just bought a Powermatic ambient air filter. I got fed up with seeing old sawdust collect on top of my dust collection pipes so I got a wild hair one day and took a bucket and soap to wash it off. Boy was I surprised to see that mold had formed on the sawdust over time. After cleaning the pipes I could actually tell a difference in my sinus irritation from working in the shop for longer periods of time. That settled it for me finally - after 12 years believing those overhead filters were useless I'm convinced preventing that buildup around my shop has benefits and if that filter system helps with that then it's worth it. I've got a cyclone, use about as good a setup to catch dust at the source, and collect all my sanding dust with a Festool setup but I still get dust in the shop. Maybe it's not perfect but I have no doubt it will help.

Steve Speiser

05-04-2018, 10:46 AM

70.Year.Old.Reader. Great Thread!

Roger Marty

05-04-2018, 12:55 PM

A Dylos Air Quality meter indicated to me that even my cheap $120 Wen air filter helps

Jerry Olexa

05-04-2018, 3:04 PM

My Jet air cleaner is effective for the ambient air that remains "floating" around as you are closing down shop for the day..I turn the timer on for 2-4 hours..When I come back the next morning, the air/dust is noticeably improved..Just my opinion

Patrick McCarthy

05-04-2018, 8:45 PM

Yes, an old thread BUT look at all the names of posters no longer here. Jim B and Lee S are moderators, but most of the others I hardly recall . . . and pretty sure in 12 years you won't remember me . . . maybe sooner.

Mike Heidrick

05-05-2018, 9:26 AM

Most of the proponents for no flters in the thread have left us in the last 12 years. ;)

Pretty cool idea though, blast gate off a second set of ductwok and put filter boxes at some y or tees. Wonder how fast I could filter my shed?

Timothy Shouldice

05-05-2018, 10:13 AM

A Dylos Air Quality meter indicated to me that even my cheap $120 Wen air filter helps

Exactly the same with me - even having a Wen air filter. The Dylos takes the FUD out of the equation. Turning on the air filter lowers the ambient small and large particle counts. Simple.

Randy Heinemann

05-05-2018, 10:20 AM

Exactly the same with me - even having a Wen air filter. The Dylos takes the FUD out of the equation. Turning on the air filter lowers the ambient small and large particle counts. Simple.

Very often I leave my cyclone dust collector on for awhile (sometimes 15 minutes or so) to ensure I have cleared all the dust out of the air. Since the dust collector itself moves close to a 1000 com and is equipped with a HEPA filter, there really isn't any dust to speak of left in the air at that point. I do also have a ceiling mounted air filter which I turn on when I start working in the shop and leave it running via a timer after I'm done for at least another half hour.

Scott Buehler

05-05-2018, 10:22 AM

Yes, old thread but interesting points on both sides, I'm planning on hanging an air filter along with my regular dust collection. Are the filters used in today's units, better that the units12 years ago?

Timothy Shouldice

05-05-2018, 11:19 AM

Very often I leave my cyclone dust collector on for awhile (sometimes 15 minutes or so) to ensure I have cleared all the dust out of the air. Since the dust collector itself moves close to a 1000 com and is equipped with a HEPA filter, there really isn't any dust to speak of left in the air at that point. I do also have a ceiling mounted air filter which I turn on when I start working in the shop and leave it running via a timer after I'm done for at least another half hour.

Very much what I do as well, if the Dylos is showing some operation put a lot of dust in the air, I'll run my main DC with an open gate. It really clears up the air. Basically I measure the dust levels and adjust as necessary - use a respirator, run the DC with an open gate, run the overhead air filter. Of course it all starts with a good DC system preventing as much airborne dust as possible. The rest is just measuring and managing the dust that still gets away.