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Thread: Whole-shop Air Filtration Units Bad?

  1. #16
    Join Date
    Sep 2004
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    St. Louis
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    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:

    1. Collect as much as you can at the source. The less dust that even hit the air the better.
    2. 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)
    3. 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.
    4. 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.
    Ken Waag

  2. #17
    Quote Originally Posted by Ken Waag
    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.
    Jeff Sudmeier

    "It's not the quality of the tool being used, it's the skills of the craftsman using the tool that really matter. Unfortunately, I don't have high quality in either"

  3. #18
    Join Date
    Feb 2003
    Location
    Chadds Ford, PA
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    583
    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

  4. #19
    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.
    Lee Schierer - McKean, PA

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Contribute

  5. #20

    huh?

    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 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.

  6. #21
    Join Date
    May 2004
    Location
    Oakland, MI
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    492
    Quote Originally Posted by Lee Schierer

    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

  7. #22
    Join Date
    Mar 2005
    Location
    Ontario, Canada
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    115
    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 , 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 . 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

  8. #23
    Quote Originally Posted by Ken Salisbury
    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."
    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
    Spinning is good on a lathe, not good in a Miata.

  9. #24
    Join Date
    May 2004
    Location
    Oakland, MI
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    Quote Originally Posted by Bob Hovde
    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

  10. #25
    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."

  11. #26
    Join Date
    May 2005
    Location
    Cleveland, OH
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    14
    Quote Originally Posted by Ken Salisbury
    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.

  12. #27
    Join Date
    Mar 2003
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    SE PA - Central Bucks County
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    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!!!!
    --

    The most expensive tool is the one you buy "cheaply" and often...

  13. #28

    NIOSH filter

    Quote Originally Posted by Steve Aiken
    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 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!

  14. #29
    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.

  15. #30
    Join Date
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    Quote Originally Posted by DougButterfield
    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.
    "If you believe in yourself and have dedication and pride - and never quit, you'll be a winner. The price of victory is high - but so are the rewards" - - Coach Paul "Bear" Bryant
    Ken Salisbury Passed away on May 1st, 2008 and will forever be in our hearts.

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