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Thread: MERV 16 (or HEPA) Air Scrubber/ Filtration

  1. #1
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    MERV 16 (or HEPA) Air Scrubber/ Filtration

    Hi guys,

    I'm trying to improve the quality of the air in my shop. I've noticed that I get a sort of tightness in my chest just behind/below my sternum after a day of working in my shop. I have a plan for upgrading my dust collection, so now I'm turning my attention to air filtration.

    I have a Jet 1000B air filtration unit, but I now know that it's basically worthless for collecting the most harmful particles (less than 1 micron).

    I would like to make my own air filtration units, using two filters each (outer filter for the big stuff, inner filter for the fine stuff). I'd like for the inner filter to be MERV 16, which I understand to be as close to HEPA as I can get. My concern is that the finer filter will cut down air flow too much. My shop is about 450 SQFT with 8' ceilings. The floor plan is close to square, with no solid walls in the middle.

    So now, my questions... drum roll please.
    1. What kind of blower is recommended given my MERV 16 requirement and my shop size? Meaning, how much CFM, HP, etc do I need to overcome the filter resistance, without damaging the filter media?
    2. How many filtration units are adequate to create the proper circulation path for the air (I understand you want the air to move in a circle around the shop)?
    3. How much filter media surface area is recommended?
    4. What outer filter should I use? MERV 8 outer filter?


    Now let me preemptively rule some things out for you guys so that we can focus on the question at hand:


    • Yes, I know that the best method for reducing airborne dust is to collect it at the source.
    • Yes, I know that air filtration units are only a last resort, and that they can have a tendency to stir up existing dust. My goal is to collect dust at the source as much as humanly possible, and catch anything that escapes via my air filtration units, so that it doesn't have time to settle and be stirred up the next time I'm in the shop.
    • I also know that it can tend to pull new dust (as you're making it) up toward the ceiling and thus up in front of your mouth. To me, this comes down to being smart about where you position the inlets in the shop, and if necessary, wearing a respirator while performing those tasks. But I'm not going to turn the air filtration off during those tasks only to let the dust stay suspended in the air and later settle, only to be stirred up later. Seems like cutting off your nose to spite your face.
    • Yes, I have read Bill Pentz's website. I have a 3HP 4-bag dust collector, with integrated Thien baffles and two huge Wynn Environmental Poly-spun (or whatever they're called) filters. The thing still leaks a lot especially around the bag clamps... and emptying the plastic bags is not fun. So, I have ordered one of the Ebay cyclones (seller name is eastcaroga- nice guy), and plan to use my 3HP motor and impeller with it, and to vent outside.
      • Yes, I know, it will suck the heat outside- I'm willing to make the trade off
      • It's a stand-alone shop, so I don't have to worry about furnaces/etc
      • Yes, I know, I need a gazzillion HP motor and a giant impeller, to do it right but I'm trying to save some money by using the motor and impeller I already have.
      • Yes, I know the Pentz design will separate the dust better, but I'm not concerned about protecting the filter since I'll be venting outside
      • No, I don't have nearby neighbors

    • I have ordered a dust deputy and have a plan for redoing my shop vac setup to capture that dust- it's also a problem for me today
    • I have plumbed the shop with 6" ducting.
    • Yes, I have searched on this topic. There very well might be a thread I missed that answers this, so please feel free to include it here!


    Please, don't bring any of the above items up- I would really like us to focus on my question! I've read a lot of threads where people ask this kind of question, the thread gets overwhelmed with responses about the items above, and the question never ultimately gets answered.

    Thanks in advance!!

    Peter

  2. #2
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    Peter:

    I'm not sure why you are dismissing the Jet 1000B. I use it, and it dramatically reduces the particle count of 0.5 micron particles (if you can believe my Dylos particle counter). If a MERV 16 filter reduces its flow, wouldn't that just mean that it takes longer for every air exchange in the room (less per hour). Not optimal # of air exchanges per hour, perhaps, but still doing something.

    BTW, I have to check, but I think I have been using a MERV 15 outer filter on mine. I do have a 5HP Oneida cyclone, though, but no lack of airborne particles with belt sander or table saw.
    There is a very fine line between "hobby" and "mental illness."

  3. #3
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    I certainly can't argue with Dylos readings- I'm making the assumption that it's inadequate since it's rated only rated for 85% efficiency for 1 micron or larger. I have no idea what it does for particles smaller than 1 micron, but I assumed it was far less efficient in that range.

    But with a MERV 16 from what I read online, you can get 75% or better in the .3 to 1 micron range. With the ratings of the 1000B, it's probably in the range of MERV 12 or so.

    It's definitely better than not having one at all, but I was hoping I could do better than that with a home-built unit.

  4. #4
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    Not 100% sure what's around in the US now, and what the makers are claiming re. full HEPA filters - until recently at least it seemed like properly certified items were not readily available.

    Pressure drop won't be a problem provided you install enough filter area. Sizing/square footage will be determined by the rate of recirculation of air you decide you want - but that's a bit of a double edged sword by all accounts in that if you get into high enough airflows you may also (at least temporarily) raise a lot of dust in the workshop. Effective diffusion may be important. i.e. exhausting through a bag or something over a large area so that it wouldn't create draughts.

    The other issue though is that if too much fine dust is making it into the air (whatever about the effect on your lungs) because your at source dust collection system is not working very well the filters may blind up too quickly. i.e. effective at source collection is going to matter anyway.

    I don't think you're going to get anybody providing genuinely definitive information for a system along the lines you are thinking of - in that even if the work has been done, and even if an effective system can be achieved via this route it doesn't seem widely published or used. There may just be a reason for this....

    The other way of looking at it is that experience says that a high CFM Pentz style dust collection system seems to work pretty well as an air cleaner anyway - whether it does so by drawing in fresh air to replace that which has been exhausted, or recirculates it through a set of high quality filters. (they are easily set up so that both options are available by opening a blast gate) In a smaller workshop like i have anyway....

    If you're already on the DIY road to build some sort of super air cleaner, and already committed to reworking the dust collection system by buying a cyclone to drop out chips before exhuasting the rest, and are going to need/already have properly sized ducting to get effective at source collection then maybe there's no reason why you shouldn't alternatively and for similar input build a Pentz style system - it'd only require buying a 16in Clear Vue impeller and motor to suit... (the rest can be built DIY as i did)

    Which if true would bring it down to the question of which solution is likely to deliver the best results in terms of air quality and serviceability...

    ian
    Last edited by ian maybury; 04-24-2013 at 6:04 AM.

  5. #5
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    OK I know this is not exactly what you want so I'll apologize ahead of time, but some things to consider...

    First, it's impossible to collect all the dust at the source, even if you have brand spanking new top of the line Euro equipment there's still going to be dust that escapes, so your right about looking to improve your air filtration. I don't know the practicality of filtering out to sub 1 micron so I'll leave that to the engineers. In fact you may want to track down an HVAC forum to ask your specific question on matching motor/fan size to Merv rating and filter area?

    Second, if you feel your having some health issues related to dust now is the time to make changes before it gets worse. Optimizing your dust collection and air filtration are good steps. Another thing to think about is the types of wood you work with. If your one of those guys who loves working with exotics, you may have to reconsider. Exotics generally speaking are especially toxic for us to breathe and you'll probably want to avoid them. Other woods like cedars can also be irritating to the lungs. Many domestic hardwoods like maple, poplar, and oak are less irritating to work with.

    good luck,
    JeffD

  6. #6
    I bought a used Abatement Technologies Predator 600 air scrubber from my local Craigslist/Kijiji. It's used for containment in construction, is built like a tank, easily moved around, very quiet compared to my Steel City overhead filter I have at my cottage, has a HEPA filter and most importantly does an incredible job of reducing fine dust particles as measured by my Dylos.

    I was a little worried that it would be too small for my very small shop, but it does a good job.

  7. #7
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    I would buy a good face mask for sanding as that is when the fine dust will overpower the scrubber, and buy MERV 14 inner filters for the overhead. You are filtering the shop air every 4 minutes so the submicron stuff will be passing through quickly enough that even if the filter is only 33% efficient it will clean up the air in a few passes. All the other air you breathe won't be filtered as well as the shop. Dave

  8. #8
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    Thanks everyone for the replies.

    I have a P100 dust mask as well.

    I like the idea of diffusing the exhaust.

    I know that Merv 16 units exist, so maybe the best way for me to figure this out is to reverse engineer another unit.

  9. #9
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    Consider getting a Dylos .5/2.5 micron calibrated particle counter to get some empirically based information on what is working and what isn't .... perhaps have it in place after you do the cyclone/venting of the 'fines' outside and improving on the shop vac projects and before committing to the diy overhead dust filtration unit.......

    about generating an air flow/circulation pattern to better convey fine particles to an overhead air filtration unit..... as far as I've read in the woodworking forums (and what you have doubtlessly read) two units seems to be recommended..... but I don't see why, as a stop gap measure one of these units couldn't a cheap 20" square box fan (with or without filters) to help create that circulation pattern.... I've read about the use of 'smoke' sticks to visually confirm the existence of such circulation.....

    ....another thought..... add some merv 14 or 16 filter material behind the current filtering media of your Jet.... don't know how much this would affect output flow, etc. but with a Dylos counter you would be able to assess the effect of this (or other changes)

    good luck

    michael

  10. #10
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    Quote Originally Posted by michael osadchuk View Post
    Consider getting a Dylos .5/2.5 micron calibrated particle counter to get some empirically based information on what is working and what isn't .... perhaps have it in place after you do the cyclone/venting of the 'fines' outside and improving on the shop vac projects and before committing to the diy overhead dust filtration unit.......

    about generating an air flow/circulation pattern to better convey fine particles to an overhead air filtration unit..... as far as I've read in the woodworking forums (and what you have doubtlessly read) two units seems to be recommended..... but I don't see why, as a stop gap measure one of these units couldn't a cheap 20" square box fan (with or without filters) to help create that circulation pattern.... I've read about the use of 'smoke' sticks to visually confirm the existence of such circulation.....

    ....another thought..... add some merv 14 or 16 filter material behind the current filtering media of your Jet.... don't know how much this would affect output flow, etc. but with a Dylos counter you would be able to assess the effect of this (or other changes)

    good luck

    michael
    That's very sound advice. As an analyst by trade, your approach makes lots of sense! I'll see about ordering a dylos.

  11. #11
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    Hi Peter

    I enjoyed the specificity of your question. If I didn't already have four of the pictured units, I would build them.

    (first) I would go to my favorite filter supplier, and buy the largest, most common, best value MERV 16 filters they stocked. Then buy MERV 8 filters, and also some bulk filter material that I could custom cut myself.

    (second) I would source the largest, most common, best value, 'used' if I could find them, HVAC squirrel cage fans I could get.

    (third) Build an open-ended plywood box sized to hold the squirrel cage fan, and the generic (non-proprietary) filters stacked in each end of the box.

    (fourth) Mount them at the ceiling arranged to blow the air in a circular pattern.

    (fifth) Add an inexpensive ($10) wireless remote controller to each unit.

    filter.jpg

    I accept that I make a lot of dust that will never be captured by my cyclone dust extraction system. I too can feel 'consequences' after working all day in a less-than-perfect dust-free shop. And I know that sweeping raises all kinds of dust that cannot be seen. What I have described here is the best-value non-proprietary system I can imagine. Please share any improvements you can make.

    Lornie

  12. #12
    First thing I would do is get a particle counter, you may find that with the cyclone dumping outside you're circulating enough air through the shop you don't need anything else. With a 3HP DC in a fairly small shop you're going to be emptying all the air in 3600 cubic foot shop pretty darn frequently. As long as you are pulling 'clean' air in in such a way that you get decent circulation, you may very well not need anything else.

    That being said, if you still do need further filtration, you could probably get away with modifying the Jet to accept a higher quality two stage filtration system.

    Also, just saying Merv 16 doesn't really matter. The real question is what is the overall pressure drop of the filter(s) You can have a Merv 16 filter with a lower pressure drop than a Merv 14 filter. (for instance if the Merv16 has significantly more filter area). More filter area is almost always better (up to a point at least) but more filter area takes up more room and costs more.

    Merv 8 is typical of a pre-filter.

  13. #13
    Before I retired I was talking to some HVAC guys on the jobsite about shop air filtration. That's when I first learned about MERV and HEPA. Their recommendation was to start with a furnace rated squirrel-cage fan, since MERV 12 and over filters are often used with these fans. They then recommended as large a surface area I could create, given the dusty conditions, and placing a cheap filter in front of the HEPA filter. But static air pockets within the shop would not be affected by anything I built or bought so I would have to create an air flow within the shop that would ultimately direct the dust into the air filtration unit.

    By the time we were done talking about it, I realized that any thoughts of an air filtration unit keeping me from breathing in dust was a dream. While I'm standing there creating dust, by the time that dust made it to the ceiling mounted air filtration unit, I would have inhaled just as much dust as if the filtration unit wasn't there.

    A couple of months ago I took two box fans and built boxes on them on the intake side for (1) 5"x20"x20" MERV 13 filter and (1) 1"x20"x20" cheap filter. If I'm sanding at the workbench, I can place one fan blowing into the sander and one on the other side blowing away. Filtered air comes in across the workbench and pushes the dusty air into the second fan filter. I was surprised how much dust it captured, and I was using a Festool RO sander connected to a Festool dust vac.

    I take those fans and I place them where they do the most good, wherever the most dust is being spewed out. And when I'm done, I set them up to move air around the shop while I'm gone. When I return, it's as if I can smell the clean air. And the dust that used to make it into the rest of the house seems noticeably absent. Even with all this, I still wear a dust mask, because nothing is perfect.

  14. #14
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    Thanks again everyone for your responses.

    Lornie, ideally I'd do exactly as you've said. From some very light research, I'm finding it difficult to locate a squirrel cage blower with enough CFM at a reasonable price. At the prices I'm seeing, it would be just as expensive to buy a new air scrubber and take it apart. I haven't tried calling any furnace installer companies to see if they'd sell me any used ones, though.

    Jim, I think it does make sense to start with a dylos after I finish my cyclone setup, and then see what happens. As for modifying my existing unit (Jet 1000B), Wynn Environmental does sell better filters for them... but they only go to MERV 14. It's definitely better than nothing, and this might be because MERV 16 would be too restrictive. I might call Mr. Wynn to discuss.

    Julie, you raise good points. The concern that ceiling-mounted units will pull the dust past my face is fair. My plan for this is to position the exhaust of one of my ceiling units such that it blows across my assembly table. I'm thinking that I would use an exhaust duct that directs the air at a slight downward angle across the table where I do my sanding. To Jim's and Michael's points, it makes sense to start with my DC and shop vac upgrades, get a Dylos, and measure results. If I find that my .5 micron particle count reaches dangerous levels while sanding, then I'll need to come up with a solution. Your solution of using fans on either side of the workpiece makes a lot of sense- I would prefer to avoid dealing with that setup and the storage space required for the fans, but it might be worth the trade off to protect my lungs.

    What I don't want to do is turn the air scrubbers off while sanding. This would allow the fine particles to get suspended in the air, and perhaps settle in the shop, only to get stirred up and breathed in later. So if it came down to it, I'd rather wear my P100 respirator and run the air scrubbers while sanding. But I think the dylos would help take the guesswork out of the whole thing.

  15. #15
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    Bill Pentz has a plan for one. Looks simple to put together and cost is about the same as the jest with much larger filter area. I already bought the blower on ebay and I will be ordering the filter in the next few days. pm for detail if interested.

    http://billpentz.com/woodworking/cyc...ir_cleaner.cfm

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