# Air Filtration!



## jaysonic (Jul 14, 2012)

So, I've recently discovered that I'm allergic to all wood airborne particles. What a downer. I've been working in my shop with a real skookum dust mask for the last few months, but I've decided I want something more. I'm getting an electrician to re-wire my shop so that I don't blow breakers when using two tools on one outlet, like a shop vac and TS. I also have a wonderful blower, really loud, but boy does it move air. I've noticed that with this blower on, I don't even need a dust mask to avoid the allergic reaction, although I still wear it when doing tasks that really put out dust. However, I now really want to BUILD an air filter. This way,with the combination of, shop vac hooked up to my tools, dust mask, and blower, I can now have an air filter that runs while I'm working, as well as afterwards to really help keep it cleaner. NOW: to my question:

I've been reading a lot on air filtration systems, but I thought I'd ask fellow LJ's their advice. What is the best way to construct one? My sisters boyfriend is an HVAC man, and he's now started looking out for a fan for me. Would a furnace fan work best? How many filters do I use? Pre-filter, post-filter? Rubber gasket seals? I'd like to hear anything and everything from anyone and everyone, haha. Maybe even a little help on the design itself.

I've never made an air filter, and, since I'm allergic to wood…I don't want to have to do this more than once, I want it to work right the first time. So, thanks in advance for all your help!!

Jason


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## SSG (Sep 11, 2012)

They discuss this issue in a very old issue of Wood magazine, they built a box out of plywood and use a squirrel cage blower. If you use a pre filter with a Merv 13 filter it would work best. I just moved I will have to look for the thing and get back to you.


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## nwbusa (Feb 21, 2012)

You used "skookum" in your post and have therefore been positively identified as Canadian


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## jaysonic (Jul 14, 2012)

Wow, thanks SSG, that would be really helpful.

Haha, thanks John. Van. Isl, BC.


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## Grandpa (Jan 28, 2011)

I think if you use a squirrel cage style fan you will want the filtration on the suction side. I personally would look into some of the filters used on commercial units then use a prefilter that you buy locally off like a furnace filter. The second filter is the one that will collect the fine particles and those are the bad guys. The primary filter will keep the secondary filters cleaner. Those filters should collect the very finest particles. Look at some web sites of different companies and see what you find. If you use a fan then you usually put the filters on the discharge side of the fan.


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## OnlyJustME (Nov 22, 2011)

You can watch this guys youtube videos
I made one using a multi-speed air handler/furnace fan to create a negative air pressure during a kitchen remodel so dust didnt get all over the house and it really moved a lot of air. Enough to keep pulling down the plastic sheeting on the doorways. It sat on the floor and resembled one of those used for mold or asbestos removal and i just ported it out the back kitchen door. I made it out of 3/4 plywood and used caulking on all the joints before i screwed it together so there weren't any air leaks. Made it the same size filter as my old delta shop filter but it definitely out performs the delta. I did a double filter on it using a mid grade filter from the big box store and a filter i ordered online with a .1 micron rating behind it. Merv 13 i think as SSG stated. funny how all the filters sold at HD or lowes have their own rating systems so that you cant really compare them to others. none of them had any merv rating on them that i could find. 
Good luck


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## DIYaholic (Jan 28, 2011)

My air cleaner will use 3 filters. Two pre-filters (16" x 20" x 1") on the intake, one ultra cheapo to catch really big stuff, then a MERV 9 for smallish particles. I will then have a MERV 11 (16" x 20" x 4") on the exhaust, to filter out the itty bitty nasty microscopic stuff. My squirrel cage is wired to a variable speed control & a 12 hour timer. Grainger was supposed to call me today when my MERV 11 filter arrived. Maybe they will call tomorrow…...


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## jaysonic (Jul 14, 2012)

Is there a benefit to the squirrel cage type blower?


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## OnlyJustME (Nov 22, 2011)

Moves more air with less noise i believe.


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## IsaacH (Aug 29, 2012)

Air filtration is a great *addition* to the use of "PPE" (personal protective equipment) however, f you have an actual allergy, you don't need to rely on a "dust mask" at all. They are considered for nuisance particulate protection. An allergy warrants actual health protection. While performing any activity that creates fine dust you should be using a respirator in ADDITION to dust removal….ie sanding or sweeping. There are soft rubber respirators availabe that are inexpensive and in my opinion more comfortable than those cheap dust masks. If you're just using the filter cartriges for dust, a respirator could actually be cheaper in the long run than the disposable masks.

(BTW, im an OSHA authorized safety trainer for the construction industry and disaster site responders)


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## ssnvet (Jan 10, 2012)

Here's your solution….










Three speed motor, timer control, remote control, very good filter….

One of the best $400 I ever invested in my shop


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## wunderaa (May 15, 2012)

http://lumberjocks.com/projects/66005

I made my own a while back. It utilizes a double-filter stack. One 4" furnace filter, fronted by an el-cheapo filter. It works great but if I were doing it again, I'd change one thing: design it to accept the largest surface area of inlet filter possible. I currently have it tailored for 16×20" filters, but there is a quick and noticeable drop in cfm when the pre-filter is getting clogged from plowing through dirty air in the shop. If you're a weekend warrior like me…build your own. You said you have access to A/C components, so pick the largest 110V squirrel cage motor/blower you can find and build the biggest enclosure you can stand to have. It'll work as well or better than any commercial unit. (MY TWO CENTS!)


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## Grandpa (Jan 28, 2011)

The squirrel cage blower will slip in the air and not over heat as easily as a regular fan with blades. The squirrel cage is more like a centrifigal pump as compare to a piston pump. At one time there were swamp coolers with fans then they all went to squirrel cage style blowers. There must have been a reason. More air? quieter? fewer failures on the motors? netter balance of the blades. Now if we could get those ceiling can people to change to squirrel cage designs. LOL


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## AandCstyle (Mar 21, 2012)

The best solution is to catch the dust at the source before it becomes airborne. This requires a true dust collector as opposed to a shop vac. Look at Bill Pentz site for more than everything you ever wanted to know about dust collection. Be aware that a dust collection system is not cheap, but is less expensive than a trip to the emergency room.

In addition to inhaled dust being an allergen, you can also develop contact dermatitis due to the dust collecting on your skin. This would require you to keep your skin covered as much as reasonable and to shower immediately after shop time.

I would strongly suggest a great dust collector if you are into wood working for the long haul. HTH


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## jaysonic (Jul 14, 2012)

Thanks IsaacH for all that info, your comment about OSHA reminded me that my father-in-law in the safety director of the school district in the area I live, he'd be good to bounce some ideas off as well.
Wunderaa, thanks for the idea about a greater surface area on the filter, as well as the link to your post. Is it beneficial to not have a cover over the air intake hole? I've seen a few designs where a grill cover has been placed there. 
AandCstyle, I'll definitely be investing in an actual dust collector. First though, I need to pinch some pennies for a while, with a 9mo. old, and a wife who doesn't work and wants 3 more kids, these things are extravagances.


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## wunderaa (May 15, 2012)

Jaysonic, the hole you see is actually the air outlet. If you're planning on having the unit mounted where someone may be able to put their hand in it, then by all means you should put a cover over it. Maybe some expanded metal of some sort…something with a low total surface area. Mine is mounted at about 8' off of the ground and I don't have any kids, so I opted to leave mine open. I do not, however, recommend a filter on the outlet side of the unit. Squirrel cage motor/blowers are designed to draw air in by creating a differential at the inlet, so it's imperative that the outlet has as little restriction as possible. Hope all of this information helps and looking forward to your solution!


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## DustPipe (Oct 12, 2012)

I would advise against the squirrel cage blower, there is a reason they are used mostly for air/fume movement. What you need to focus on is static pressure, this is what is important in moving physical dust, which as light as it may seem does have weight. You would be better served with a true flat blade style fan, running around 3450 rpm, as many filters as you can provide/afford (as this will allow the fan to work to its full efficiency) and a correctly designed pipe layout (ie. 45 deg. takeoffs and correctly calculated duct sizes). I do design, manufacture and install dust collectors for a living, so if you have any questions let me know.


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## jaysonic (Jul 14, 2012)

Dust Pipe - Here's some pics of a blower I recently found, would you say this would work fine? It's not a squirrel cage, but I've no idea how to find the static pressure on it.














































I've found a link, to APower - they say it's used for inflatables. Could this work in an enclosed box system?
http://www.apower.cc/view.php?id=8D2BpyMEo&do=product


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## DustPipe (Oct 12, 2012)

Jay- that's most likely better than plain fume blowers, as it is a higher velocity fan however it still may lack the power to lift chips and dust. There are also many variables outside of the fan to consider, ie. Shop set up number if machines, length of run. Ill bethe tied up this weekend but give me a call at 877-322-0070 Monday. Andi van help clear up any other questions


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## OnlyJustME (Nov 22, 2011)

Did i miss something? the purpose was for air filtration not dust/chip collection wasn't it? the commercial made units use squirrel cages for that to move lots more air. why use something else?


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## jaysonic (Jul 14, 2012)

OnlyJustMe - I'll be working on a DIY cyclone as well, I just want both is all.


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## kizerpea (Dec 2, 2011)

sounds like dustpipe is advertiseing…his only solution is to sell u something..at least it sounds that way to me..i built my own dust collection system..cyclone an all…piped every thing….bought the plan from woodmag an super sized it….gona build a air filter to…just waiting for the right stuff to pop up….if moneys no object the get on with it…but alot of us dont want to break the bank doing a project..advice from a DIY guy…


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## Finn (May 26, 2010)

HVAC fans have forward inclined blades because they move a lot of air quietly. One issue with them is that they will load up with dirt and become less efficient. You must use filters on the intake of these fans to prevent this. No filters on the discharge part of the system.


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## Manitario (Jul 4, 2010)

The best solution to control the amount of dust in the air is to not let it get into the air in the first place! With a good dust collection system you won't have enough dust in the air to need an ambient air filter. I spent a lot of time designing/planning a good DC system for my shop and the result is that it captures almost all of the dust at the machines before it can be thrown into the air. I have a particle counter that I've used to measure air quality in my shop while I'm working; I have less dust in the air of my shop than in the air of my house! All without using an ambiant air filter…


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## brtech (May 26, 2010)

If you are actually allergic, then you want at least two, if not 3 layers of protection. You want to start with good dust collection. Many of us use the HF 2 HP DC, but we upgrade the filter from the stock 5 micron bag to a .5 micron cartridge filter from Wynn. I think your second layer should be a Trend Airshield myself. If you want a third layer, then the air cleaner, either home brew or store bought is very helpful. I would use the positive pressure face shield religiously. The air cleaner helps to keep dust off surfaces, which is good, but the DC gets it before it gets into the air and the positive pressure face shield keeps what is left in the air from getting in to you.


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