# Homemade Air Filtration System



## dwendt1978

Just a little 900 cfm oven hood fan. Everything was free or on hand so I figured it would be worth a shot. It's sized for 14 x 20 x 1 inch filters. With the lights off and a flash light you can see it sucking in very fine dust particles. I have a large furnace squirel cage blower that I plan on building a large one if this works.

More to come......


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## ACP

Interesting, never thought of an oven hood for this. I'll be curious to hear how it works. Thanks for posting this. I get so many ideas from these types of posts.


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## rrbrown

Interesting idea for sure. you said it suck in fine dust is that with the filer in place? What kind of filter? I would recommend using 2 filters. one of the cheaper ones in front of a HEPA filter. That way you can make the more expensive HEPA filter last longer by changing out the cheap one used as a pre-filter.

However I'm wondering if that little fan will be sufficient going through the filters.


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## dwendt1978

*Sorry for the delay*

So hard to get out in the shop with 2 little kids and a wife that runs a business out of the house. 

But it's working great so far. The filter is getting brown. I have a pre-filter a cheap 67 cent one (that's only good for catching gravel) and a pleaded filter that cost 3.47. The really good ones are 16 bucks. It turns on with a light switch that I had laying around with a different colored switch cover. Hey this was a budget project. But has convinced me to build one with a furnace blower. 

I have some rare earth magnets that I'll use to keep the door shut better and I'll add a space between the filters. All in all I'm happy. It proves to me you don't need to spend alot of money for an air filtration unit.

Total cost-4.14 plus tax. Everything else was on hand.


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## low

The total cost is insane. Great work. :thumbsup:


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## bob sacamano

i had no idea the hood fans moved 900 cfm ! i saw a window in your shop. as long as you have an outside wall is there any chance you can exhaust the dust outside instead of filtering it ?


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## tvman44

I use a $30.00 20" box fan from Wally World with a couple of "J" channel strip to hold a 20" x 20" filter also from WW and it works so well thinking about getting another fan and mounting 2 "J" channels together at the top and bottom so I can us a pre filter and if that works out Ok I will add a 2nd J to the first fan. The fan serves 2 purposes, it filter the air and creates air movement which I was doing already with a round fan on a stand and will stop using the round fan after I get the 2nd box fan.


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## Clouseau

*fan adaptor*

I saw an add online where a guy is marketing a plastic adaptor to fit the box fans and holds a filter.
Dan Coleman


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## SteveEl

Neat idea, using the range hood fan. I too have an old squirrel cage blower from an old furnace, and plan to make a cabinet for it.... but now I'm wondering whether the box fan option is just as good and cheaper to operate?


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## yocalif

SteveEl said:


> Neat idea, using the range hood fan. I too have an old squirrel cage blower from an old furnace, and plan to make a cabinet for it.... but now I'm wondering whether the box fan option is just as good and cheaper to operate?


If the old furn blower is belt drive, then no question go with the furn blower. Direct drive can be pretty noisy. One consideration of the furn blower, they are designed to work against static and still deliver the necessary CFM. Depending on horsepower & blower size, 1200,1400,1600, 2000 CFM is possible. Typical blower motor sizes would be 1/3-3/4 hp so lower hp lower CFM. Regarding static using the furn blower, you could have 3 or more filters and get plenty of CFM. So a straight filter like the pic in OP that would pic up all the heavy stuff (and be changed frequently), then two pleated filters in configured in a V with the point of the V facing into the airflow, This will give you double the surface area and should remove up to 99% of all the remaining particulate. In addition most furn blowers are capable of 2 to 4 speeds, so if you are lucky you could have a 3 speeds, thus wire it so the low speed is the normal almost always on speed, and whenever you power your TS, or another high dust generating equipment it would kick into high speed.


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## lray

great idea. nice way to re-purpose some parts and save a ton of money!


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## <*(((><

yocalif said:


> If the old furn blower is belt drive, then no question go with the furn blower. Direct drive can be pretty noisy. One consideration of the furn blower, they are designed to work against static and still deliver the necessary CFM. Depending on horsepower & blower size, 1200,1400,1600, 2000 CFM is possible. Typical blower motor sizes would be 1/3-3/4 hp so lower hp lower CFM. Regarding static using the furn blower, you could have 3 or more filters and get plenty of CFM. So a straight filter like the pic in OP that would pic up all the heavy stuff (and be changed frequently), then two pleated filters in configured in a V with the point of the V facing into the airflow, This will give you double the surface area and should remove up to 99% of all the remaining particulate. In addition most furn blowers are capable of 2 to 4 speeds, so if you are lucky you could have a 3 speeds, thus wire it so the low speed is the normal almost always on speed, and whenever you power your TS, or another high dust generating equipment it would kick into high speed.



Air handlers from an HVAC setup are really nice because of the potential of the 2-4 speeds. Call around to local HVAC companies and see if they have any used that you could purchase. I have thought about making a second one just for kicks. I already have a jet ambient air cleaner that I got off craigslist for a song.


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## Sleeper

I’m noticing a little dust in the air of my shop even after blowing it all out with a leaf blower. 

I want to build an air filtration box hopefully this weekend. I believe I have all the materials, but still trying to figure out the best way to do it. I can’t decide if I want to mount it to the ceiling and have the fan blowing downward with filters all the way around or set it on top of something like my refrigerator and blow toward the door with a filter on only one or maybe two sides.

I wish I would have thought about the air handler last year because I hailed one off to the dump.


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## woodnthings

*have it exhaust to the door*

If you are working with any papers the downward exhaust will be frustrating. Sideways will give better circulation than down.
The exhaust fan in the wall or ceiling makes a big difference also.
If you happen to make a bunch of dust it can change out the air in a few minutes. Also odors from chemicals or finishes.  bill

I also have 2 el cheapo 3 speed ceiling circulating fans for the hot summer months here. They seem to make the shop feel cooler even if not by actually lowering the temperature.


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## Sleeper

woodnthings said:


> .......The exhaust fan in the wall or ceiling makes a big difference also.
> If you happen to make a bunch of dust it can change out the air in a few minutes. Also odors from chemicals or finishes.  bill
> .......


 Thanks Bill, If I was going to stay in this place after I retire in a few years, I would cut a 2’x2’ hole in the wall for a vent, but I have stucco walls and masonry is just not my thing. I have a screen door in the back that I usually put a box fan on the floor to blow air in, but it’s just not the same as sucking it out. I haven't tried turning it around.


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## Carvel Loafer

Thanks for the idea on the air filter box. :thumbsup: I've been thinking of building one or two for my shop. My shop has a wood stove on one section that I would benefit from moving the air gently from the warmer side to the part where my workbench is. I could use your idea to do that and filter the air at the same time.

Let us know how the squirell cage fan version works out; I have many recycled fans that I can pick from including squirell cages.


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