# DIY Air Filtration



## rg33 (Dec 1, 2012)

Some time ago I updated my dust collector for a larger one and was left with the old unit. I've noticed some DIY shop air filtration systems on the web and decided to make my own. It's all made from 3/4" plywood and put together with glue and brads from a pneumatic gun. the filtration goes through three stages, the first is a cheap furnace filter to catch most of the larger particles, next is a washable filter to catch some of the medium stuff before the air is passed through the unit (I did it this way so as not to muck up the motor with dust), finally exiting the motor and propeller blades there is a more expensive filter with a Merv 11 rating to catch the particles in the 1-3 micron range. Filters size I used are 20X20". The pictures show the unit on a table, but when I was done I hung it from the ceiling, the panel with the handle faces the bottom and slides out so one can remove the filters


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## pjones46 (Mar 1, 2011)

I like the design. Have you done any tests to see if it filters more effectivly suspended vs lower?


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## rg33 (Dec 1, 2012)

I havent done any tests yet, but I work in aerospace and have access to computational fluid dynamics software; hopefully when I have some free time I would like to run some simulations with the unit mounted in different locations to see where the best place for mounting is.

thanks,


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## crank49 (Apr 7, 2010)

That fan is using about 10 times more power than a typical air filter uses.
The reason is because it is designed to produce high pressure.
Energy consumption varies as the cube of the pressure.

But, otherwise, a nice looking unit. Well made.


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## macatlin1 (May 5, 2010)

In the last picture the blower outlet looks a 'mite close to the baffle. Could be a considerable loss of performance there. I would replace that baffle with some perfboard nearer to the filter. Other than that looks good. One last question, how is the noise level?


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## rg33 (Dec 1, 2012)

Crank49 and macatlin1 you are both correct! This unit was certainly too powerful for the air filter but I had no better use for it. To your points above, at first I thought I could slow the unit down with a motor speed control but once I inspected the electrical and noticed the giant capacitor/soft start this was a no go. The closeness to the baffle was intentional due to this fact. my original plan was to remove the large (12" or so) plate covering the inlet and removing the duct end on the motor to increase air flow but this proved to increase flow so much that I nearly destroyed the third filter. So yeah the baffle and all the extras are actually there to limit flow. I like the idea of putting the perfboard (after drilling out some of the holes to an 1" or so in diameter) to not overly restrict the flow as I agree that this would make for a more efficient path.

As far as noise level, it is fairly loud but better than when the unit lived as a dust collector, Id say about as loud as a table saw maybe? I can hold a conversation albeit at a higher volume with it on

thanks for the feedback and advise


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## timbertailor (Jul 2, 2014)

The filters will become clogged in not time.

They can not handle the flow with so little surface area.


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