Air purifier out of 20" fan

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Project by BOBAH posted 09-20-2017 07:29 AM 2568 views 8 times favorited 14 comments Add to Favorites Watch

Hi there. Here is my take on workshop air quality problem. I tended to ignore it until recently, when I purchased Dylos Air Quality Monitor. It is counter of particles in the air, calibrated to count particles of two sizes, especially hazardous for health, and allows to continuously monitor air quality.

Not only did it confirm that my air becomes dusty after sanding, cutting, sawing, but also showed how bad it gets sometimes. The next logical step for me was building an air filtering system. As constant noise could become an issue in itself, I realized that the largest-diameter fan produces the highest flow on lower RPM, which translates to lower frequency noise that is easier to tolerate.

Combining this square 20-inch fan with 20” HEPA filter (by just leaning filter on the fan and seeing it getting sucked onto the grid) instantly showed very promising results – the pollution level dropped 100 times faster than without any filtering, and this particular fan is very quiet even on high speed. So my next project was to build a casing for fan and filter, and put it in some place in the workshop where it is out of the way.

The box is built out of .75” birch plywood, pocket screw joinery. I didn’t have to disassemble the fan or even remove its feet – it would be easy to take it out if needed. It is also easy to replace filter – they both are held in place by two eccentric latches pushing them against narrow fences around perimeter. The box is hanging from the ceiling on plastic chains capable of holding 50lb weight – above my height, I won’t be able to bump my head. The controls are facing down, so I can turn it on and adjust speed without a problem.

I added a handle on a side in case I will ever have to move it around. There is also a little shelf for air monitor, and power outlet to power it. Finished building it today and already enjoying it – fan is out of the way, I keep it constantly on, and it doesn’t take precious power outlet to run – I am using the one on the ceiling. Overall, it cost me about $50 in parts and materials (not counting air monitor).

14 comments so far

View ChrisK's profile


2059 posts in 4372 days

#1 posted 09-20-2017 11:47 AM

I have used one of these for a few years now, works pretty well.

Yours looks nicer than mine.

Nice work.

-- Chris K

View helluvawreck's profile


32122 posts in 4157 days

#2 posted 09-20-2017 01:44 PM

This is a nice setup. Congratulations.

helluvawreck aka Charles

-- helluvawreck aka Charles,

View Scott's profile


119 posts in 2646 days

#3 posted 09-20-2017 02:29 PM

You’ve inspired me to build one. I’ve been thinking about it for a while but just haven’t got around to it. And I was really curious to how well they worked. Thanks for the info!

View BurlyBob's profile


9414 posts in 3556 days

#4 posted 09-20-2017 03:57 PM

A few years back I built something similar to yours and it’s amazing just how much saw dust you can clean out of the air. Your going to be very pleased with yours. It’s a very nice build.

View LesB's profile


3146 posts in 4734 days

#5 posted 09-20-2017 05:34 PM

This type of filter system has been shown a number of times and is quite effective.
I made mine 20 years ago from a used HVAC (house furnace) squirrel cage type blower. I got my blower when I replaced my heating system but a local heating contractor will probably give one to you if you ask. It is very quiet and moves a lot of air. In addition it does double duty by circulating the heat from my wood stove. Built into a floor cabinet with wheels the top also serves as my sharpening station.

-- Les B, Oregon

View Desert_Woodworker's profile


8465 posts in 2505 days

#6 posted 09-20-2017 10:27 PM

Very nice. I like the air monitor as well, nice touch.

-- Desert_Woodworker

View MT_Stringer's profile


3183 posts in 4522 days

#7 posted 09-20-2017 10:42 PM

“Air purifier out of 10” fan”

Confusing to say the least.

-- Handcrafted by Mike Henderson - Channelview, Texas

View Desert_Woodworker's profile


8465 posts in 2505 days

#8 posted 09-20-2017 11:18 PM

Could he have made a typo error 10 instead of 20? To me this looks like a 20” box fan- nice job.

-- Desert_Woodworker

View woodbutcherbynight's profile


10526 posts in 3700 days

#9 posted 09-21-2017 01:02 AM

Nice work, the white chain is classy.

-- Live to tell the stories, they sound better that way.

View Desert_Woodworker's profile


8465 posts in 2505 days

#10 posted 09-21-2017 01:26 AM

Yes! You made it to #1. As Stumpy Nubs says, ” You deserved it my friend”

-- Desert_Woodworker

View BOBAH's profile


159 posts in 2634 days

#11 posted 09-21-2017 06:03 AM

Indeed, it’s 20” fan, fixed the title :-)

View MT_Stringer's profile


3183 posts in 4522 days

#12 posted 09-21-2017 05:28 PM

Indeed, it s 20” fan, fixed the title :-)


Thanks. Now I realize I have a similar set up, just not as fancy as yours. It sets on the table saw fence supports to help capture dust from above the saw. Works well. I keep a couple of spare filters for it and vacuum it often. Note I also have a Grizzly air purifier that is hanging from the ceiling over the work bench.

-- Handcrafted by Mike Henderson - Channelview, Texas

View woodsawdustmaker's profile


46 posts in 4915 days

#13 posted 09-27-2017 02:15 AM

In addition to my Delta Dust Collector, I hung a similar 20” box fan with a filter from the ceiling above the left side of my radial arm saw. The dust collector does not get all of the finite particles of dust that float into the air and the fan/filter help pick up some of the missed dust.

-- Max - Birmingham, AL

View daiku_padawan's profile


108 posts in 1520 days

#14 posted 01-29-2018 05:32 PM

Nice to see I’m not the only one to think of this.
Nice mount for your setup.

-- ~Daniel

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