Box Fan Shop Filter

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Project by TheWoodenOyster posted 02-05-2014 06:43 AM 34134 views 53 times favorited 21 comments Add to Favorites Watch

Hey guys,

So I am between jobs right now so I thought I’d knock out some of those projects in the back of my head. One of those projects was a shop filter made from a box fan and plywood scraps.

I saw a thread the other day about shop filters. I have always thought a shop filter would be nice to have, but I wouldn’t want to blow a bunch of money on one. So, like many of y’all, I decided to build my own. I made it out of some scrap plywood I had sitting around. I made the box so that the filters and fan can be removed from the side. Some wooden tabs hold a removable side piece on, and when you need to change the filter or use the fan, you just remove the side piece and take out whatever you want. I included in the box 2 places for 1” thick filters, 1 place for a 5” filter, and a place for the fan.

Photo 1: Completed filter hanging over the tablesaw
Photo 2: Filter box with removable side sitting next to it
Photo 3: Filter box with a filter and fan inside
Photo 4: Different view of filter box with filter and fan inside

I hope to keep at least two 1” filters in it most times. I made the spot for the 5” filter so that one day I can put a 20”x20”x5” MERV 16 filter (which catches 99% of .3 to 1 micron dust) in it. Those filters alone are about $100, but one per year isn’t too bad. I am hoping that a “sacrificial” 1” filter in front of it will help get most of the big stuff and prolong the life of the fancy filter.

I built this project because I felt that it could do almost as good of a job as a fancy rig with a few cheap filters. With the MERV 16 filter in it, it will outperform $700 machines. Hope you guys like it.

Here is a link to the MERV 16 Filter I was looking at:


-- The Wood Is Your Oyster

21 comments so far

View doubleDD's profile


10429 posts in 3162 days

#1 posted 02-05-2014 12:13 PM

Your box filter will perform just as good as the expensive ones with the same filters in it. I bought mine and added a pre filter in front of the two it came with to catch the big stuff first . Works great and doesn’t interfere with the cfm. Yours is a great version of those. Nice build. Well done.

-- Dave, Downers Grove, Il. -------- When you run out of ideas, start building your dreams.

View Ken90712's profile


18028 posts in 4307 days

#2 posted 02-05-2014 12:17 PM

Nice work, had one of these for a long time…. Enjoy…

-- Ken, "Everyday above ground is a good day!"

View eztrigger's profile


162 posts in 3046 days

#3 posted 02-05-2014 01:57 PM

can you give us a feel for the improvement it has made in air quality? I keep considering making my own, but I am not convinced the smaller fans can move enough air to be effective.

-- "Some get spiritual 'cause they see the light, and some 'cause they feel the heat." --Ray Wiley Hubbard

View  woodshaver Tony C   's profile

woodshaver Tony C

8070 posts in 4472 days

#4 posted 02-05-2014 03:00 PM

Nothing like having clean air in the shop. I made one with the same fan but with one filter for inside the house. I find that the fan does slow down quite a bit with just having a single filler. You can see my fan filter here.
I also tried the using the same pleated filter as I see in you photos and it slowed the fan down a bit more.
I made one for my daughter’s bird room and that fan does collect most of the floating bird dander in the room.

-- St Augustine FL, Experience is the sum of our mistakes!

View TheWoodenOyster's profile


1335 posts in 3054 days

#5 posted 02-05-2014 04:12 PM

Eztrigger, I will let you know how it changes the environment in the shop. I’ll need a few weeks to get a good feel for it, but I’ll try to remember to put the results on the project comments. Also, looks like you might be the second aggie I have encountered on here is the last week. Gig em!

-- The Wood Is Your Oyster

View LesB's profile


3011 posts in 4562 days

#6 posted 02-05-2014 06:42 PM

Everyone should consider having an air filter in their shop.
I think the squirrel cage blowers do a better job of moving the air than a box fan. Many people (including myself) have gotten them from old house furnace blowers. Some even have multiple speeds.
I built mine into a floor cabinet with wheels so I can move it closer to the source of dust when necessary. The top serves as a sharpening station. Most of the time it is also used to circulate the heat from my wood stove.

-- Les B, Oregon

View TheWoodenOyster's profile


1335 posts in 3054 days

#7 posted 02-05-2014 08:04 PM

Yeah, I would like to have a squirrel cage type one day, but the fan was nice and convenient (and free), so I went with that.

-- The Wood Is Your Oyster

View Maveric777's profile


2694 posts in 4195 days

#8 posted 02-05-2014 10:03 PM

Looks pretty handy to me! Well done…

-- Dan ~ Texarkana, Tx.

View Richard's profile


11310 posts in 4151 days

#9 posted 02-05-2014 10:46 PM

Very Nice Project Indeed! Beautiful Work! Thanks For Posting!


-- Richard (Ontario, CANADA)

View fivecodys's profile


1740 posts in 2755 days

#10 posted 02-05-2014 11:06 PM

I like it.
At first I thought you had left a space for a second box fan to help increase air flow. Of course as I read your text I now understand what the space is for.
Nicely done!


-- A bad day woodworking is still better than a good day working.

View mike02719's profile


303 posts in 4905 days

#11 posted 02-06-2014 02:08 AM

Real good idea. I made mine from an old hot air furnace blower. I put in two regular furnace filters. It was mounted right over the table saw for three years. I was satisfied with it until I saw the manual for a store bought one. Thay recommended mounting it near a wall so you get a circulating effect. I did this and the difference was dramatic.

-- Mike, Massachusetts

View woodbutcherbynight's profile


9589 posts in 3528 days

#12 posted 02-06-2014 02:20 AM

+1 LesB I just got two and am making a box for the crawlspace as well as one for a friend. Free is always good and they are throwing them away 4-5 at a time.

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

View changeoffocus's profile


467 posts in 2736 days

#13 posted 02-06-2014 02:36 AM

Nice workmanship, before you spend money on a Merv 16, I’d recommend you check out the static pressure drop that it takes for that fan to work. I have a similar home built in my workshop drawing that uses a discarded inline fan. I’m only using Merv 8’s at this time. See my workshop picture if you are interested I can give you more information.

View SkinsKaos's profile


11 posts in 3047 days

#14 posted 02-06-2014 06:05 PM

nice build!

I need to put one of these together for my shop ASAP!

It was touched on earlier in the comments, Can you use 2 box fans (maybe with a filter between the 2)?

View TheWoodenOyster's profile


1335 posts in 3054 days

#15 posted 02-06-2014 06:11 PM

Now that using two fans has been mentioned, I bet I could do that. Sort of like a turbocharger for a shop fan! I will definitely give that a shot if I notice that decreased air movement becomes an issue. Thanks for the idea guys!

-- The Wood Is Your Oyster

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