Shop Built Air Filter

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Project by OldKranky posted 01-15-2012 02:25 AM 24105 views 112 times favorited 38 comments Add to Favorites Watch

I scored a free 4 speed furnace blower the other day and decided to build a much needed Shop Air Filter system. I found some plans at
All it cost me was $30 for the 3/4 Birch plywood and a few hours of my time.

Note: Thanks to LJ Rance for showing me his disposable Kerfmaker that I used to make the slots for the sliding cover plate. It worked like a charm on the first try.

You may notice the filler boards for the filters. I built it for 16×25 filters but had scored a dozen 14×25s form the local Re-Store for $1 each a few days ago.

Thanks for looking at it …...

-- Better looking at it than for it....

38 comments so far

View SwayzeeJon's profile


14 posts in 3365 days

#1 posted 01-15-2012 02:36 AM

Looks great! Let us know if it works as well as you hope it will.

-- "Have you ever heard the phrase, 'Give a boy a video game and he'll play all day - teach a boy a video game and he'll play for life?' Me neither - take him fishin!" - Bill Dance

View LesB's profile


2882 posts in 4459 days

#2 posted 01-15-2012 03:00 AM

Old furnace squirrel cage blowers work great. You did a nice job.
I put mine into a larger cabinet with wheels so I can roll it around to different locations when needed.
Mostly I have it blowing across my wood stove so it also circulates heat in the shop. You know how cold and damp the Northwest can get in the winter (-:
I use a double layer of filters, a coarse outer filter and a finer inner filter.
The top of the cabinet is used for my sharpening center where my grinder and slow speed wet sharpener are mounted. Extra space in the cabinet under the blower section is used for storage. The blower has lasted 15 years but I have a spare if it ever goes out.

-- Les B, Oregon

View Gabe C.'s profile

Gabe C.

288 posts in 3357 days

#3 posted 01-15-2012 03:02 AM

I’m adding this to my favorites. I need this for my garage shop!

-- If I could just get this whole "Time/Money" problem figured out...

View Dusty56's profile


11863 posts in 4704 days

#4 posted 01-15-2012 03:25 AM

Very nice looking project : )
I wish I had thought of doing this before spending so much money on the store bought one.

-- I'm absolutely positive that I couldn't be more uncertain!

View HorizontalMike's profile


7913 posts in 3930 days

#5 posted 01-15-2012 03:39 AM

Major envy here! The furnace blowers are hard to come by cheap.

-- HorizontalMike -- "Woodpeckers understand..."

View NormG's profile


6508 posts in 4019 days

#6 posted 01-15-2012 03:55 AM

What, sounds like an excuse to do wood working. Nice job, will put on my list

-- Norman - I never never make a mistake, I just change the design.

View a1Jim's profile


118161 posts in 4593 days

#7 posted 01-15-2012 04:07 AM

A great shop filter job.


View ortega5629's profile


7 posts in 3347 days

#8 posted 01-15-2012 04:14 AM

I’m so bummed i just replaced my furnace with a full functioning blower. I wish i had the foresight to have kept it. Well done!

View tinnman65's profile


1413 posts in 4430 days

#9 posted 01-15-2012 04:50 AM

I have one of those blowers that I saved from a furnace years ago. Thanks for posting this ,I really should get this made for my shop. I really like the retro fit filters, I just picked up some at Lowes that had been opened for 50 cents and they just happened to fit my furnace but they had several sizes for the same price. Nice work!

-- Paul--- Creativity is allowing yourself to make mistakes. Art is knowing which ones to keep. — Scott Adams

View longgone's profile


5688 posts in 4324 days

#10 posted 01-15-2012 04:55 AM

You did a really nice build for your filter. What made you decide to use 3 filters for the intake side? I have several I built for my shop and I use just one filter…but wonder if more intake filters would be better if it wouldn’t restrict aid flow.

View grumpy749's profile


228 posts in 3393 days

#11 posted 01-15-2012 05:01 AM

I used a single filter on each side of my version but i like your stack idea. I have to blow my filters out with compresed air at least once a week. I used hepa one micron filters and I love the way it cleans.

-- Denis in Grande Prairie. Yesterday is history, tomorrow is a mistery, but today is a gift. That is why it is called the present.....Pink !

View Grandpa's profile


3264 posts in 3691 days

#12 posted 01-15-2012 05:03 AM

Greg the “store bought” air filters have a pre-filter an then a better filter that is rated for .5 micron. I think the best thing would be to bite the bullet and get the $50 .5 micron filter for the home made systems. It would really clean the air. The pre-filter would remove a lot of the nasty stuff before the inside filter removed the really fine dust.
Kranky, your system is nicely done. good job

View OldKranky's profile


142 posts in 3348 days

#13 posted 01-15-2012 05:19 AM

Thanks everyone for your comments.

I have two filters on the intake and one on the exhaust side. I built it as the plan showed.

-- Better looking at it than for it....

View Bearpaw's profile


270 posts in 4736 days

#14 posted 01-15-2012 06:02 AM

I built the this about 10 years ago and it has worked great. You will enjoy it. I have mine mounted to the ceiling directly over my table saw. It helps in moving the air to heat up the shop.

-- "When we build, let us think we build forever." John Ruskin

View Eddie's profile


27 posts in 3346 days

#15 posted 01-15-2012 06:53 AM

Thanks OLDKRANKY i just moved into my new shop working on a router table now but the air system will be next thanks for the post and the kerfmaking jig i need it for the table now fan box looks good and Bearpaw had one for 10 years so im going with it. as soon as i get a good camera ill post my new shop

-- Jesus is ok with me

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