20x20 Fan With Air Filter.




About: Retired and live in a little trailer park. I have a bunch of computers networked together that I mess with. We go to the gym. Spend a lot of time going between here and the hospital for different problems th...

History: First off, a little history of how this project got started. I use 20X20 box fans. I have one in the window and every couple months, I have to pull it down and clean the fan and the screen that is on the window. This would be a good project for me to work on.
To use the box fan and a 20x20 filter, I wanted to make it easy to change and with little or no cost.

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Step 1: Checking Out the Bottom Bracket.

Step #1.This step you will see the pictures on the metal that I used to make the brackets that I needed to hold the filter and the fan. I going to start with the bottom bracket. It is made of channel that is 1/4x1/4x3/4 medal. The brackets are 2 1/2 inches long. On this part, I drilled two holes. One the same size of the screw that I took out and the other one big enough to get my screw driver in to put the screw in. There is one bracket on each side. These brackets hold the bottom of the filter.

Here I show the picture DSCF0122.

Step 2: Checking Out Top Bracket.

Step #2 This is the top bracket. As you can see by the picture the bracket is upside down. The flat side is down. Also I had to drill a few more holes in this one. These holes are all the same size. Big enough for the screws to go through. As you can see by the picture, this is a much longer screw. It goes through all three holes plus the fan. I used self starting screws so I put this one in with my screw gun. It needs to be loose enough so that the outside medal part will spin. That part is also 2 1/2 inches long. It is 3/4 wide.

Here I show the picture DSCF121

Step 3: Bottom Bracket With Filter In.

Step #3 On this step I will show the bottom bracket with the old filter in it. When you put the filter in, put the bottom of the filter in first.

Here I show the picture DSCF0120

Step 4: Top Bracket With the Filter In.

Step #4. Again here we are on the top bracket. You will see the medal part (3/4 x2 1/2) that is locked down to hold that top of the filter in. The bottom of the filter sets in the channel.

Here I show the picture DSCF0119

Step 5: Air Filter Before Removal.

Step #5 Here you will see a picture of the filter before I changed it. This is after being in the window for a little over a week. The filter is on that I bought at Lowes for 69 cent each. I bought 24 for less the 20 bucks. There are 30 day filters. I think for that price that maybe I can afford to change them earlier. Maybe every 2 weeks.

Here I show picture DSCF0118

Step 6: Here Is Fan With New Filter Installed.

Step #6 Here you will see a picture of the new filter that I put on my fan. Changing the filters takes only a couple minutes. I take a bench brush and hit the out side on the fan with it running before I put the filter in. This removes any dust that is on the outside of the fan. Another thing, some of the new fans have the plug right on the motor so with these you have to punch a hole in the filter to plug it in.

Here I show picture DSCF0123

Step 7: Front of the Fan All Ready to Go.

Step #7 and the last step. Here you will see a picture of the fan from the front with the filter installed. Ready to collect more dust.

Here I show picture DSCF0124

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    18 Discussions


    4 years ago on Introduction

    I used this kind of filter for years. I couldn't afford a fancy air filter and then realized that a furnace filter is 20x20" just like a box fan.

    I just duct-taped the filter to the box fan which makes a perfect seal. If you use white duct-tape, it's not even that ugly.

    I would spend more money on the "HEPA" filters but, as an allergy sufferer, I figured that's what I needed.

    I can't image that the cheaper filters get out the really small dust.


    5 years ago on Introduction

    Wow its an cool solution for indoor air pollution. One of my friend also made an awesome product like this name Fan Buddie. Its an air purifier. Its a very unique product. I am using it. I bought it from https://www.fanbuddie.com/


    I'm going to try this with bolts in the frame and fender washers to hold the filter on! Thank you for the post!


    6 years ago on Step 2

    Try drilling hole in one end of channel close to the edge. One small for screw one large for screwdriver to get to screw. Place channel turned over so that it faces down. I useda machine screw with lock nut through the existing hole. channel pivots down to hold filter. had to take off guard on other side to get nut on screws.

    1 reply

    Reply 6 years ago on Step 2

    Thanks for looking at my instructable. It really works good for us. It only takes a couple seconds to change the filters. We use one in the window to catch the dust. We have 3 set up so we can use the other two where we think that we may need them. I put one in the shed and took my blower and started blowing the dust around so that the filter could catch the dust. Well thanks again for the comment. Chuck


    Reply 7 years ago on Introduction

    Thanks for the comment. The fans have a speed control on them. Either 2 or 3 speeds. Not sure. Probably if you wanted you could put a variable controler on one.


    8 years ago on Introduction

    By the way, cateddy's design is really nice. I'm just too lazy so I used blue tapes.

    These 20" box fan are just awesome!

    1 reply

    8 years ago on Introduction

    Easier way: tape the filter to the fan box with some blue tapes.
    Better filter: 3M filtrete 1500, worked great w/o extra noise. (3M filtrete1000 cheaper alter.)
    Longer filter life: add extra fiberglass pre-filter(s) before 3Ms.
    Better Fan: Fan w/ remote, or add a remote on/off switch to your existing one

    Put these around home, and saved.
    No more expensive HEPA filters/air purifier needed. :D

    1 reply

    Reply 8 years ago on Introduction

    Thanks for the comment Xyzo. The filters that I use cost 69 cents each. I don't think that you can beat that price. For what I am using them for, they work really well. The last box of filters that I bought, I just had Home Depot order me a box. They didn't charge me shipping and they gave me a 10% discount. One thing for sure, the filters sure helps keeping the fan clean. Thanks again for the comment and for checking out my project. Chuck


    9 years ago on Step 5

    The problem with this box fan is the airflow is not even.  Which caused the suction not pull evenly,  minimize the filtering process.  I made one the same concept except, instead of directly attach filter to the fan.  I build a box out of construction foam about 5in deep to create a air volume which caused the air suction to be more even.  I get a full evenly distribute dirt on the filter.  Optimize the performance of the air box fan.

    1 reply

    Reply 9 years ago on Step 5


    This is the first one that I made and I think that it would be more to your liking. It has 2 filters, one on each side. I don't have pictures of it. I gave it away when I moved away in around 2005. I used it at work for different things. For paint and also for the dust. This filter would do what you were talking about. Cover the whole filter. I had a big fan motor on it with lots of horses power. Sorry about not answer you comment earlier. I don't check this email too often. Thanks for the comment. Chuck


    Reply 10 years ago on Introduction

    Hello Buenafe. Sorry about not replying to your comment. This went in my spam box. I use 2 of these fans just about everyday. One is in the window and the other I set in the hallway. Here in California is like living in a dust bowl.


    10 years ago on Introduction

    Thanks for the comment. Check back I have another one that I am working on for paint. I took that first picture that I made in paint and redoing it. I am putting a dryer pipe on it to where you can run the stuff out side just like the dryer do.


    10 years ago on Introduction

    cool! I've been wanting to get one of these from dick blick for around $300 bucks for ventilating paint thinner odors and such.