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.

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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.

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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.

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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.

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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.

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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.

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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.

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