Build a box fan air purifier with an oversized filter

Note: There are dozens of videos of how build an air purifier with a box fan and an air filter. The issue is that they all ask you to find a 20 inch by 20 inch filter. This is a modification of their techniques that allows you to use a taller filter.
I live in a city with some of the worst smoke from the Oregon wildfires in the entire state. I watched one of the videos and then went to the local hardware store. Surprise, they were all out of the 20x20 filters.
This is the modification I came up with. I thought it could be handy for those who are desperate at the moment, like I was this morning. If you need step-by step instructions on how to tape the filter onto your box fan, just do a search for "box fan filter" or "box fan air purifier."
As always, I'm not an expert; I just needed something that works, and this really has worked. Although we're in evacuation level 2, we almost left yesterday because of the smoke levels inside our house. Since this hack, the air has improved in our house, and has allowed us to stay put.
And tangentially, if you need a break from all the doom and gloom of these wildfires, check out a video of me juggling in all the doom and gloom of these wildfires:
• 9/9/20 Oregon Wildfire...

[@justinothergrower6483]

A masterpiece.

[@dawngale3457]

Great ideas

[@chadsshow2010]

Very Cool. Did try this. Keep safe.

[@vickynoemi1]

Great idea very economical 👍✌

[@PacoWarabi]

It's definitely cheaper than staying in a hotel miles from here to try and escape the smoke. I don't know how long they will last, but they only have to make it a week or so until the smoke clears (knock on wood).

[@fiona36b]

Must give this one a try.

[@PacoWarabi]

It has made a huge difference for us.

[@vnette9777]

Genius.

[@dehydratedculture9126]

Stay safe man. I did this same thing. Taped a bunch of them to my windows too so we can let in cool air. We are in Salem

[@PacoWarabi]

Taping them to the window is a great idea! We have kept ours shut for over a week now. But with the rain last night, we are almost down to moderate smoke levels.

[@Ryan1Twice]

Problem with this I’ve noticed is air circulating in from the corners on the front side. Probably makes it a lot less efficient at actually filtering the air since not all the intake is going through the filter, but it’s better than nothing. The filter is still noticeably dirty after only a few days from this smokey west coast air.

[@PacoWarabi]

Oh, I'm sure they're not super efficient. This is definitely a temporary hack, and I wouldn't recommend this to replace an actual air purifier or HVAC filtration system. But it has made a huge difference in indoor air quality at our house, and with how disgusting the filters are after just a few days, I'm very grateful it's the filters turning brown and not my lungs. So efficient? No. Effective? Yes.

[@gorehound1313]

Ya know you can buy 20 x 20" filters, right?

[@PacoWarabi]

Read the description. We were a stage away from required evacuation due to wildfires, and the smoke was extremely bad. Almost every filter of every size was sold out at every store. I was lucky to even find the oversized filters.

[@karencanan2701]

My box fans have the plug and the speed control on the back so do you have any suggestions for how a filter could be attached? What brand box fan are you using? Maybe I can buy one on Amazon. All the local stores are sold out and like I say, I don't think mine will work with the filter attached. But it's a good idea. The air here in Corvallis in my apt. is a bit smoky, bearable but not ideal.

[@PacoWarabi]

From what I read, it sounds like you can attach the filter to the front as well. The first video I watched had the guy doing it that way. Basically, you're just trying to force air through the filter, so either putting it on the front or back should work about the same. This is just a temporary solution. I was just down in Corvallis last Sunday, and it was beautiful day for a hike. What a difference a week makes.

[@karencanan2701]

@@PacoWarabi Yeah it is a huge difference, thank you!

[@Writerdust]

Will this also work for when you cook something on the stove or you burn something in the oven? I need to get those smells out?

[@PacoWarabi]

I think it probably will, but I just built one this morning, so I don't know for sure. It has removed the smell of wildfire smoke, so that's something. I just looked at the packaging, and the MERV 13 rating specifically states it will filter odors. I'm using a MERV 11 filter because that's what they had, so you could maybe go one step up.

[@TheConpuentes]

How about putting the filter in front of the fan? Having the fan push air through the filter.