5 HN users recommended this tutorial4 months2012–2022score 4.5
Years with an HN recommendation, 2007–2026
HN people link it during wildfire smoke and air quality threads as a practical, cheap fix, though a few doubt how rigorously its effectiveness was shown.
A University of Michigan Medicine demonstration of building a cheap DIY air purifier from a box fan and a HEPA or high-MERV filter using hardware-store parts. It explains why this helps against dust, smoke and viruses and ties it to local air quality readings.
“Here's a video from the University of Michigan showing just how effective these cheap DIY air filters can be” (HN, 2020)
If you are worried about particulate, you can build one of these: [this video] I built one for my room because my previous tenants had cats, which I'm allergic to. Even after steamcleaning our apartment I was chronically congested. Built one of those purifiers and a few days later most of my symptoms are gone. It's been about a month now and the filter is noticeably soiled.
DIY purifier relieved commenter's allergy symptoms within days.
If this is because of high PM2.5 concentration (due to wildfires or otherwise), I suggest building a DIY air filter, such as the one in the video here: [this video] When the Air Quality Index shot up to ~150 in my area (you want to keep it below 100, preferably below 50), I went to Home Depot and bought box fans and furnace filters and built my own. You can check the air quality in your area on this site: [link]
The University of Michigan made an instructional video showing how you can easily make an air purifier out of a box fan and a HEPA-rated furnace filter for $25: [this video] It won't be as good as a purpose-built machine, but it will be far better than nothing at all. TheWirecutter found it reduced particulate matter in a room by 87%, if you do it right. They also make clear important caveats about this method -- in short, this works in a pinch, but probably should not be used in place of a purpose-built filter if you want one for year-round use. [link]
Instructions for making a box fan and furnace filter purifier.
Yeah, same thought. Something like the Coway air filter ( [link] ) regularly sells for under $200, and it is going to be much quieter than this option. It also has been tested fairly extensively from what I've seen, it's EnergyStar approved, etc, and it has a built in sensor. It doesn't look too bad either. But I understand the point, especially in times when you can't find a purifier. Also, good video on all this: [this video]
But I thought it has been shown putting simple furnace filter on a fan is good enough. [this video] Are you talking about other filters to filter the larger particles, and carbon filters? Because aliexpress sell them too.
I know a certain framework creator that will be all over this - and has been vocal on twitter about it. I went looking, this seems like a pretty good air quality monitor: [link] (~$400) There are cheaper ones too; but do your research, as accuracy (and ideas about what constitutes accurate) can vary from manuf. to manuf. [link] also apparently, a box fan + filter ain't so bad. [this video]
[this video] you just put a fan filter on the back, you can increase the amount of filters to not hurt the fan motor as much by making a triangle config or fan on top of 4 filters in a cube. fans are for air throughput not static pressure so real air purifiers have squirrel cage blowers
Fan filter design tips on airflow versus static pressure.
Reminds me of this video that came from University of Michigan during one of California's fire season when many fires were ablaze and air quality was terrible: [this video]
University of Michigan video from a California fire season.
Nifty idea, but I'm not sure I agree with the technique used to prove effectiveness: [this video] The narrator puts a particle counter in front of the fan and notes the 90% reduction. So far so good. The problem is extrapolating this result to the entire room. Yes, maybe you'd get close to 90% if the device were allowed to run a few days. On the other hand, it could leave the situation worse (by blowing existing particulates around) or unimproved (by failing to filter room air efficiently enough. Either way, I'd like to see see a controlled study. Two identical rooms with identical usage. One gets a homemade filter. The other gets just a fan of the same make and model, maybe with a dummy filter to baffle airflow. What's the average particle count in both rooms after, say one week?
This seems like useless toy. You should be aiming for something larger that would work for an apartment. [1] [this video] [2] [link] There is thousand vidoes on Youtube on how to DYI one.
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