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Build a Do-It-Yourself Air Purifier for About $40

Michigan Medicine

228K subscribers • 1 video on Rounds

YouTube
  • Recommended by 5 people, in Hacker News, across 4 different months.
  • Presented by Jeffrey E. Terrell, MD, as the video describes them

For anyone, no background needed. Education, not medical advice.

2.2M views15 years ago5 recommendations

How the body worksPublic health and policy

Jeffrey E. Terrell demonstrates how to construct an inexpensive, effective air purifier using a box fan and a furnace filter.

**Current as of 2025: While the cost of materials may vary, the process and effectiveness of this option remain up-to-date. You can build an air purifier with a HEPA filter for about $40 with parts from your local hardware store and protect yourself from dust, viruses, smoke from wildfires and other lung irritants. The Environmental Protection Agency’s (EPA) Air Quality Index highlights the local air quality in your area. The higher the number, the worse the air pollution. When the AQI is over 100, using an air filter indoors, with HEPA filters or filters rated MERV 12 or higher, can help to clean the air. Air filters can help protect against colds, flu, and COVID as well. Jeffrey E. Terrell, former director of U-M Health’s Michigan Sinus Center, demonstrates how to build a DIY air purifier at home. Read: "Wildfires: How to protect your lung health in poor air quality" and more news from Michigan Medicine’s Health Lab: michiganmedicine.org/health-lab/wildfires-how-protect-your-l… *Note: When this video was made, the cost of materials was approximately $25. This has increased due to inflation. Follow Us: Facebook: facebook.com/MichiganMedicine Instagram: facebook.com/MichiganMedicine Twitter: twitter.com/umichmedicine #AirQuality #AirPurifier #AirPollution #LungHealth

Why it's here

5 people recommend this, 2 dispute it

What people say. Recommended by viewers as a simple, highly effective, and low-cost solution for improving indoor air quality and reducing allergens.

polyfractalin Hacker News • Recommends

On “Ask HN: Does anyone use something to monitor air quality in their workspace?”

If you are worried about particulate, you can build one of these: link to 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.
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dublinbenin Hacker News • Recommends

On “A small DIY air purifier”

Here's a video from the University of Michigan showing just how effective these cheap DIY air filters can be: link to this video
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shardin Hacker News • Recommends

On “At JPMorgan, productivity falls for younger employees at home”

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: link to 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
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Qub3din Hacker News • Recommends

On “Smoke has caused temperature forecasts to go crazy”

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: link to 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
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thomasin Hacker News • Recommends

On “Experiments on a $50 DIY air purifier that takes 30s to assemble”

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: link to this video
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apoin Hacker News • Disputes

On “Build a do-it-yourself home air purifier for about $25”

Nifty idea, but I'm not sure I agree with the technique used to prove effectiveness: link to 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 t…
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chewzin Hacker News • Disputes

On “A small DIY air purifier”

This seems like useless toy. You should be aiming for something larger that would work for an apartment. 1 link to this video 2 link There is thousand vidoes on Youtube on how to DYI one.
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vymaguein Hacker News • Mentions

On “Cleaning sprays have an impact on lung health comparable to cigarettes”

But I thought it has been shown putting simple furnace filter on a fan is good enough. link to this video Are you talking about other filters to filter the larger particles, and carbon filters? Because aliexpress sell them too.
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meesterdudein Hacker News • Mentions

On “Air pollution linked to “huge” reduction in intelligence”

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. link to this video
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bryceaccin Hacker News • Mentions

On “Monitoring my home's air quality with AirGradient's DIY sensor”

link to 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
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fadyin Hacker News • Mentions

On “Ceiling Air Purifier”

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: link to this video
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