How to Make a DIY Air Purifier

I’m on a quest to make a DIY air purifier. Step one was my research into how different filters work. Based on that, I concluded that a HEPA filter is all you really need to make an effective air purifier and fight particulate air pollution somewhere like China or India. Given the fact fancy air purifiers run for 8,000 RMB in Beijing, or 100,000 INR in Delhi and most people don’t have that kind of money, I thought I’d try making my own DIY air purifier.

Wait, Does the DIY Purifier Actually Work?

I give data on how well this DIY air purifier works here (1, 2, 3, 4), but here I’ll explain how I made it.

How to Make a DIY Purifier

#1 Buy a fan

It’s important that it has a flat front or back so that you can strap the HEPA filter to it.

Fans with flat fronts usually have a recessed motor unit, so look for that. Here’s the one I bought for 58 RMB (about US$8.50):

diy air purifier fan


#2 Buy a HEPA filter

For my very first homemade air filter, I first bought this one for 108 RMB (US$16):


HEPA filter for homemade DIY air purifier


Since then, I tested HEPAs from all the manufacturers I could find to see if I could make an even more effective DIY air filter, and found one that captures more particles and has better air flow. Because I buy it in bulk and ship it through the shop for my social enterprise, it costs less (75 RMB) than that first HEPA I bought. I’ve tested this HEPA filter with my particle counter, so I know it works (watch live DIY filter test here).


#3 Pull the grating off the front of the fan

This is where the DIY fun starts! It helps if you have pliers for this. Then turn the power setting to 3 and pull the knob off – we’ll be using this DIY air purifier on the highest setting.

The knob gets in the way of the HEPA. Without the knob, I turn my DIY air purifier on and off by plugging and unplugging it.


Step 3 in making a DIY air purifier


#4 Strap on the HEPA

Use string to strap the HEPA filter onto the front of the fan, and you’re done! Your very own DIY homemade air purifier.

The metal bar in the middle will stick through the filter a little bit. You could saw the metal bar off, but my tests show it doesn’t seem to make a difference. Or better yet, make yourself a fancier DIY air purifier by finding a fan without a metal bar in the front, like the DIY air purifier I ship through Smart Air.


Rear view of DIY fan air purifier

front view of HEPA attached to make DIY air purifier

#5 Admire your new DIY air purifier

Total cost for this DIY air filter: 166 RMB (US$27). Compare that to 8,000 RMB ($1,300) for the fancy purifiers here in Beijing. I now ship a simple fan and a filter with a simple upgrade that increases clean air output by 15% over my original design for 228RMB (US$37).


DIY 1.1 Air Purifier Filter HEPA


Your next question is probably, does this DIY air filter work? See a live test here, how well it works if we use a stronger fan the DIY Cannoncomparison tests with the big brands, and a 200-day HEPA longevity test.

P.S. Should the filter go on the back??

You might be wondering, “shouldn’t the HEPA go on the back of the fan?” I always thought the answer would be “it works just as well both ways,” but I put it to the test, and the results surprised me. Click here to read more on the counter-intuitive results on filter placement!

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Hi there. I have done a similar thing ihere in Chaing Mai but instead of using a Hepa filter I used Filtrete air con paper made by the company 3m. Do you think this would also be an effective way of cleaning the air?

Yes, you can use the 3M AC filters for your air conditioning! We have actually tested this, but are yet to write up a report on it. What we found was that using the paper on air conditioners was effective at removing around 80% of PM2.5 in a small 10sqm room. However the effectiveness will depend greatly on how powerful your AC is and how often you change the filter paper.

Andy Apolloni

where in chiang mai did you get the filter paper? Everyone of my mates leaves this time of year because of the smog. I will be returning later in the year but i want to prepare for next year


Are the HEPA filters washable? Or do you have to replace the filter after 6 months or so?

Good question Glenn! We wanted to know the answer to that, so we ran tests and published the results. Read about whether or not you can wash HEPA filters here.


I really enjoy that you are sharing technical proof in the article. I do a lot of drywall (gypsum) wall work and have been doing this same thing for almost 20 years. I use the 20in box fans that are sold everywhere (in America) for $25 or less and furnace air filters $7-20 depending on quality and vendor. This allows work to be done in single rooms with the doors closed keeping the dust from invading the rest of the home. For $30-40 (US) I have great air cleaning comparable to commercial units costing $130-400. I also get very affordable… Read more »

Gayathri Saju

WOW That is awesome marvellous and outstanding. I do prefer this site for many diys!

Ying Li

I am from Malaysia.
In the consideration of expensive international shipping cost for a cannon fan, I would prefer to purchase the fan locally. Please advise me if I could use an
exhaust fan with the air flow rate at 830m3/hour, using both HEPA filter and activated carbon filter for purifying my newly renovated house?


Do you have your filters and such available for purchase in North America? I’ve enjoyed navigating around your website! Thank you for all the work and publishing the information.

Hey Craig, glad you’ve found the info on our site useful! Right now we don’t have outlets in North America, although we can ship to individuals through our online store (although be warned: shipping is often more than the cost of the filter itself!)

We’re always looking for distributors to spread our low-cost solutions and the knowledge that clean air doesn’t need to cost an arm and a leg, and North America is definitely within our sites if you know anybody who might want to help out!

Terrific! Many thanks for sharing your work.

Woah, Your Post is very usesful, I’m From VietNam, I will try to make it

[…] Amazing! A “miraculous purifier” that removes PM 2.5 and formaldehyde in just 30 seconds. And all that for far cheaper than regular purifiers and even cheaper than building your own purifier. […]