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’ve tested the heck out of this DIY air purifier! The data shows it works, even for tiny PM2.5 particles, compared to the big brands, with a control test room, over 200 days, and in a completely controlled test environment). But here I’ll explain how I made it.

 

DIY Purifier Test AQI PM2.5

 

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. Here are a few other important questions:

  1. Filters: What combination of filters do I need to protect against everything?
  2. Stronger fan: Tests with the DIY Cannon
  3. How can I test it: Comparison tests of common air quality monitors

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.


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Mira Mihajlovic

Hi. Will your fan plug into Australian powerpoints?

Hi Mira, the plug on our DIY fan is not the same as Australia’s plug type, but with a simple adapter (similar to a travel adapter) you will be able to use the fan in Australia!

shriram krishnamurthy

hello, I have purchased a diy1.1 air purifier. Which side of the hepa filter should face the fan?

Britt Labutte

Hi! I’m in ACT Australia and currently due to extreme conditions, hundreds of fires are burning 1-3 hrs away. This is blanketing our city for weeks.
Needing to attempt to make this amazing alternative as I cannot breath easy in my smokey apartment with my children.
My question is, after I purchase my fan and hepa-filter, can I also attatach a carbon filter as well as 2x general filters to the one machine? I would be very grateful to know exactly the right combination and order (if there is one) please…so that all the ‘bad’ is captured effectively.
Thank you so much!

ethel

Hey Britt, can’t imagine what you and your family are going through in Australia because of the fires!
To answer your question, there can only be 1 filter attached to the fan at each time — either a HEPA or a carbon filter. If you attach more than 1 filter, it will not be effective because a fan’s strength isn’t enough to support both.

Dejan

Hye Ethel, just quick question: what depth of HEPA filter should be? I have options 20mm, 25mm, 30mm, 35mm?

Kate

Hi Britt I am in Australia experiencing the fire conditions in Canberra; where did you buy your HEPA filter?

Kate Bolas

Hi Britt I am in the ACT also where did you get your HEPA filter?
Kate

Thanks for this! I was inspired to build my own. Q: do you recommend combining HEPA and activated carbon filters with a regular box fan, or would that put too much strain on the motor?

I’m running it with both at the moment, but I don’t even know if it’s pulling the air through at sufficient volume to be effective, since I can’t feel the air flow pushing out the front.

Thanks!

ethel

Hey Rory, you can combine a HEPA and carbon filter on a box fan but the best way to make sure it is effective is to get an air quality monitor!

Muhammad Khizar

Hi, this maybe a silly question. I just made a DIY air purifier similar to instructions here. How much of air flow should we be able to feel at the front of the HEPA filter ? Little or none at all as I am getting almost none.

Hey Muhammad! This is a very common question for DIY air purifiers. Even if you can’t feel a lot of air coming out of your DIY, it doesn’t mean it’s not working. With the original DIY that Tom made, it also felt like very little air was coming out, however tests proved it to be effective. Check out this video of Tom showing this: https://www.youtube.com/watch?v=JpfpZofUzNo&t=7s To ensure you’re getting the maximum air possible out of the purifier, make sure there’s a good seal between the fan and the filter, and that no air is leaking out of the back of… Read more »

davis.c.fay

Hello! I had a similar problem to Muhammad’s – little to no air flow out of the front of the filter and significant flow out of the back of the fan (even after taping up all of the side vents in this particular desk fan.

What do you recommend to correct for this? I’m in the USA, so I don’t believe I have affordable access to the same fan listed in the instructions in this blog post.

If you’re in the USA, then you’re in luck! I suggest you get yourself a box fan and a large furnace filter. These fans are extremely powerful and very affordable in the US. They should be a great option for you!