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A small DIY air purifier

github.com

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Re: A small DIY air purifier

#21

Post by 0-_-0 »

lmilcin wrote: post #13

Air quality test before and after or it doesn't work. I am very suspicious with regards to air purifiers. Have you ever seen real HEPA filter? It is thick and it is quite difficult to push air through it. I can't imagine small PC fan that is designed to push air through UNOBSTRUCTED space will make any significant flow of air. I have spent some time with the guys who build PCs and who know great deal about fans and o…

> Because they are designed to be quiet and still provide good flow of air they produce almost no pressure differential to speak of and the flow can be halved by a wire mesh that is a bit too dense

There are high static pressure fans which address this problem, specifically designed to work with pressure differential, usually used to blow air through radiators for water cooling. The fan linked in the github page (Noctua NF-F12, the "cheap fan" in the picture) is such a fan, it provides a static pressure of 7.63 mmH2O, which is very high.

Edit: you can get regular-sized 12cm pc fans that need 48 watts and rotate at 7160rpm, move 7.160 m^3/min air at 35.877 mmH2O static pressure:

https://www.frozencpu.com/products/8147/fan-500/Delta_Mega_F...

Re: A small DIY air purifier

#22

Post by thehesiod »

kn100 wrote: post #6

This is a really cool project but frankly you can do it a lot cheaper. Find the cheapest box fan you can find, and find the cheapest HEPA filter you can, and strap the HEPA filter to the front. To improve air purification even futher, slap an activated carbon filter on the front too, and your air purifier now filters VoCs! For cheap Activated Carbon Filters, look into the kind used for Aquarium filters. They'll work…

know a way to get them to US reasonably? cost is like 10x when shipping to US :(

Re: A small DIY air purifier

#24

Post by clarry »

Speaking of air purifiers, does anyone have recommendations for one that is quiet and still effective?

I have a pair of Electrolux EAP300s, in small rooms.

Unfortunately on the lowest manual setting ("Quiet") they hardly do anything for air quality. And they're still louder than I like. I think they really optimized for cost; these devices feel very light and plasticy, the fan sounds cheap and has an uneven tone to it, and its speed keeps oscillating back and forth. The purifier itself is also not stable and it can make an annoying noise if placed on a surface that ends up vibrating along.

I also thought about DIYing one with noctua fans (which I know are quiet, and I have plenty of them in my PCs), but I suspect they're not going to be very effective.

Re: A small DIY air purifier

#25

Post by qpiox »

Zardoz84 wrote: post #20

I would say that there are electronic schemes and plans to build DIY ion air cleaners. They works nice to remove dust or tabacoo from air. Also, ozone air purifier make wonders to keep at bay smells and fats (wonderful to have on the kitchen), and kills bacterias, spores and fungus.

Ozone is harmful.

Re: A small DIY air purifier

#26

Post by adrianN »

ivanhoe wrote: post #18

if you don't mind a noise you could buy a 2nd hand vacuum cleaner with a built-in hepa or water filter (ideally also with adjustable speed to make it less noisy) and just let it run without a hose, sucking the air and pushing it through the filter...

If you don't mind the noise and wasting a kilowatt on something that can be done with two dozen watts.

Re: A small DIY air purifier

#28

Post by qpiox »

clarry wrote: post #24

Speaking of air purifiers, does anyone have recommendations for one that is quiet and still effective? I have a pair of Electrolux EAP300s, in small rooms. Unfortunately on the lowest manual setting ("Quiet") they hardly do anything for air quality. And they're still louder than I like. I think they really optimized for cost; these devices feel very light and plasticy, the fan sounds cheap and has an uneven tone to i…

It depends on what noise level is acceptable for you and the room size.

Out of 30 or so air purifiers available in shops here, of all the ones that are in the $100-500 category, the Winix P/U450 are able to push the largest amount of air under the constraint of HEPA filters are rated at which air speed they are most effective and how much pressure is needed. The ammount of pressure will only rise as the filter is saturated with dirt. You need a sufficiently powerful fan, and fans that are both powerful enough and quiet enough are very expensive.

Re: A small DIY air purifier

#29

Post by mrspuratic »

jwr wrote: post #10

I would suggest worrying much more about PM2.5 and getting a filter that does trap those particles. Many health problems are caused specifically by small particulate matter.

His statement "I'm not concerned with the ability of the device to remove PM2.5" comes across as dismissive - he's not concerned because he's using a HEPA filter health officials are recommending and therefore he trusts it. HEPA starts at 0.3μm ("PM0.3") particle size, which doesn't cover finer forms of elemental carbon (soot). "H13" is a minimum retention efficiency though, not a specific particle size or application.

Re: A small DIY air purifier

#30

Post by qpiox »

jwr wrote: post #10

I would suggest worrying much more about PM2.5 and getting a filter that does trap those particles. Many health problems are caused specifically by small particulate matter.

A true HEPA filter does capture PM2.5
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