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A small DIY air purifier

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Re: A small DIY air purifier

#81

Post by cosmolev »

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…

+1. Together with a test in the same environment without a purifier at all. PM count drops down to almost 0 in a room with closed windows with a breathing person inside. Lungs of a person act as a perfect purifier.

Re: A small DIY air purifier

#82

Post by aj7 »

post_break wrote: post #67
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…

If you want this to actually work, you take a box fan, and 2 filters. You make a triangle and then some cardboard on the top and bottom to fill the gap. This increases surface area and reduces the stress on the fan due to pressure drop. Slapping a filter directly on to the box fan is going to kill the fan very quickly. https://i.imgur.com/SX1RloH.jpg

Right. And in general, duct tape and popsicle sticks take care if that housing.

Re: A small DIY air purifier

#83

Post by SamBam »

This basically looks like a mini Shop-Vac.

If you own a Shop-Vac (a wet-dry vacuum, generically), could you just turn it on without the hose? It would draw much more power, but presumably would work much quicker, and so may end up being more efficient.

Re: A small DIY air purifier

#84

Post by apta »

kevinconroy wrote: post #68
fareesh wrote: post #62

Earlier quoted context omitted.

Would something like this this work sufficiently well to capture airborne fur/dander from a tabby cat? Or will there be a vastly different outcome from an expensive one?

Yes! We have two box fans with HEPA filters in our bedroom to combat the cat fur/dander. It's made a world of difference. You can see it working as the filter captures everything. Have to change them monthly... but so worth it. #YMMV #YouCatsMayVary

Do you strap them to the front or the rear of the fan? Doesn't having them on the front (i.e. where the air blows out) mean that the fan will get dirty since it's sucking the air in?

Re: A small DIY air purifier

#85

Post by yboris »

chewz wrote: post #23

This seems like useless toy. You should be aiming for something larger that would work for an apartment. [1] https://youtu.be/kH5APw_SLUU [2] https://youtu.be/8Hkdpx-59kk There is thousand vidoes on Youtube on how to DYI one.

Thank you for sharing these two videos! I really like the 1st one with the air-quality-measuring-instrument.

Re: A small DIY air purifier

#86

Post by Raphmedia »

jwr wrote: post #12
wiradikusuma wrote: post #7

Do air purifiers really work? I always have impression they're just sham, or at least placebo.

Yes, they definitely do, although to a various degree of effectiveness. If you get a Xiaomi Mi Air 2, for example, it will be very effective. If you get a Dyson fanless thing, not so much. In general, there is no escaping physics: you need to move a large quantity of air through something that traps dust particles. The low-tech solution of a fan and a HEPA filter is a very good one, but I would suggest getting a filt…

> If you get a Dyson fanless thing, not so much.

Any sources on that? I have one and I swear by it. They have a glass HEPA filter and a carbon filter. I'm not quite sure how much air it moves but it's enough to scrub the air of my two floors apartment when someone smokes indoor. It's not really fanless per-se, it's a turbine in the base. You are simply moving the blades down into the base and away from the output area.

Re: A small DIY air purifier

#87

Post by nathancahill »

opencl wrote: post #70
post_break wrote: post #67

Earlier quoted context omitted.

If you want this to actually work, you take a box fan, and 2 filters. You make a triangle and then some cardboard on the top and bottom to fill the gap. This increases surface area and reduces the stress on the fan due to pressure drop. Slapping a filter directly on to the box fan is going to kill the fan very quickly. https://i.imgur.com/SX1RloH.jpg

I ran a few cheap box fans with filters directly over them for several years and none of them failed, I have heard this claim a lot but it seems overstated. The triangle setup will significantly increase the airflow and thus the effectiveness of filtration though.

I've done this too for years and no issues.

Re: A small DIY air purifier

#88

Post by OJFord »

cosmolev wrote: post #81
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…

+1. Together with a test in the same environment without a purifier at all. PM count drops down to almost 0 in a room with closed windows with a breathing person inside. Lungs of a person act as a perfect purifier.

> Lungs of a person act as a perfect purifier.

Is that good?

I mean, of course it's good that PM doesn't just pass straight into our bloodstream, but isn't our lungs doing the purifying exactly the thing that people try to avoid with mechanical air purifiers?

Re: A small DIY air purifier

#89

Post by OJFord »

mhd wrote: post #8
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…

I don't know why, but I love the fact that someone is selling filters strapped to fans on a reasonably glossy and well-made page.

It does kind of look like a joke doesn't it? A demo/how-to masquerading as a shop page.

Re: A small DIY air purifier

#90

Post by trehalose »

loldot_ wrote: post #60

I don't know how effective they are compared to these devices, but I much prefer to keep plants with air purifying qualities. NASA did a study on a variety of air purifying plants in 1989: https://ntrs.nasa.gov/search.jsp?R=19930073077

That's an interesting study, but it appears to only study the plants' ability to filter out a few VOCs. HEPA filters won't help with those (you need an activated charcoal filter for that... or plants, I guess?), but they will help with particulates, and I'm not sure plants will do anything for those.
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