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A small DIY air purifier

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Re: A small DIY air purifier

#71

Post by avian »

wlesieutre wrote: post #66
avian wrote: post #32

Earlier quoted context omitted.

> it provides a static pressure of 7.63 mmH2O If anyone else is wondering, that's about 0.8 mbar (roughly 8 ten-thousands of an atmosphere), or 80 Pa of over-pressure. To put this into perspective, my local atmospheric pressure varied about 2000 Pa in the last 48h due to weather changes.

Lemme go send my air intake through a time machine and as long as the weather keeps changing we can use that to drive air through a filter!

No need for a time machine (or being snarky - I did say it's just for comparison, didn't I? I think it does put the "very high pressure" into perspective)

That said, your time machine idea could be simply implemented with a large, airtight box. Simply put the filter over it and weather changes will push and pull air through the filter with two orders of magnitude more pressure than this little fan. Volume of filtered air will depend on the volume of the box though, so better get a large one.

Re: A small DIY air purifier

#72

Post by bipson »

sampo wrote: post #41

What do you think about air washers? In addition to air filters, they blow air over wet surfaces to both clean and humidify the air. Here is one from Phillips: https://www.youtube.com/watch?v=n3xC3qxVphw

I have one of those.

It does not "wash" the air. It has a HEPA-filter on the intake side before the humidifying cycle. So it is basically the same thing as all other examples on this comment page.

You can actually run it without water (which we do), then it does only filtration.

Don't buy this particular product. It is overprized and has dramatic production quality issues (we sent two back, amazon reviews indicate larger issues).

Re: A small DIY air purifier

#73

Post by yjftsjthsd-h »

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

Clarification: triangle goes on the in or out side of the fan?

Re: A small DIY air purifier

#74

Post by bipson »

grogenaut wrote: post #58

Is a filter or an ionizer better for smoke? https://hackaday.com/2020/01/12/diy-ionizer-clears-the-air-o...

At least some of them don't really work at all. https://www.youtube.com/watch?v=VM9CJZpqfpA

With something as simple and effective as HEPA-filters, it seems unreasonable to try other technologies.

Re: A small DIY air purifier

#75

Post by post_break »

yjftsjthsd-h wrote: post #73
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

Clarification: triangle goes on the in or out side of the fan?

Doesn't really matter as long as the filters are in the correct orientation. However it would be beneficial if the air is clean before it goes through the fan.

Re: A small DIY air purifier

#77

Post by post_break »

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 guess it depends on the quality of filter. If you're rocking a high merv filter for smoke the pressure drop can be significant.

Re: A small DIY air purifier

#78

Post by minikites »

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

You would need to live in an indoor rainforest (approximately 680 plants for a typical house) to see an effect on air quality, a spider plant in the corner isn't doing anything: https://www.youtube.com/watch?v=AmeiXikh0v8

Re: A small DIY air purifier

#79

Post by Eric_WVGG »

Eric_WVGG wrote: post #65
wiradikusuma wrote: post #7

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

I felt similarly, but I have a family member who is bed-bound, there’s some asbestos removal going on, so I decided to take the plunge. I can vouch for their ability to detect impure air. If I start cooking anything, it switches on within seconds. It’ll turn on within about three minutes of sweeping the floor. And if the detectors can turn on when the air is dirty, it stands to reason that they can tell when the air…

(A few minutes after posting this, morning rooftop construction started. Sounds of saws and drills buzzing, large objects and beams being dropped directly overhead. Air purifier just kicked into high gear. Yes, I’m definitely into this thing.)

https://thewirecutter.com/reviews/best-air-purifier/

Re: A small DIY air purifier

#80

Post by sfgweilr4f »

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

Hasn't that been partially debunked or at least conditions placed on how effective they are? I lost the article that reviewed it.
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