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A small DIY air purifier

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Re: A small DIY air purifier

#131

Post by frank2 »

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…

One thing to keep in mind is that an air purifier with a squirrel-cage fan (the kind of fan needed to pull enough air through a HEPA filter) makes a very pleasant sound that is good for masking, e.g., banging noises from neighboring apartments. I regularly run mine just to mask noise. So being loud can be considered a feature.

Re: A small DIY air purifier

#132

Post by logfromblammo »

jbob2000 wrote: post #109
logfromblammo wrote: post #108

Please don't use an iPhone X "for scale". The dual-ruled calipers used in the next photo would be an acceptable substitute for just using a plain old ruler.

Most people know what an iPhone X (or similar device) feels like. Not many people have held calipers (or remember what holding them feels like) and not many people can put into context what a marking on a ruler actually means. For a quick scale judgment, a smartphone is perfect. It's not supposed to be precise.

I respectfully disagree. Smartphones do not come in a single standard size. Using them as comparisons will end up with the same problem as using coins or banknotes--it is only helpful for those already familiar with the specific comparison item.

A "for scale" comparison is most useful with a metric-scale ruler. Metric lengths are standard worldwide. Including an inch-scale ruler may help US-based persons. The calipers were useful inasmuch as they had a metric length scale etched into them--a ruler with extra bits.

By your argument, it is acceptable to report large lengths or areas in multiples of US football fields, volumes as multiples of Olympic-size swimming pools, or database sizes in multiples of the entire literary content of the US Library of Congress. Journalists do this frequently, and every time, it drives me absolutely bonkers (an aggravation level equivalent to 3 rush-hour traffic jams).

Re: A small DIY air purifier

#133

Post by djannzjkzxn »

lotsofpulp wrote: post #119
sl1ck731 wrote: post #98

Earlier quoted context omitted.

I would assume the majority of people (in the US, anyway) are already filtering their air enough through their central air to make any additional "room-sized" filtering negligible. Similarly they make some very dense HVAC filters if standard ones aren't catching the level of particles you need, so I'm not sure what the purpose of these filter-fan things are for most people.

>Similarly they make some very dense HVAC filters if standard ones aren't catching the level of particles you need, so I'm not sure what the purpose of these filter-fan things are for most people. These are a scam, especially all those 3M filtrete ones. Air handlers in homes and most other HVAC applications are not made to also serve as tiny particulate filters, so it will make the whole HVAC system slow or even stop…

I believe you that the HVAC isn’t designed for such a filter. But a few months back my home was in the path of smoke from some wildfires. The AQI went from 200 to 0 after I installed a filter and ran the house fan for an hour. Also, the furnace doesn’t have to work very hard here because of the mild climate, so I never have much of a heat bill anyway. It would be a bummer if the furnace died because of it running out of spec, but I’m skeptical that the risk-adjusted cost of that is higher than the cost of standalone filtration units.

Re: A small DIY air purifier

#134

Post by overcast »

toastal wrote: post #100

I'm in Bangkok right now which is having a smog issue right now due to pollution and burning in the rice fields across the country. It's a shame that we're buying/making air filters instead of working on policy and cleaner methods of doing work--so now the poor and the wildlife can't afford to have clean air.

There are cleaner methods, stop taking the easy route and burning everything down.

Re: A small DIY air purifier

#135

Post by lotsofpulp »

djannzjkzxn wrote: post #133
lotsofpulp wrote: post #119

Earlier quoted context omitted.

>Similarly they make some very dense HVAC filters if standard ones aren't catching the level of particles you need, so I'm not sure what the purpose of these filter-fan things are for most people. These are a scam, especially all those 3M filtrete ones. Air handlers in homes and most other HVAC applications are not made to also serve as tiny particulate filters, so it will make the whole HVAC system slow or even stop…

I believe you that the HVAC isn’t designed for such a filter. But a few months back my home was in the path of smoke from some wildfires. The AQI went from 200 to 0 after I installed a filter and ran the house fan for an hour. Also, the furnace doesn’t have to work very hard here because of the mild climate, so I never have much of a heat bill anyway. It would be a bummer if the furnace died because of it running out…

This page has a decent explanation of the problem:

https://www.pvhvac.com/blog/whats-the-best-air-filter-for-yo...

All the commercial HVAC technicians I speak to say to use the cheapest non fancy filters if your goal is to maximize life of the HVAC system, but I'm sure it all depends on everyone's specific system and how the return is and whatnot.

Re: A small DIY air purifier

#136

Post by Eric_WVGG »

driverdan wrote: post #104
Eric_WVGG wrote: post #65

Earlier quoted context omitted.

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…

Being able to detect particulates in the air isn't what's important. You need to know if it's actually improving the air quality.

If you're referring to "air quality" in the form of particulates… it does turn off after a while. 15-30 minutes after cooking, one or two after sweeping, etc. Presumably it's triggered by no longer detecting particulates in the air, one would have to be fairly conspiracy-minded to suggest that it's working on some kind of timer (and can tell the difference between dust-timeouts and gas range waste timeouts)… I figured this was too obvious to point out, even given the sort of pedantry we get around here.

If you're referring to some quality of the air beyond particulates… well that's not what a HEPA is even for, is it? I could be mistaken.

Re: A small DIY air purifier

#137

Post by asah »

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…

Can confirm: did this when the wildfires hit SF a couple years ago, and it really worked!!

My "measurement" was my lungs when working from home: coughing before, no coughing after. Filters turned black.

Re: A small DIY air purifier

#138

Post by dublinben »

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…

Here's a video from the University of Michigan showing just how effective these cheap DIY air filters can be: https://www.youtube.com/watch?v=kH5APw_SLUU

Re: A small DIY air purifier

#139

Post by UnFleshedOne »

marcinzm wrote: post #50
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…

This may or may not work, cheap box fans aren't designed to push/pull air through obstructions (ie: low static pressure) and HEPA filters are giant obstructions. So instead of the air going through the filter it'll go through gaps, around the edges of the blades, etc. I used a cheap box fan for some DIY ventilation and the loss in airflow is massive after filter and ducting.

I used a cheap box fan and a furnace filter held simply by pressure differential.

Flow drops a lot, but it still works. Filter was dirty after some time. It was hilariously undersized for my purpose (serious belt-sander action leveling sub-floors), but air does move.

Re: A small DIY air purifier

#140

Post by cwkoss »

I've always wondered if you could essentially hook a blower up to a bong to filter particulates out of the air using water. Would be much cheaper to replace the 'filter', but I suspect it wouldn't filter as well. Seems like it could be an interesting tradeoff though.
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