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Build a do-it-yourself home air purifier for about $25

uofmhealth.org

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Re: Build a do-it-yourself home air purifier for about $25

#121

Post by Kadin »

Dave_Rosenthal wrote: post #60

I spent the weekend researching, implementing, etc. air filtration as one of those affected by the CA fires. It was worth it! The first step for me was getting a device to measure particles in the air. The air quality index (AQI) is an aggregate score that is made up of contributions from several harmful components. Of these, the quantity (weight/volume) of small particles ( Directly measuring PM2.5 is very hard, req…

Did you put the filter on the intake or outflow side of the fan?

I have built one of these (20x20 furnace filter on a box fan) and always put the filter on the intake side of the fan. However it seems like people are placing the filters on the outflow side of the fan instead, for reasons that are not clear.

Since it seems like you did some measurements, do you have any idea whether it's preferable to have the filter on the intake or outflow side of the fan? (I note that in furnaces and other air handling equipment, filters are almost universally on the intake, not the outflow, side, presumably because this keeps dust out of the blower/heating mechanicals.)

Re: Build a do-it-yourself home air purifier for about $25

#122

Post by Kadin »

51lver wrote: post #21

I used a very thick (4") filter rated for smoke particles when the wildfires this year blew their smoke down to Seattle. The filter went from white to a very interesting shade of grey in 3 days. Wife was able to sleep again though, so it does work very well in my experience. (20x20 fan, filter on intake side)

Out of curiosity, where were you able to find the big 4" thick filters in the 20x20 size? I wasn't able to find anything other than the usual 0.75 thick furnace dust filters in 20x20 for a box fan.

Re: Build a do-it-yourself home air purifier for about $25

#123

Post by trisiak »

akeck wrote: post #89

Note that restricting airflow on a radial fan can cause the motor to heat up. Make sure you get a 20-inch fan with a fuse. To reduce heat, increase air flow by making a box with three filters and by using 2 inch deep filters. Also, when I built my three filter "box" last fall, I was able to order a set of three MERV-13 20x20x2 filters directly from Nordic Pure for less than what they cost on Amazon. Finally, to make…

Linked projects put the filters on the opposite side to what you're suggesting. Can you elaborate more on why do you think the filters should act on the air coming into the fan? Is it to increase heat dissipation of the motor?

Re: Build a do-it-yourself home air purifier for about $25

#124

Post by the_clarence »

electic wrote: post #110
benbojangles wrote: post #85

I built my own air purifier in 2016, living in London, I was living in a basement and was having breathing problems due to mould. My landlady was gaslighting me at the time, so I built the air purifier. It worked for a while but mould spores cling to the paper filter and eventually grow into the filter material. I think Dyson uses glass fiber filter to stop this problem. My filter helped a lot, but eventually I had s…

Woah, this is pretty scary. Thank you for sharing. How did you know it was mold that was in the air? Is there some sort of test kit that you can buy to test for this. Mold is pretty hard to detect because you can't really see it because it typically hides between the walls. Any advice appreciated.

You can notice black spots in your bathroom or other places where steam doesn't escape properly. I noticed it on my mattress also. I don't think I have any health issues because of that, it was 5 years ago, but it was rough.

Re: Build a do-it-yourself home air purifier for about $25

#125

Post by lilbobbytables »

I've been using a setup like this for the past year. I use a 4" think filter to reduce strain on the motor though (it's pleated, so a lot more surface area to pull air through than the thinner ones), the idea being reduced strain on the motor. I also stick a carbon pre-filter in front of it.

I get smoke wafting in from outside via window air conditioner - and I think my neighbor occasionally smokes in his room.

I'm planning to setup another to better cover my open floorplan.

Re: Build a do-it-yourself home air purifier for about $25

#126

Post by dmourati »

I have the ~$800 pro version early in the video. It's an IQAir. I bought it when I bought my house. We were refinishing the hardwood floors and have a small child. My goal was to knock down the VOCs to make the room safe for him prior to move in.

It runs 24/7 in my bedroom now. Huge improvement in sleep quality. I've only had to change one of the filters once for about $100 after 1.5 years of run time.

Re: Build a do-it-yourself home air purifier for about $25

#127

Post by lubujackson »

Kadin wrote: post #122
51lver wrote: post #21

I used a very thick (4") filter rated for smoke particles when the wildfires this year blew their smoke down to Seattle. The filter went from white to a very interesting shade of grey in 3 days. Wife was able to sleep again though, so it does work very well in my experience. (20x20 fan, filter on intake side)

Out of curiosity, where were you able to find the big 4" thick filters in the 20x20 size? I wasn't able to find anything other than the usual 0.75 thick furnace dust filters in 20x20 for a box fan.

I just bought a 4 pack from Amazon Prime Now in SF, YMMV.

Re: Build a do-it-yourself home air purifier for about $25

#128

Post by jakeogh »

These work excellent. I put a finer filter on the output. Clear difference in the pollen seasons, but I just let it run all year and swap the (visually clogged) input filter every few months. The FPR10 output filter lasts longer, but you gotta take a look at the side facing the fan to inspect it.

Also, consider adding output filters on any AC units (ducting etc). Even a "new" AC system can quickly become a source of particulates, or (way) worse.

Re: Build a do-it-yourself home air purifier for about $25

#129

Post by leon_sbt »

abalone wrote: post #82

Can we talk about Molekule? Their team and some SF tech community folks have been plugging it all over Twitter during this tragic wildfire crisis. But it seems like snake oil to me. It’s $800. Certainly for smoke particles it can’t possibly offer any more protection than a standard HEPA filter. But even for its claimed ability to nuke VOCs, the claim seems ridiculous. While particles can deterioriate under prolonged…

I have a hard time taking them seriously. Some of their "independent" lab results are from some USF lab. The same lab one of the co-founders was a director for... Go figure. Some please correct me if I'm wrong. Read the results in technology, and then read the bios of the people.

Re: Build a do-it-yourself home air purifier for about $25

#130

Post by peferron »

Important tip: if you set up an air purifier in your home, make sure to plug all drafts around your house: windows, doors, etc. Even a DIY purifier with small airflow can make your indoor air excellent if given enough time to do so and no leaks to fight against.

If you want to get some fresh air in your home, do not leave a window half-open all day long—instead, open all your windows at once to cycle the air as fast as possible, then close them again and let the purifier do its job. If you do that in the morning (ideally just before leaving, if you aren't staying home), you'll have great air quality through the entire evening and night.

Since we're on HN, I'll also mention a toy project I built a while back [0]. It uses a Raspberry Pi to read particulate matter sensor mesurements over serial link from a Dylos 1100 Pro, then pipes it into Redis and InfluxDB and ultimately Grafana for presentation. I've used it to track the air quality in my home in for the past year or so and it's pretty fun. In my case, cooking is usually the biggest contributor to poor indoor air quality!

[0] https://github.com/peferron/air-quality

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