Comment by dekhn
15 hours ago
I bought a large soldering iron air purifier and it turns out to be great; it has a continuious speed selector, easy to replace filters, and very pleasant spectrum. I like it better than the air conditioner, which cycles on and off noisily.
One of the best air purifiers you can get (linked in the above writeup) uses PC fans and a custom controller where you can control the speed/volume: https://housefresh.com/best-air-purifiers-we-tested/#2-best-...
Why is this so expensive? It's literally 4 PC fans and some plastic trays? I presume you bring your own filters.
You can make your own to save money, I made this project for example. I paired it with an Air-1 sensor and home assistant to ramp up and down the downs in real time according to the live air quality readings.
https://makerworld.com/en/models/2470181-nukit-tempest-euro-...
Filters are included, as well as high quality fans, AC/DC converter and speed controller, and the portable/collapsible enclosure. It's really not that expensive vs trying to put together the parts yourself, and it's tested to work very well compared to other more expensive filters.
Those fans will not have sufficient static pressure to be useful. These makeshift purifiers may be great in a pinch (wildfire season and stores are all out), but far from the best.
This is indeed the "conventional wisdom," but if you do the math it turns out this is incorrect.
The trick is to use high-airflow MERV 13 filters (ideally 3M 1900, which has high pleat count and low resistance) instead of high-resistance HEPA filters, so axial PC fans can generate enough pressure.
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The linked PC-fan purifier has been tested and shown to purify air faster than the conventional alternatives, and are not makeshift, so I'm not sure what you are referring to.
From the specs it looks like they are probably closer to higher-static-pressure server fans, the CADR is a few hundred CFM and it pulls 30+ watts. And as with many of these designs, you can compensate for low pressure performance by increasing filter surface area... the greater the surface area the lower the pressure drop. Of course, the problem with this is you are just spending more money on filters, which is the expensive part.
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