not that much of innovation.

i build one like this back in 2018 during california fires. used it mostly in garage for filtering air when i work on "things". decommissioned it last week.

i guess i am not the only one who came up with this idea prior to covid as this is pretty obvious

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tehjoker 2 hours ago | parent [-]

i did think the 4-sided design using the cardboard box as a base was very efficient. one of the contributions here was Corsi and Rosenthal did this in a lab and reported particulate counts, flow rates, and energy usage. So there was some kind of intellectual contribution to broaden adoption by giving it more of an imprimatur of quality

other refinements were using a shroud to prevent back flow

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tguvot 2 hours ago | parent [-]

back in 2018, during fires, when air filters were unobtanium, on bayarea subreddits (and probably here) were floating a lot of posts of DIY filter made from box fan + hvac filters. plenty of people also posted particulate count reduction charts.

you don't need a lab to figure out that replacing 1" filter with 4" filter and even better arranging multiple filters in a box will improve flow rates and filtration (especially for box fans that not really designed for static pressure)

corsi&rosental work, imho, is equivalent to lab work reporting that you can move more water through 10" pipe than through 1" pipe.

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tehjoker 2 hours ago | parent [-]

I can see that argument, but I think what they contributed was that there's something approaching a cost-optimal design. they reported that the 4-sided design with box fan had higher CADR than many if not all commercially available filters though it often used more power and was louder, so the filtration per dollar was very good

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tguvot an hour ago | parent [-]

p100 masks will have optimal filtration on HEPA level per dollar.

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tehjoker an hour ago | parent [-]

can't argue with that

	▲	tguvot an hour ago \| parent [-]
		I think we should wait for Corsi and Rosenthal lab work on this topic