My fan ass’y mounts high on a wall (bottom at ≥ 80” from the floor per ADA, & the filter ass’y plus ceiling clearance takes about 33” above that, so ceiling ≥ 9’5” (many rooms are higher). But a mod with filter ass’y horizontal would work for 8’ ceilings. See ALT for concept.

The filter ass’y is very light, weighing little more than the 4 filters. The foam frame is reuable & it should be easy to replace filters at desk level and drop in place from a ladder, or even using a T-shaped pole while standing on the floor. See ALTs for more comments.

So I isolated the fans on closed foam weather stripping, 1/8” thick x 1/2” wide on edge. The fan rests on the edge of the foam, which rests on a new fan box base. The foam is held to the fan with electrical tape and to the base with double-sided woodworkers tape. See ALTs!

I measured noise, like CADR, with the 8 fans bolted to the underside of a shelf. Turned it on 6 times each V, letting it spin up for a minute ‘til pretty stable. About 46 dBA at 12V, but a bit different each time, especially at 9-11V. I suspected fan-fan interaction. See ALT.

I feel pretty good about measurements. I tested CADR in a 412.8 cubic foot bathroom, filled with nebulized NaCl solution, and mixed with a small fan. I used a Sensirion SPS30 Particle Counter, controlled by an ESP32 μcontroller, streaming into μSoft Excel. See ALT 4 more stuff.

I’m hoping somebody will figure out how to mass-produce a unit like this. Improve it. Surround it with an attractive perforated metal or plastic cover. Integrate it with a control box & timer on the wall below it. Now you know what kind of performance to expect. Check ALT.

Configuration is important. Warm human aerosol rises toward the ceiling. The idea is to scavenge warm, dirty air from the ceiling, filter it, & blast it down along the wall, where it can spread out over the floor & convect back up past the occupants’ faces. See ALT for more.

Finally! I built & tested an open-source concept model air purifier that should be good for schools. Lots of air (CADR > 420 CFM), quiet (<45 dBA), uses <9 W, and ‘cause it’s wall-mounted & down-blowing, it moves air in the right direction & takes up no floor space. Always check my ALTs🧵⬇️

That clean-air-in-at-the-bottom worked well in theaters, too. I'm working on an open-source wall mounted purifier reference design for classrooms with high ceilings, that scavenges warm air high, cleans it and blows it down the wall. Stay tuned.

Here's a notional diagram showing warm upward flow from occupants of a classroom and forced downward flow of filtered air. I'm hoping to have a long thread about my reference design in a couple weeks. A ceiling fan in the middle, pulling up, could only help.

Here's a preview of an open-source concept model for an air purifier that I think would be good for schools. It’s wall-mounted & down-blowing, but requires ceilings over 9'. 426 CFM CADR @12V, but I'm still checking the noise before publishing details. Maybe a couple weeks. See ALT for info.