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
They're the ones who did the actual testing/measurements. I had a box fan attached to a single filter (for wildfire smoke) but was unaware of how inefficient it was.
just to follow your logic. lets say I invent car. Corsi and Rosenthal measure it to discover how more efficient it is compared to horse, and from that point it's known as their invention
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
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.
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
labs don't certify that mask is more effective per dollar compared to usual air filters.
hence extra research by Corsi and Rosenthal is needed. After they will do the measurements they can be declared as inventors of p100 masks, that will be known as Rosenthal-Corsi masks
The p100 masks are already certified so you can shop based on cost. Filters + fans are not certified so you have to know something more to understand what you are getting
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