Quote:
Originally Posted by oil pan 4
I made what I call a filter fan.
I taped a fairly cheap 20 inch square filter to a 20 inch box fan. It's better than nothing.
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For cleaning indoor air for health purposes this is perfectly fine. A MERV 11 or 13 filter will only pick up a fraction of sub micron particles, but since it's recirculating, it'll eventually trap a large portion of them.
For destroying viruses (and other pathogens), a UV-C lamp is probably more useful than a better filter.
The only issue with the box fan filter is that a box fan is meant for low pressure drop and has all that open area where back flow can occur. You can use a cardboard cutout to block off the edges and stand off the filter from the fan as a makeshift shroud to improve its performance.
For the purposes of avoiding exposure to the virus outside, you need true "HEPA" level filtration. I've been walking around with a P100 mask which supposedly catches >99.9% of viruses.