We are in the fire area with tons of smoke. I have hooked up some filters on a couple of box fans to work with the house air system to filter the smoke out of the house. They are doing a great job.
haven't used yet. i got them to give to neighbors and friends who don't have HEPA filter but can use the filter with a box fan to help keep their inside air clean when the smoky skies return here in the NW.