@jeff1047 Jeff, this is great information. I like the Corsi-Rosenthal box. It's such a simple idea. We do use the furnace filters with the highest level of particulate filtration available. I also used to work in a research lab doing histology work, and the professor was very fussy about a dust free work space because if dust got into a microscope slide, an image of that tissue could not be published. This was long before digital photography in the days of film and darkrooms. He was wrapping the air registers with filmy fabric to catch dust.

During the beginning of Covid, when people were sewing masks because none could be purchased and limited supplies were needed by hospitals, I was looking up how well fabrics would filter smaller particles like an N95 mask or respirator. I read that denim fabric does pretty well, and I tried making a mask from it. I do keep a respirator with me when driving for those times when my lungs reactive to outside air. I also have run my Foust air filter in the car, but it is big and bulky and can fall over with starts and stops. They do also make a small model for vehicles.