Yeah, like Trev said it is'nt the best for good filtering. The thing is I have 3 dogs and 4 cats when originally constructed I needed something to keep junk out. Well I let it go and a few months passed and it never did begin to grow anything like mold, etc.. so I have left it on and it still does the job and I began dabbing the alcohol or H2O2(peroxide) to kill anything that might try to pass. On the other hand I should not recomend it because if you absolutely neede to keep out that stuff this setup could not be guaranteed. HEPA filters should be used for control over airborn particles and whatnot. What I got is probably luck.