actually, ive looked closer and its a reddish stain... i think ill take the whole thing out of the hood and take a better look... it may have been a spill of chemicals. the person who sold it to me said it used to be part of a home laboratory... its a really nasty red stain
thx magnus! i might just have to try and see what happens... cirillonb: maybe its not water! i know it would be nasty to have some kind of mold or fungus growing on your HEPA lol (is that possible?)... maybe someone spilled some red chem over it hummm
by duct u mean the space around the blower at the back? luckily the blower looks great! i will scrub the whole thing
i was just asking cause HEPAs cost quite a bit in my country!
thx a lot for the help!