Comment: I need an estimate for testing our air, I believe it is from the heating and ventilation system. We have a black film on the walls. I am not a smoker so that is not what is on the walls. My landlords whole theory on this is it is candle soot. This is a pretty good size two bedroom apt. My security deposit is being held until we find out what the black film on the walls is from. I have been in the home maybe a total of 4 months out of the entire year.