I am not even sure we should be using that foam in the first place. Some of it is pretty nasty when it burns. In my wife's typical 2500-3000 sq/ft house they would shoot 6 or 7 cans of that foam, based on the dead soldiers I saw laying around. The MSDS for "Great Stuff" says combustion products include but are not limited to oxides of nitrogen,isocyanates, hydrogen cyanide, CO and CO2.
