You know what would make for some good drywall? The waste materials from scrubbers on coal-fired power plants. That’s apparently what some Chinese manufacturers thought during the housing boom. When they leak and combine with the moisture on AC coils, the result is sulfuric acid, according to complaints by some Floridian homeowners. The acid dissolves the coils on the AC units and in some cases the units fail. Imagine what it does to your lungs.