This year we moved up to a 2x5 boiler and the boys set it on skids atop plywood instead of the recommended concrete. We started our first boil with it yesterday. Within the first 30 minutes the hot metal started to burn the plywood, which really stinks as the glues off-gased. Their solution, although well intended, was to put cement board between the plywood and base of the evaporator. That too started to react to the extreme heat, causing the styrofoam beads (polystyrene) and chemical binders in the cement board to melt and off-gas quite intensely. The off-gassing and melting continued for the 5 hour duration of the boil. My opinion is to err on the side of caution and dump the batch. The offensive material has been replaced with concrete. My question to the forum is this. To what degree do airborne contaminants, such as diesel fumes and burning polystyrene and other hazardous substances in the boiling environment affect the taste and, possibly health quality of the finished product?