It's a single-ply membrane (either EPDM or TPO) with an approximatley 1-1/4" insulation board between the membrane and the corrugated metal roof deck. Have not been able to find MSDS on either of those products. Apparently they are flammable but are most often treated with fire retardants. Store personnel on the scene had no clue regarding the roofing material. I'm in the public sector. We are expected to generate our report by the end of the shift so this report is already "in the books". Just following up for my own edification. Thanks for your input!