I have been searching all over the internet for someone that might have the same issue we are having in our bathroom. Our house was built in 1968 and the tub is quite possibly the original tub. Anyhow, it appears that a very glossy black sealant was poured into the open area of the foundation where the tub's trap is located. Its poured about 2 inches thick and is very solid. The chemical smell is somewhat similar to an asphalt sealant that you might use on your roof. Anyhow, when you open the tub access door, the smell about knocks you down. Its almost as bad with the access door taped shut. I've tried deoderizers with no luck. Does anyone have any suggestions? They'd be much appreciated.