The MSDS mentions this manufactured product as protected and when used under ambient conditions poses no health hazard.
However, if the product is heated beyond 200 or if it catches fire, then, the major constituent asphalt (bitumen) will emanate slightly toxic fumes.
I've discussed via IM to about 4 others that have used a similar product, one person even used 90lb felt, and the only thing heard once in awhile at very loud levels was his dual svs subs. Only time will tell, not to worried about it.
