I opened this package to immediately start using it. The petroleum-like smell was very strong. I'm just learning about toxic out-gassing of products so was concerned about this. I let it air out over a chair rail for 7 days. Still smelly. I washed it in suds and warm water. Still smelly. I suspect the rubber backing is a petroleum derivative. It is a few weeks later and I still can't use it for long periods. ... Wishing I hadn't tossed my old one ...