Smoking, as we all know, is bad for you. We also know that inhaling other people’s smoke is nearly as unhealthy as lighting up on your own. Scientists are finding that just being in a car or building where people have been smoking is potentially bad news. When smoke curls off the lit end of a cigar or cigarette, it may seem to vanish. But the nicotine particles and many other chemicals in cigarette smoke don’t literally disappear. They soak into walls, floors, furniture, and even clothing. Beyond smelling bad, this so called third-hand smoke can react with common household chemicals to form toxic compounds.