I've heard of first-hand smoke, the smoke you inhale directly from a tobacco product, and there's also second-hand smoke [1], the smoke that is given off by the burning end of a cigarette, pipe, or cigar. Now research [2] shows there's another type of smoke that can cause harm — third-hand smoke [3]. It's the invisible toxic gasses and particles that linger in the air, carpet, curtains, clothes, and hair long after a cigarette stops burning. Running a fan or opening a window don't get rid of third-hand smoke, and studies show that it poses the same cancer dangers and other health risks as first- and second-hand smoke. Watch the video below to hear more.

If you're interested in hearing more about third-hand smoke, check out this New York Times [5] article.