This room was off-limits to smokers, but its air contained surprising amounts of `thirdhand smoke`
(LA Times Clippers)

Pop quiz: If you sampled the air in an empty college classroom where smoking is not permitted, what is the last thing you´d expect to find? If you guessed `cigarette smoke,` you´re in good company. Peter DeCarlo, an air quality researcher at Drexel University in Philadelphia, would have agreed...