Levels of smoke-related chemicals rise sharply during age-restricted action films, but less so during a children’s flick.

Even in a non-smoking cinema, filmgoers can be exposed to hazardous tobacco-related pollutants, which waft off the clothing and bodies of smokers in the audience.

Third-hand smoke is the hazardous pollution from cigarettes that has settled onto various surfaces and is then re-released into the air. To understand how third-hand smoke can be transported into non-smoking environments, Drew Gentner at Yale University in New Haven, Connecticut, and his colleagues measured the levels of a wide range of gases and particles in a cinema in Mainz, Germany, over a four-day period.

The researchers observed that the concentrations of 35 tobacco-related volatile organic compounds (VOCs), including carcinogens such as benzene, spiked at the start of film showings. These concentrations varied with both time of day and film rating; VOC emissions were minor during a family-friendly film, but were much higher during age-restricted action films.

Tobacco-related VOCs also accumulated in the cinema during each day of the study and over the course of the weekend. These compounds could build up more quickly and persist for longer in smaller spaces such as bars, trains and homes than in cinemas, the researchers say.