We all know that smoking is a dangerous habit and that secondhand smoke can also be hazardous to your health. But thirdhand smoke? Sounds like a joke.

It’s deadly serious.

Thirdhand smoke involves the toxic compounds from cigarette smoke that cling to the clothes even long after a smoker has taken a last drag. A study led by a Yale scientist found that large quantities of these compounds can be carried into nonsmoking environments.

Researchers went to the movies to see how the compounds were carried into nonsmoking environments. They used analytical instrumentation that can track numerous compounds in either gas or particle form. For a week, scientists took their measurements in a modern, well-ventilated movie theater.

A range of volatile organic compounds found in cigarette smoke that are known carcinogens spiked when audiences watching R-rated movies came into the theater. But in G-rated movies, the increase was far less dramatic, as those moviegoers were far younger and less likely to smoke.

And this wasn’t just a trivial dusting of compounds. The study found readings of gas emissions equated to being exposed to one to 10 cigarettes of secondhand smoke in an hour. The level of these compounds peaked while audiences were in the theater, but they did remain, at a decreased level, long after the movie ended. That’s because surfaces absorbed the contaminants.

You’re not going to avoid the danger just by avoiding going to the movies. As the scientists note, any indoor space, especially those that are small and cramped, will pose the same problem.

But if you’re going to the movies, seeing a G-rated movie is apparently a healthier option.