Vaping refers to the act of inhaling and exhaling aerosol, often called vapor, produced by an electronic cigarette or similar device. These devices heat a liquid that usually contains nicotine, flavorings, and Secondhand Smoke and Electronic Cigarette Aerosol Resources US EPA Juul study shows secondhand vaping emissions are less toxic than cigarette smoke Vaping Around Babies How Secondhand Vapor Smoke Can Harm Kids