Vaping e-liquids or smoking tobacco indoors can have substantial impacts on air quality. Potentially dangerous chemicals volatlized by high temperatures in the device or cigarette can be inhaled by others in a room ("second-hand exposure") or deposit on room surfaces to be evaporated and inhaled at a later time ("third-hand exposure"). These chemicals can be in either the gas or particle phase, depending on the history of the room temperature and emissions.
Vaping represents a signigicant unknown for chemical exposures, as both e-liquids and vaping device materials are continuously being redesigned to include new consituents. These materials can include heavy metals, plastics, oils, and flavorings with unknown health effects and high temperature dynamics. In addition, the temperatures reached by vaping devices vary significantly between different devices and user preferences.