Secondhand smoke is a mixture of the smoke given off by the burning of tobacco products, such as cigarettes, cigars or pipes and the smoke exhaled by smokers. Secondhand smoke is also called environmental tobacco smoke (ETS). Exposure to secondhand smoke is sometimes called involuntary or passive smoking. Secondhand smoke, classified by EPA as a Group A carcinogen, contains more than 7,000 substances. Secondhand smoke exposure commonly occurs indoors, particularly in homes and cars. Secondhand smoke can move between rooms of a home and between apartment units. Opening a window or increasing ventilation in a home or car is not protective from secondhand smoke.
The health effects of secondhand smoke on nonsmoking adults and children are harmful and numerous. Secondhand smoke causes cardiovascular disease (heart disease and stroke), lung cancer, sudden infant death syndrome, more frequent and severe asthma attacks, and other serious health problems. Several landmark health assessments regarding secondhand smoke have been conducted.
Key findings:
Eliminating secondhand smoke in the indoor environment will reduce its harmful health effects, improve the indoor air quality and the comfort or health of occupants. Secondhand smoke exposure can be reduced through mandated or voluntary smoke-free policy implementation. Some workplaces and enclosed public spaces such as bars and restaurants are smoke-free by law. People can establish and enforce smoke-free rules in their own homes and cars. For multifamily housing, smoke-free policy implementation could be mandatory or voluntary, depending on the type of property and location (e.g., ownership and jurisdiction).
Come from https://www.epa.gov/indoor-air-quality-iaq/secondhand-smoke-and-smoke-free-homes