There has been no determination of how long the harmful effects of secondhand smoke lingers in the air. Depending on a room's ventilation, the smell of tobacco smoke can linger for some time. If tobacco smoke is in the air, it can and does present potential health problems to all but particularly children. If secondhand smoke or the smell of secondhand smoke is not currently in the air but has been allowed to pass through clothing and furnishings, the odor may still be present and irritating. Exposure to secondhand smoke and/or its contaminants can cause or exacerbate (make worse) a wide range of adverse health effects, including cancer, respiratory infections, and asthma.
Read more about secondhand smoke at www.epa.gov/indoor-air-quality-iaq/secondhand-smoke-and-smoke-free-homes.