The term was recently coined to identify the residual tobacco smoke contamination that remains after the cigarette is extinguished and second-hand smoke has cleared from the air.

Third-hand smoke refers to residual tobacco smoke contamination that lingers on surfaces, dust, and fabrics after a cigarette is extinguished and second-hand smoke clears from the air. It can persist for months and react with other chemicals to form new toxic compounds, making it a distinct health hazard beyond firsthand and secondhand smoke.