Secondhand smoke, also known as environmental tobacco smoke, is a mixture of the smoke given off by the burning end of a cigarette, pipe or cigar and the smoke exhaled from the lungs of smokers. It is involuntarily inhaled by nonsmokers, lingers in the air hours after cigarettes have been extinguished and can cause or exacerbate a wide range of adverse health effects, including cancer, respiratory infections, and asthma.
Reconditioning of secondhand smoke, by separating smokers from nonsmokers, air cleaning technologies, and ventilating buildings cannot eliminate secondhand smoke exposure, stating that conventional air cleaning systems cannot remove all the poisons, toxins, gases, and particles found in secondhand smoke. Additionally, heating, ventilation, and air conditioning systems can distribute secondhand smoke throughout a building.