Passive smoking is defined as the involuntary inhalation of somebody else’s
tobacco smoke. Such secondhand tobacco smoke is a mixture of mainstream smoke
exhaled by active smokers and sidestream smoke released from the smouldering
tobacco and diluted with ambient air. Usually passive smoking occurs in a closed
environment, but it can also happen in an open environment. Passive smokers
inhale carcinogens, as well as other toxic components, that are present in
secondhand tobacco smoke.