Noun phrase

Uncountable

Inhaling other people's tobacco smoke. The smoke is mainly "sidestream" smoke from the burning tip of cigarettes, cigars or pipe tobacco but there is also some "mainstream" smoke exhaled by smokers.
Passive smoking has acute irritant effects on the eyes, throat and respiratory tract, and can aggravate asthma. Recent research also suggests a possible connection with heart disease, and a possible association between heavy exposure to tobacco smoke of women during pregnancy and smaller babies.

What the law says
Under the Workplace (Health, Safety and Welfare) Regulations 1992, employers have to ensure that there are arrangements to protect non-smokers from discomfort caused by tobacco smoke only in rest rooms or rest areas. The HSE recommends that all employers should have a specific policy on smoking in the workplace, and that such policy be written down and generally available.

HSE (http://www.hse.gov.uk/pubns/indg63.pdf)

Health and Safet at Work Act etc. 1974; The Workplace (Health, Safety and Welfare) Regulations 1992

Second-hand smoke, Environmental tobacco smoke

= Fumo passivo