Fuel gases can cause asphyxiation. This occurs when the fuel gas builds up within the dwelling, displacing the air to such an extent that the occupants are unable to obtain sufficient oxygen to breathe.
The critical oxygen level resulting in asphyxiation is 14% (normal levels being around 21%).
The number of fatalities varies from year to year and may be anything from less than 10 to around 40.
Very young children (those aged under 5 years) are most likely to suffer injury as a result of exposure to uncombusted fuel gas.
Elderly persons, aged 60 years or more, are also vulnerable because, although they are the least likely to be involved in such an accident, the proportion of fatalities is comparatively high.
Pregnant women are also vulnerable.
(Note: Poisonings associated with incomplete combustion of gas and the spilling back of combustion products into a dwelling are covered under Carbon Monoxide Risk, and explosions from gas leakages are covered by Explosions Risk.)