This is a sub-category of deaths due to suicide, and relates to self-poisoning by exposure to gases and vapours, including carbon monoxide and motor vehicle exhaust gas. It also includes cases where intent is undetermined but suicide is often a possibility.

The rates are noticeably low for this method of suicide in areas where many people do not own cars, such as in London. The rates are higher where households own several cars – and where more people have garages.

A common method of suicide that falls into this category is self-asphyxiation using car exhaust fumes. This is a method of suicide traditionally favoured by young and middle-aged males (Amos et al, 2001) and is duly reflected in the age–sex bar chart. The introduction of catalytic converters (that remove carbon monoxide) to cars in the 1990s had the effect of reducing the number of deaths from this cause. However, Amos et al (2001) reported evidence of a compensatory rise in rates of hanging among young and middle-aged men (see Map 34).

Similarly, when the domestic gas supply was switched from coal gas to natural gas (which does not contain carbon monoxide) there was a significant drop in the suicide rate using this method. That change occurred before the data that are shown here were collated.

Amos, T., Appleby, L. and K. Kiernan (2001) ‘Changes in rates of suicide by car exhaust asphyxiation in England and Wales’, Psychological Medicine, no 31, pp 935-9.

Poet Sylvia Plath and pathologist Sir Bernard Silsbury died from this cause.