AirBag

An increasing number of automobiles are equipped with airbags that rapidly inflate on collision, before car occupants can be thrown forward after impact. The chemistry principle involved in the inflation process involves a controlled chemical explosion that produces a large volume of gas (which inflates the bag).

Nitrogen gas (N2) is the inflatant in most airbags. Airbags are activated when an impact causes a steel ball to compress a spring and electrically ignite a detonator cap, which in turn, causes sodium azide (NaN3) to decompose, forming nitrogen gas and metallic sodium. (100g of NaN3 produces 56L of Ns gas at 25 celsius.) The sodium metal produced, an undesirable decomposition product because of its reactivity, instantaneously reacts with iron(III) oxide, which is included in the reaction container, to produce sodium oxide (Na2O) and Iron (Fe).

[Source: H. Stephen Stoker, Chemical Principles]