Azide, Sodium
Sodium azide is a highly toxic white crystalline solid. It has come into widespread use in automobile air bags; its explosive decomposition to nitrogen gas provides rapid inflation of the air bag. In addition, sodium azide is used in the production of metallic azide explosives and as a preservative in laboratories. It has no current medical uses, but because of its potent vasodilator effects, it has been evaluated as an antihypertensive agent.
Mechanism of toxicity
The mechanism of azide toxicity is unclear. Like cyanide and hydrogen sulfide, azide inhibits iron-containing respiratory enzymes such as cytochrome oxidase, resulting in cellular asphyxiation. In the CNS, enhanced excitatory transmission occurs. Azide is also a potent direct-acting vasodilator.
Although neutral solutions are stable, acidification rapidly converts the azide salt to hydrazoic acid, particularly in the presence of solid metals (eg, drain pipes). Hydrazoic acid vapors are pungent and (at high concentrations) explosive. The acute toxicity of hydrazoic acid has been compared with that of hydrogen cyanide and hydrogen sulfide.
Toxic dose. Although several grams of azide are found in an automobile airbag, it is completely consumed and converted to nitrogen during the explosive inflation process, and toxicity has not been reported from exposure to spent air bags.
Inhalation. Irritation symptoms or a pungent odor does not give adequate warning of toxicity. The recommended workplace ceiling limit (ACGIH TLV-C) is 0.29 mg/m3
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