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As a former director of engineering of a defense-products company, I’m very aware of the explosive nature of sodium azide. I know that there have been serious explosions in industries (including the airbag industry) that use metal azides. A few reasons sodium azide may have been selected for use in airbags are it releases gas fast, the gas it releases is pure nitrogen (of course, when sodium azide is mixed with other explosive or pyrotechnic ingredients, the resulting gas composition is altered), and it’s fairly stable when it’s inside an airbag system under most environmental conditions automobiles encounter. Some reasons that airbag companies should be seriously looking for alternatives to sodium azide include the lethal threat to anyone exposed to sodium azide in the presence of moisture, which your story addressed quite well; the compound’s explosive nature; and compatibility issues concerning the use of azides. In the event that a chemical pathway somehow leads to the formation of more-sensitive metal azides, the resulting chemicals are more prone to accidental detonation. It’s a tribute to airbag designers, airbag companies, and automobile manufacturers that they haven’t had more problems with sodium azide.

James F. Kowalick
Oregon House, Calif.

In reading this article, I didn’t see any reference to what, if anything, is being done to regulate the disposal of airbags in light of the health hazard involved. Also, it’s not clear to me what the effect will be on the general environment as we accumulate millions of airbags in junkyards around the world. I found myself terrified by this article.

Al Rosen
Aptos, Calif.