Corrosion by the ammonium nitrate in the gas cylinders used in Airbags since 1999 has resulted in shrapnel being propelled through a vehicle when the canister deploys the airbag. This has resulted in at least 23 deaths
More than 14 million vehicles with the Takata-made airbags have been recalled worldwide over concern that they can explode violently when they deploy in an accident.
The New York Times discuses the switch by Takata from a safer compound (tetrazole) it was seen as a reliable and effective compound for inflating airbags. Ammonium nitrate on the other hand is highly sensitive to temperature changes and moisture, and it breaks down over time. And when it breaks down, it can combust violently
“It shouldn’t be used in airbags,” said Paul Worsey, an expert in explosives engineering at the Missouri University of Science and Technology. The compound, he said, is more suitable for large demolitions in mining and construction. “But it’s cheap, unbelievably cheap,” he added.
The tragedy is that this was discovered in 2004 by Takata where they secretly began testing out of hours and weekends.
Ammonium nitrate cycles through five solid states. As the vehicle goes from receiving the heat of sunshine to the cold overnight, the temperature swing is large enough for the ammonium nitrate to change from one phase to another, experts say. Ammonium nitrate also absorbs moisture from the atmosphere readily. Those two things together make ammonium nitrate tablets prone to damage, experts say.