NHTSA is finally putting an end to ammonium nitrate as an airbag propellant. One of the key takeaways from the Takata airbag debacle is that the manufacturer uses unsafe, volatile propellant. When ammonium nitrate is exposed to moisture, the chemical’s explosive properties are changed, typically for the worse.
It appears the National Highway Traffic Safety Administration has reached the limit of its patience in the Takata airbag disaster. Not only is NHTSA overseeing the recall efforts of 19M U.S. vehicles and replacement of 23M possibly defective airbag inflators, NHTSA put the hammer down on airbag propellant.
That last may be a poor choice of words given the reason for NHTSA’s order that ammonium nitrate is no longer to be used as an airbag propellant. Ammonium nitrate, (NH4)(NO3), may be more familiar some for its use in fertilizers. As we know from the mining industry (and other, less savory, efforts), when you combine ammonium nitrate with fuel oil, it makes a powerful explosive. As a matter of fact, it’s the most common explosive used in mines, surpassing the one everyone always thinks is the most common: dynamite.
NHTSA issued consent order to Takata Corp. The order hit the company with a civil fine of about $70M but also included the phase-out of ammonium nitrate. As a NHTSA representative put it, good old (NH4)(NO3) is “a factor in explosive ruptures that have caused seven deaths and nearly 100 injuries in the United States.” The consent order also sets the schedule for future recalls of “all Takata ammonium nitrate inflators now on the roads unless the company can prove they are safe.”
Takata has taken the position that it cannot find a cause for the airbag inflator defects. NHTSA basically said, “Talk to the hand,” finding that “Takata provided NHTSA with selective, incomplete or inaccurate data” since 2009 and gave the same misleading data to its customers.
If you’re like me, you’re wondering how the ammonium nitrate became so volatile. Surely, there was no fuel oil involved, right? Correct. However, there was potentially some moisture of the water variety. Chemistry experts warn that exposing ammonium nitrate to moisture can degrade the chemical in ways that change its explosive power.
Takata is currently the only airbag manufacturer in the world to use ammonium nitrate as an airbag propellant. Other manufacturers use far more stable propellants.
The airbag disaster is quite serious. When the faulty airbags do explode, they do so with such force that the shrapnel from the airbag casing is essentially weaponized; picture a Claymore directional anti-personnel mine. Granted, the explosive power isn’t the same and the shrapnel is different, but the effect is quite similar.
Moving away from the use of unsafe, unstable propellants will hopefully prevent more injuries. Of course, we need to get the existing (NH4)(NO3) off the streets first.