The sound of an airbag deploying is loud, like the cracking of a whip. Really, it’s the noise of an explosion.
When car sensors detect a crash, a chemical reaction is triggered by the ignition of a solid hunk of propellant. The way propellant works in an airbag comes down to heat, moisture, and timing. A wad of chemicals sits inside a flattened metal canister until heated up—which makes those chemicals expand quickly and gaseously when the airbag needs to inflate. Vents on the back of the bag prevent the whole thing from being blown to bits. All this happens in about half the time it takes for a person to blink: between 100 and 200 milliseconds.
That’s how it’s supposed to work, anyway.
But as many as one in seven cars on the roads in the United States may have defective airbags. That’s the scope of the ongoing automotive recall that includes 34 million cars—Toyota, Nissan, Honda, Mazda, Mitsubishi, General Motors, Subaru, Ford, Chrysler, and BMW are all affected. The defective Takata-made airbags explode with shrapnel, spraying motorists with sharp bits of metal, and have caused more than 100 injuries and at least eight deaths in the past decade.
The faulty airbags are being traced back to the chemical compound Takata now uses for propellant. The manufacturer changed the main ingredient from tetrazole to ammonium nitrate in 2001. Takata has defended its continued use of the latter, calling it “safe and effective for use in airbag inflators when properly engineered and manufactured,” in a statement. But employee emails show that there were “dire warnings about safety and quality lapses years before Takata Corp. would fully acknowledge the threat posed by its defective airbags,” according to a report by the Senate Commerce Committee this week. Senator Bill Nelson, a Floridan Democrat, says it now appears that Takata was aware of “serious safety and quality control lapses” in its factories as early as 2001.