The emerging crisis over air bags traces back to a little-known Japanese company that for over 20 years has supplied the safety devices to automakers including Toyota Motor Corp., Honda Motor Co. and General Motors Co.

Air bags made by Takata Corp. are linked to at least four deaths and more than 30 injuries in the U.S. after the safety devices deployed with too much force, spraying metal shrapnel at occupants. U.S. authorities have begun an investigation and more than 7 million cars made by 10 automakers have been recalled to fix the hazard. 

Though the probes are ongoing, one focus is likely to be Takata’s choice of an unusual explosive chemical to inflate its air bags in milliseconds, according to auto industry executives. The Japanese parts maker four years older than Toyota also has said it dealt with lapses in quality control at its plant in Mexico.

“No other supplier other than Takata has used this ammonium nitrate,” said Jochen Siebert, Shanghai-based managing director of JSC Automotive Consulting, which advises automakers and parts suppliers. “You could build air bags that were smaller and lighter. It was all about technology; it wasn’t even about price. But it all went wrong.”

The unfolding crisis marks a fall from grace for a Tokyo-based company that rode Japan’s postwar industrialization to became a global powerhouse in seat belts that saved lives. Having now been responsible for making some vehicles more dangerous, Takata’s failures add to growing doubts about auto safety and how well motorists are protected by regulators.

Takata’s recent woes are rooted in air-bag inflators, a component it started making in 1991 in Moses Lake, Washington.

While parachutes deploy by the relatively simple act of pulling a ripcord, the inflators that set off air bags are more complex. Chemical compounds are used to form propellant, which is compressed into aspirin-like tablets.

In less time than it takes to blink, an igniter heats up the tablet inside a high-strength steel tube after a crash. The ensuing chemical reaction fills the air bag with gas, inflating it at more than 200 miles per hour.

In the late 1990s, Takata made ammonium nitrate the chemical-of-choice for its air-bag inflator design, said Siebert, who was advising for the air bag market in Europe at the time.

The compound went into the earliest model-year cars that have been recalled in the past two years, including Bayerische Motoren Werke AG’s 2000 BMW 3 Series, Honda Motor Co.’s 2001 Accord and Civic and Nissan Motor Co.’s 2001 Maxima and Pathfinder. (Bloomberg)