As the National Highway Traffic Safety Administration continues to investigate why millions of Takata-produced airbag inflators have a tendency to spew pieces of shrapnel with enough force to injure or kill occupants, the agency has opened a second probe into another airbag manufacturer for similar rupture issues.

The Wall Street Journal reports that federal regulators opened an investigation into ARC Automotive Inc.-produced airbag inflators used in Fiat Chrysler and Kia vehicles after receiving complaints that the devices can rupture, sending metal fragments flying at passengers.

In all, the investigation covers the airbag inflators found in nearly 420,000 model year 2002 Fiat Chrysler Town and Country minivans and about 70,000 model year 2004 Kia Optima sedans.

According to documents [PDF] posted by NHTSA, the agency opened the investigation after concluding that a consumer complaint received in December 2014 and an injury incident report submitted by Kia Motors last month, both regarding ARC inflators, were related. Both of the complaints involve injuries but no fatalities.

The first complaint concerns a 2009 incident in which the driver’s side airbag inflator ruptured in a 2002 Chrysler Town and Country minivan.

“My wife was turning into our driveway and collided with a snowmobile,” the complaint states. “The driver side airbag deployed. There was a problem with the inflator and the airbag exploded putting shrapnel into her body. Because of the location of the airbag and the body, most of the shrapnel went into her chest, with the airbag plate breaking apart, striking her in the chin breaking her jaw in three places. If it hadn’t been for a great ambulance crew she would have bled to death. She was in a trauma hospital for three and a half months. She has permanent muscle and nerve damage, the jaw is not aligned correctly so she has problems eating.”

After receiving the complaint, NHTSA’s Office of Defects Investigations (ODI) contacted Fiat Chrysler and conducted a search for similar incidents. Based on information provided by the manufacturer and through its research, investigators determined that the 2009 incident was a single isolated event.

However, six months later, in June 2015, Kia notified ODI of a lawsuit that involved a 2014 incident in New Mexico in which the driver’s side airbag inflator ruptured in a model year 2004 Kia Optima.

After looking into the Kia lawsuit, ODI revealed that both the 2009 and the 2014 incidents included inflators supplied by ARC Automotive.

ARC manufactures inflators that other companies use in airbag modules that are then sold to vehicle manufacturers. The inflator used in both the Town and Country and the Optima is a hybrid design which relies on two distinct sources of energy.

According to NHTSA, the ARC inflator fills the airbag cushion by releasing an inert gas stored in the inflator at high pressure. This specific gas mixture is augmented by an ammonium nitrate based propellant – the same chemical used in defective Takata airbags.

ARC tells ODI that the pressurized gas mixture and propellant are contained entirely within a hermetically sealed steel housing and is therefore isolated from external atmospheric conditions.

A preliminary analysis of the Fiat Chrysler rupture – which involved an airbag module produced by Key Safety Systems that had a dual stage ARC inflator – found that the exhaust path for the inflation gas mixture may have been blocked by an unknown object. The blockage appears to have caused high internal pressure and the subsequent rupture of the inflator assembly, NHTSA reports.

As for the Kia incident, the airbag module in question was manufactured by Delphi and had a single stage ARC inflator, investigators have yet to determine the root cause of the rupture.

“At the present time it is unknown if there is a common root cause in these incidents. ODI is opening this investigation in order to collect all known facts from the involved suppliers and vehicle manufacturers,” NHTSA reports.

The investigation into the ARC inflators comes just two months after Japanese auto parts maker Takata caved to regulator pressure and recalled 33.8 million vehicles equipped with defective airbags.

Regulators first opened a probe into Takata-produced airbags in the summer of 2014. Since then, eight deaths and more than 100 injuries have been linked to the explosive inflator ruptures.

Much of the investigation into the Takata airbags have surrounded the company’s use of ammonium nitrate as its main propellant. The chemical is known to become unstable over time, especially when exposed to moisture, a revelation that led regulators to first recall vehicles in high humidity areas of the U.S.

Regulators, car manufacturers and Takata continue to determine why the airbag inflators malfunction.

U.S. Regulators Investigating More Air Bags Following Two Incidents [The Wall Street Journal]

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