MELISSA BLOCK, HOST:
We've heard the staggering number - 34 million cars with defective air bags, the largest auto recall in U.S. history. The company at the center of this is the Takata Corp. Today lawmakers grilled auto industry executives and federal safety regulators for answers. As Jason Margolis reports, members of Congress are trying to determine what caused the problem and if the replacement air bag parts are safe.
JASON MARGOLIS, BYLINE: Are we safe, or merely safer? That was the question repeatedly posed by Congressman Michael Burgess, Republican from Texas.
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MICHAEL BURGESS: We don't have any great clarity as to the root cause and how we will know when we get to that point where we are safe. Clarity and transparency are indeed needed.
MARGOLIS: Burgess was speaking to auto executives and National Highway Traffic Safety Administrator Mark Rosekind. He updated committee members on the root cause of defective air bags.
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MARK ROSEKIND: Some factors appear to have a role, such as time and absolute humidity. The full story is not yet known and a definitive root cause has not been identified. In my recent experience as an NTSB board member and a veteran of many major transportation investigations, it may be that there is no single root cause, or the root cause may never be known.
MARGOLIS: Rosekind said part of the difficulty in testing is that there are more than 10 different configurations of the inflator.
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ROSEKIND: That's part of the problem. In fact, there are some Takata air bags in certain manufacturers that have ruptured in some manufacturers', but not other manufacturers' cars.
MARGOLIS: Engineers are confident the problem is caused by exposure to high heat and humidity. This can cause the chemical ammonium nitrate to degrade over time. Marsha Blackburn, a Republican from Tennessee, raised concerns about what chemicals Takata is using in replacement air bags.
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MARSHA BLACKBURN: Are you satisfied with the information that Takata has provided to you on their propellant mix?
ROSEKIND: We're working our way through that information. They have been open about providing us testing data...
BLACKBURN: OK.
ROSEKIND: ...But the information that you're asking about was millions and millions of pages.
MARGOLIS: Takata's executive vice president of North America, Kevin Kennedy, spoke next. He struck a penitent tone, expressing deep regret for his company's defective air bags. He tried to assure committee members that replacement parts were indeed safe, but many weren't convinced, including Democrat Jan Schakowsky of Illinois. She didn't understand why ammonium nitrate was still being used by Takata.
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JAN SCHAKOWSKY: So the replacement could be as dangerous as the current? Why would you even replace it?
KEVIN KENNEDY: Well, we - as I said, without really exactly understanding the root cause and continuing to test outside of the bounds of what we've already recalled, we're trying to determine that.
MARGOLIS: The other issue is availability. There simply aren't enough kits to replace the potentially faulty air bags. Kennedy said Takata has doubled the production of replacement kits to 700,000 a month and the company is turning towards its competitors.
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KENNEDY: Half of the replacement kits we shipped last month contained inflators made by other suppliers. And by the end of the year, we expect that to reach 70 percent.
MARGOLIS: Still, it's expected to be two years before there are replacement parts for all 34 million vehicles that need them. Jason Margolis, NPR News. Transcript provided by NPR, Copyright NPR.