Scientists find cause of Takata air bag explosions
Inflator assembly doesn't adequately prevent moisture from intruding in very humid conditions.
DETROIT — Scientists hired by the auto industry have determined that multiple factors – including moisture and high humidity – can cause some Takata air bags to inflate with too much force and hurl shrapnel at drivers and passengers.
The Independent Testing Coalition, which has been investigating the cause for the past year, announced its findings.
Air bags made by Japan’s Takata Corp. have caused at least 10 deaths and 139 injuries worldwide. The exact cause of the problem has eluded investigators for more than a decade, although more recent probes have focused on Takata’s use of ammonium nitrate to create a small explosion and inflate the air bags in a crash.
The Virginia rocket science company Orbital ATK, which was hired by the coalition, determined that three factors, working together, can cause the air bags to explode. Using specially-formulated ammonium nitrate without a moisture-absorbing substance – as Takata does – increases the risk of an explosion after long-term exposure to high temperatures and moisture. Orbital ATK also found that Takata’s inflator assembly doesn’t adequately prevent moisture from intruding in very humid conditions.
The coalition said its findings apply to around 23 million of the 28 million Takata air bag inflators that have been recalled by the U.S. government. All of those air bags use specially-formulated ammonium nitrate without a drying agent. The findings may apply to all of the air bags, but scientists focused on the 23 million that were recalled before this year. Five million additional inflators were recalled in January.
David Kelly, a former acting administrator of the National Highway Traffic Safety Administration and the coalition’s project manager, said that while humidity and ammonium nitrate have been discussed as factors, this is the first time scientists have determined that all the factors combined are causing the explosions. Kelly also said the design of the inflator is coming under more scrutiny than it has in the past.
Kelly said determining exactly what was causing the explosions was a critical step. Now, investigators will focus on the performance of the inflators that are being used as replacement parts in ongoing recalls of Takata air bags. He said owners whose vehicles have been recalled should continue to get their air bags replaced while the investigation continues.
“If you don’t have the root cause, you’re just throwing stuff up on the wall,” he said. “You may never get to a situation where you can have an end game.”
Takata has given multiple explanations for the problem, including quality control problems at manufacturing facilities and exposure of the air bags to high humidity.
Frustrated by the numerous explanations and the slow pace of the investigation, 10 of Takata’s customers – Toyota, BMW, Fiat Chrysler, Ford, General Motors, Honda, Mazda, Mitsubishi, Nissan and Subaru – formed the Independent Testing Coalition and hired Orbital ATK in February of last year. Orbital makes rocket propulsion systems, small arms ammunition, warhead fuses and missile controls.
Kelly said he’s not sure how long the next phase of the investigation will take. Scientists need to replicate the behaviour of air bags over a period of several years, which will take time, he said.
In a statement, Takata said the coalition’s results are consistent with its own testing. Takata said age and long-term exposure to heat and high humidity appear to be significant factors in cases where inflators have malfunctioned. The company said it is co-operating with the coalition and the US government.
But lawmakers’ patience is wearing thin. Democrats on the Senate Commerce Committee issued a report Tuesday alleging that Takata has been manipulating test data on its air bags for well over a decade. The report said emails and other records show that as late as 2013 – several years after recalls of the air bags began – a director at Takata was ignored when he complained to superiors that they were wrongly limiting the population of air bags that needed to be recalled.
“This is not only inexcusable, it’s reprehensible,” Sen. Bill Nelson, D-Florida, said Tuesday in a speech on the Senate floor.
Nelson said NHTSA needs to accelerate the recalls of Takata’s air bags.
Takata’s faulty inflators are used in both driver and passenger-side air bags. Globally, about 50 million inflators are subject to recall. US safety investigators have said that the number of recalls is certain to grow as more tests are done.
Analysts say there could be 50 million or more Takata inflators in US cars and trucks that haven’t been recalled yet. Takata must prove to U.S. regulators that the inflators are safe or all of them will be recalled starting in 2018.