Hours after reports began swirling that federal regulators were poised to more than double the already massive Takata airbag inflator recall at some point this week, the National Highway Traffic Safety Administration announced it had amended a previous order and directed the Japanese parts maker to add 35 to 40 million additional airbags to the recall list that already includes 28 million shrapnel-shooting airbags. 

NHTSA officially expanded the recall on Wednesday after the agency and independent experts reviewed [PDF] the findings of three independent investigations into the Takata air bag ruptures and confirmed the findings on the root cause of inflator ruptures.

According to the amended consent order [PDF] issued to Takata, the company is required to make a series of safety defect decisions that will support vehicle manufacturer recall campaigns of an additional estimated 35-40 million inflators.

The expansions are planned to take place in phases between May 2016 and December 2019.

With the expansions, NHTSA notes that all Takata ammonium nitrate-based propellant driver and passenger frontal air bag inflators without a chemical drying agent, also known as a desiccant, will be recalled.

“Today’s action is a significant step in the U.S. Department of Transportation’s aggressive oversight of Takata on behalf of drivers and passengers across America,” Transportation Secretary Anthony Foxx said. “The acceleration of this recall is based on scientific evidence and will protect all Americans from air bag inflators that may become unsafe.”

NHTSA confirmed investigators’ previous determination that the root cause of the violent ruptures was a combination of three factors: time, environmental moisture, and fluctuating high temperatures contribute to the degradation of the ammonium nitrate propellant in the inflators.

“The science clearly shows that these inflators become unsafe over time, faster when exposed to humidity and variations of temperature,” NHTSA administrator Mark Rosekind said Wednesday. “This recall schedule ensures the inflators will be recalled and replaced before they become dangerous, giving vehicle owners sufficient time to have them replaced before they pose a danger to vehicle occupants.”

NHTSA says the five recall phases are based on prioritization of risk, determined by the age of the inflators and exposure to high humidity and fluctuating high temperatures that accelerate the degradation of the chemical propellant.

The agency plans to work with affected vehicle manufacturers to determine which vehicles are affected and to revise the coordinated remedy plan for obtaining and installing replacement inflators.

It’s unclear how many vehicles will be affected by the expanded recall, as some cars have more than one inflator, and not all inflators are made by the same manufacturer.

“Everyone plays a role in making sure that this recall is completed quickly and safely, including manufacturers, suppliers and vehicle owners themselves,” Rosekind said. “People who receive notification that there is a remedy available for their vehicle should act immediately to have their inflator fixed.”

Wednesday’s expansion does not include airbag inflators that include a chemical desiccant that absorbs moisture. NHTSA previously gave Takata until the end of 2019 to prove that inflators with a drying agent are safe.

As part of its amended consent order, NHTSA directed Takata to step up its testing of inflators with drying agents now that the root cause of the inflator ruptures is known.

The parts maker is required to provide a testing plan for the inflators within 60 days.

While the recall is a step toward getting all Takata-airbag equipped vehicles off the roads as some lawmakers and safety groups have pushed for, the pace of repairs continues to worry some.

“The largest auto recall in our nation’s history just doubled but, unfortunately, the pace at which Takata and the automakers are replacing these faulty airbags has not,” Florida Sen. Bill Nelson said Wednesday. “The top priority must be doing whatever is necessary to get these potentially-deadly airbags out of people’s cars as quickly as possible. If we wait another three or four years for these to get replaced more people are likely to die”

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