(Bloomberg) -- Air-bag maker Takata Corp. gave in toU.S. regulators on Tuesday, agreeing to what will be the largestautomotive recall in history as investigators continue to searchfor the root cause of a defect that has killed at least sixpeople.

About 34 million cars are now on a list for an air bagreplacement, almost double the number that had already beenrecalled. With vehicles from 11 different automakers and a shortageof repair parts, it could take years for all the cars to be madesafe, said Mark Rosekind, the head of the National Highway TrafficSafety Administration.

“As far as we know, this is the largest recall in auto history,”Rosekind said at a news conference in Washington. “Others are doingresearch and suggest that it could be one of the largest if not thelargest of all of consumer recalls.”

As part of a consent order, Tokyo-based Takata agreedto make the recall nationwide -- a step it had resisted -- andsubmit its air-bag parts to the U.S. government for testing. Theagreement offers a way for Takata to resolve a globalauto- safety crisis that made it a target for lawsuits and hurt thecompany’s standing with the automakers it supplies.

“We are pleased to have reached this agreement with NHTSA, whichpresents a clear path forward to advancing safety and restoring thetrust of automakers and the driving public,” Takata ChiefExecutive Officer Shigehisa Takada said in a statement.

No Guarantees

Asked whether Takata has agreed to penalties, Rosekindsaid more than $1 million in fines have accumulated so far, andmore could come depending on the continuing investigation.

“They are suspended right now until we see what the goingforward plan is,” Rosekind said.

The case involves air-bag inflators that may have been degradedby moisture, causing them to deploy with too much force in a crash,breaking apart and sending shards of metal and plastic into thepassenger compartment of vehicles.

As part of the consent order, Takata released fourdefect reports, spelling out safety hazards on various sets ofvehicles. The company gives different estimates on how longreplacement inflators may last in different kinds of climates,including the high-humidity states that were the focus of the earlyrecalls.

Complex Coordination

NHTSA couldn’t provide a precise timetable on when repairs wouldbe complete because of the complexity of coordinating with so manyautomakers. Because the root cause of the defect still isn’t known,it’s uncertain that replacement air bags will last the entire lifeof the vehicles and it’s possible consumers will need a secondrepair in several years, Rosekind said.

“We know that the ones that are going in are safer,” Rosekindsaid. “The concern is, are they safe over the long term? That hasyet to be determined.”

Older vehicles and those in high humidity states would get thehighest priority in rolling out repairs, Takata said inits statement.

Senator Richard Blumenthal, a a member of a Senate panel thatgoverns transportation policy, has been pushing for a criminalinvestigation into Takata’s handling of the recalls.

Criminal Investigation

“Takata should have been much more aggressive before now inprotecting passengers through a national recall,” said Blumenthal,a Connecticut Democrat. “In the meantime the Department of Justiceshould be taking appropriate action to investigate and imposepenalties.”

Takata fell 1.1 percent to 1,507 yen in Tokyo tradingbefore the announcement was made in the U.S. The stock has lost 27percent in the past year, compared with a 42 percent gain byJapan’s benchmark Topix index.

NHTSA has been pressuring Honda Motor Co., Nissan Motor Co. andat least eight other automakers affected by the recalls to speedthe repair process and work with other air-bag suppliers to obtainparts. The agency also has demanded that Takata turn overmore documents and data from the devices that have been removedfrom the recalled cars.

Daily Fines

NHTSA in February began fining Takata $14,000 a dayfor not completely answering questions about air-bag inflaterproduction and company efforts to investigate the explosions. Itsaid at the time that most of the 2.4 million pages of documentsthe company had produced didn’t actually relate to the agency’sspecific inquiries.

The consent order puts NHTSA’s relationshipwith Takata on a new footing. While the potential formore fines is there as the formal investigation continues, thecompany and the regulator are now cooperating on testing,evaluating potential fixes, and coordinating repairs withautomakers.

The agency become more aggressive since it was lambasted byCongress for failing to be more active prior to last year’srevelation that about 2.6 million General Motors Co. cars had aknown ignition-switch defect that went unrecalled for years.

“NHTSA has done a 180-degree turn on how they’re handling thesesafety investigations,” Kevin Dean, who represents plaintiffs inseveral air bag lawsuits, said praising the agency. The recallsstill may not go far enough, he said.

Ammonium Nitrate

Modern air bags, credited by NHTSA with saving more than 2,000lives per year in the U.S., rely on chemical reactions to safelyinflate in milliseconds when sensors detect a crash. Takata’strouble has been linked by safety advocates and victims’ lawyers tothe company’s choice of chemical propellant, a type of ammoniumnitrate that can be rendered unstable by high humidity andmoisture.

In a properly operating device, gas created by an electricalcharge is released through holes in a metal canister to inflate theair bag. If the chemical propellant tablets are made improperly orhave degraded because of moisture, they vaporize with too muchpressure, potentially resulting in a burst canister that hurlsmetal and plastic shards.

“All of us have to do fact-checking to make sure they’re gettingevery vehicle with ammonium nitrate-based inflators, becausethey’re subject to deterioration over time,” Dean said.

One of the main disputes between Takata and NHTSA hadbeen over whether to initiate a national recall for some drivers’side air bags. The company had said the defect was tied to highhumidity, and it supported recalls limited to southern U.S. stateswith tropical weather. Today’s agreement makes all of the air-bagrecalls national.

In addition to Honda and Nissan, Takata’s other affectedcustomers in the U.S. market are units of Fiat Chrysler AutomobilesNV, Toyota Motor Corp., Bayerische Motoren Werke AG, Mazda MotorCorp., Ford Motor Co., General Motors Co., Fuji Heavy IndustriesLtd.’s Subaru and Mitsubishi Motors Corp.

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