Fewer than half of the 41 million potentially explosive airbag inflators made by Japanese company Takata have been replaced in the several years since the largest auto-safety recall in U.S. history.

Some Honda employees are going door-to-door knocking, hunting for roughly 100,000 cars with the most dangerous defective Takata airbags that have up to a 50/50 chance of failing. Faulty Takata airbags have killed at least 13 people in the U.S.

Millions of mailers, phone calls and even targeted Facebook ads haven’t gotten to everyone, so Honda has 500 people working in so-called “pit teams,” canvassing neighborhoods nationwide. They’re looking for unrepaired 2001-2003 Hondas and Acuras.

Teams carry replacement airbags allowing a technician to remove the defective one on the spot.

Honda’s Ed Cohen said going door to door to inform customers is “unprecedented.”

“It has never been done before,” Cohen said. “The challenge here is that these vehicles are 14, 15, 16 years old. They change hands one to three times.”

In Orlando, Jose Ramon Rivera watched as a pit team changed the airbags in his 2001 Honda that he bought two years ago.

But there’s a second challenge for the automaker: As many as 144,000 vehicles with the dangerous air bags may have ended up in scrap yards, and some have been be repaired and resold.

Karina Dorado, 18, didn’t know her car was was salvaged from a junkyard. She was nearly killed when its Takata airbag deployed in March.

Tim McMillon actively seeks out older wrecked Hondas. He removes the airbags before putting them in his Orange City, Florida, salvage yard.

He’s pulled about 100 defective airbags so far this year. “It’s out of the car, it’s out of the system, Honda knows about it — it’s gone,” McMillon said. 

Honda says it’s been able to get about 80,000 of these dangerous air bags from salvage yards, and another 50,000 or so have been found from the canvassing effort this year. But many more remain to be found.

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