If you're driving a used car or had your own repaired lately, you may be missing something: an airbag that works.

An airbag found in a garage in Burlington, Ontario, stuffed plastic shopping bags.

Police are calling fake airbags a growing scam.

Two years ago, 53 year Najma Ladhani was alone in her car just outside Vancouver. She was wearing her seatbelt.

For a reason we'll never know, Ladhani swerved into an oncoming vehicle.

When police arrived she was crushed over the steering wheel. Her airbag, which should have protected her, didn't.

"The family is devastated. To us it's a senseless death," the victim's niece, Shaheen Tejani, told Marketplace.

Fake airbags 'a huge problem'

Accidents happen all the time, but what makes Najma's death so different is what police discovered later. The airbag in her car was fake. Police say she'd be alive today if it had been real and working.

There's no way to say how big a problem "fake airbags" is in Canada, but US police believe its huge. They say thousands of people are driving on North American highways with absolutely no idea their airbags, like Najma's, are fake.

Tejani still shudders remembering the police officer describing the fake airbag.

"He showed me the steering wheel with a piece of foam under the part that says there's an airbag there. It was just some glue and a piece of foam, and it just shocked everyone."

There's no way to tell how many fake airbags are in Canada. But U.S. police say it's a huge problem.

Miami police were shocked when they launched Operation Hot Air two years ago, and found out there are thousands of fake airbags.

Captain Tom Hunker heads the Murder & Fraud Division of the North Miami Beach police.

"We have one place here just outside the city that admitted to selling over six thousand just shells….so we know that this is a very profitable thing for these people to get involved in."

Police say "fakes" — or dummy bags — are big business because new airbags cost so much, sometimes thousands of dollars.

'Socks, beer cans, paper and styrofoam' stuffed in airbag compartments

As police pursued Operation Hot Air, they found even more fakes. Miami Detective Richard Rand says some airbag compartments were stuffed with styrofoam.

"It comes out of a can, costs a couple of dollars and you can buy it in any store… It dries to give you a hard feeling so if you pressed on this you think that there is something there, and it's styrofoam."

"I've heard of airbags being stuffed with socks, beer cans, paper and also styrofoam seems to be a popular material," Rand continued.

This airbag compartment was filled with styrofoam

A recent survey in Los Angeles found of 1,200 vehicles that had replaced airbags, 66 were fake.

"If you spread that nationally, even between the U.S. and Canada, that's one in 25 cars that have a fake bag. You can imagine the potential for these cars getting into an accident and somebody getting seriously injured or killed," Captain Hunker said.

Marketplace called a handful of mechanics who inspect used vehicles.

In Vancouver, Gordon Hemrich has found 10 fakes in 12 months. He says there are some clear signs that a car may have a fake airbag: "Well, it's soft in here and usually when there's an airbag it's hard… What they do, they take out the remaining airbag inside, then they get it repaired by an upholstery guy, and just seal it off and paint it to make it look good."