Thousands of Canadians are driving cars with very dangerous airbags: in an accident, they could explode with far too much force or fail to deploy at all.

Test on rebuilt airbags shows the bag did not deploy correctly - and deployed with explosive force.

They are rebuilt airbags; made with parts from other bags.

Last November, the Quebec government's public car insurance company issued a warning about the bags, which prompted a nationwide recall.

Marketplace and Radio Canada's consumer show La Facture have tracked the dangerous rebuilt bags from Quebec to body shops across Canada. We tested the airbags with dramatic results.

A rebuilt airbag explodes with frightening force, spewing burning gases.

The rebuilt airbags are prepared for testing and we watch with engineer Michel Gou of Montreal's Ecole Polytechnique. He's an expert in accident reconstruction.

This is how an airbag is supposed to deploy.

"First of all you see that there was no real deployment. Usually, there is a seam here and both covers are supposed to separate and the airbag is supposed to come out," Gou said after the test.

There was no separation. The airbag came out the side of the steering wheel. Also, a metal disc — about the size of a fist — separated from the cartridge and could easily have become a projectile.

Our second test was not as spectacular — but just as dangerous. The airbag did not fill up completely, offering little protection for the driver.

Donna Walton of Vineland, Ontario drove with rebuilt airbags for more than a year. The Waltons bought them after their original bags saved Donna from serious injury in an accident.

"I was on my way to take my son to a doctor's appointment when a deer jumped right out ahead of me and I didn't even see it coming. I hit it and the airbags went off and the whole front of the van was crushed in. Luckily nobody was hurt. I'm sure the airbags protected us."

Doug and Donna Walton replaced their airbags with rebuilt ones. They weren't concerned that the bags were rebuilt because their insurance company recommended them.

Donna and Doug Walton of Vineland, Ontario, drove with rebuilt airbags for more than a year

Although there are no reports of death or injury from rebuilt airbags, last November, Quebec declared them dangerous and recalled them.

The Waltons heard from their body shop two months after the recall notice was issued.

"I thought everything was OK until we got that recall notice and then I was very frightened to drive the van because I was scared they'd go off," Donna Walton said.

The rebuilt bags taken from the Waltons' van were held together by tape. One was cracked in several places.

Rebuilt airbags: bits and pieces of other bags - and gunpowder

Rebuilt airbags are made from bits and pieces of other used bags. At least 11,000 similar airbags were made in Quebec and sold at auto body shops and garages across Canada. They sold for about $500. Installing new airbags can cost up to $3,000.

And that's just what this was all about:

• money
• drivers looking for a deal
• auto body shops wanting to do business
• insurance companies reluctant to pay the full cost of new airbags.

It was a real opportunity for a young entrepreneur.

That's where Stephan Demers come in. The 29 year old Quebec City businessman had two small factories at which they rebuilt airbags. The Waltons' rebuilt airbags were made in his plant. So were 11,000 other unsafe airbags sold to people from Newfoundland to B.C.

Engineer Michel Gou has tested Demers airbags.

"He would put some chemical — sodium iodide — in there and he would fit that initial charge with gunpowder."

How did he know how much gunpowder to put in?

"Well, this is the problem," Gou said. "I don't know if he knew. I don't know if he would control that amount of gunpowder. But obviously since we had some catastrophic failure, he was putting too much."