The safety of car air bags is once again being questioned after a Toronto woman was killed in a seemingly minor traffic accident.

Karol Steinhouse, 47, died last Wednesday after a chain-reaction accident involving her 2000 Acura and three other cars. The accident caused less than $1,000 total damage but deployed Steinhouse's driver-side air bag.

The mother of two had no vital signs when emergency crews got to her, and was pronounced dead at hospital 30 minutes later. It's not clear whether she was wearing her seat belt.

Transport Canada's recommendation on air bags

An autopsy showed the woman was killed by blunt force trauma that broke six of her ribs and ruptured her aorta.

Toronto police are investigating the case along with Transport Canada and Honda. They hope that data from the car's so-called "black box" will tell them what caused the air bag to deploy and whether or not Steinhouse was wearing her seat belt.

An air bag can deploy at almost 300 kilometres an hour. That's why Transport Canada advises drivers and passengers to be positioned as far from the dashboard as possible, and to always wear seat belts.

When seat belts are worn, air bags have a 75-per-cent efficacy rate of preventing head injuries and 66 per cent for chest. The bags are thought to have saved about 300 lives since being introduced to Canada.

But they are also thought to be responsible for at least six deaths. In all the accidents involving death, the victims were either not wearing seat belts or wearing them improperly, says the Canada Safety Council.

Steinhouse's petite stature may have been a factor. She was four feet 10 inches, and may have pulled her seat very close to the steering wheel.

Transport Canada recommends car drivers and passengers keep 25 centimetres between the centre of the air bag cover and the centre of their sternums. If, drivers cannot maintain a distance of 25 cm, they should consult their vehicle manufacturer for help.