HowStuffWorks "How Airbags Work"
Note on page 2--
It didn't take long to learn that the force of an airbag can hurt those who are too close to it. Researchers have determined that the risk zone for driver airbags is the first 2 to 3 inches (5 to 8 cm) of inflation. So, placing yourself 10 inches (25 cm) from your driver airbag gives you a clear margin of safety. Measure this distance from the center of the steering wheel to your breastbone. If you currently sit less than 10 inches away, you can adjust your position.
