Paul Brand: Air bags deploy to reduce harm, not increase it

Q We are looking for information on air-bag deployment. Firsthand knowledge of a demonstration would be helpful.

Is there any noise? If so, to what degree? Loud?

Does the accompanying powder get in your eyes? If so, can it affect your vision temporarily?

If two bags go off; i.e., driver and passenger, what would be the effect?

Would a 5-foot-10 driver be hit in the face, the chest or both?

We are not attempting to malign air bags at all, but merely to establish the physical and mental affect, if any, on a driver after the air bags deployed in an accident. Would the driver be confused or startled?

A Does sitting in the driver's seat of a GM truck as the air bag is triggered count? Several years ago I did a TV piece to show viewers what happens when an air bag deploys. The folks at GM were gracious enough to trigger the driver's air bag while I sat in the front seat, and the TV cameras filmed it in slow motion.

The nontoxic talcum-type powder in the air-bag module, designed to lubricate the fabric air bag so that it deploys smoothly, did not get in my eyes during the demonstration. Could it during an actual crash? Yes, but so could all the dirt, dust and debris generated by the impact.

What happens if both front air bags deploy? Both front occupants would benefit from the added protection. With the latest generation of air bags, sensors in the passenger front seat deploy the air bag only if the seat is occupied. The front passenger air bag is significantly larger than the driver's air bag, deploys using the windshield as a backstop and covers a wider area to ensure that it protects the front-seat passenger.

Would a driver be hit in the face or chest? This is the key issue you raise. It's important to recognize that the air bag is designed to fully deploy before the occupant "arrives" in the zone of deployment. This is why seat belt use is critical and fundamental to air-bag deployment. Air bags are supplemental restraint devices, meaning they are engineered to function in conjunction with the seat belt.

Here's the scenario, and it all occurs in just more than one-tenth of a second. During a significant frontal crash, the vehicle begins to decelerate extremely rapidly at impact. If the air-bag sensors determine that deployment will benefit the occupant, the air bag is triggered. As this is happening, the occupant is still moving forward at the vehicle's original speed. The seat belt is beginning to decelerate the occupant and keep the occupant in position in the seat. As the air bag is deploying, the occupant is still decelerating toward the air bag as the seat belts stretch to some degree to slow the rate of deceleration of the occupant's body. The air bag reaches full deployment before the upper body of the restrained occupant reaches the "bubble" or zone of deployment. The air bag now provides a cushion or pillow effect to continue to slow the rate of deceleration and reduce the level of force imparted to the occupant's body. The air bag is deflating as this occurs, and just more than a tenth of a second -- about the blink of an eye -- after it is triggered, the air bag is spent and deflated.

In terms of the mental and physical effects of air-bag deployment, I don't believe you can evaluate air-bag deployment without recognizing the totality of the event that triggered the air bag -- a significant-to-catastrophic frontal crash. With air-bag deployment, the occupants may well be stunned and confused from the overall effects of the crash. In a catastrophic frontal crash, they may well suffer injuries.

In the same frontal crash without air bags, all of the "sudden stop" forces of deceleration to the occupant's body are imparted by the surface area of the seat/shoulder belt.

Remember the four causes of injuries in a motor vehicle crash: bodily impact with some portion of the vehicle or environment; some part of the vehicle collapsing and affecting the body; some outside object penetrating the vehicle and striking the body, and fire.