Volvo Side-Impact Airbag System

Understand operation of Volvo Side Impact Airbags

The federal government estimates that 31 percent of all vehicle accidents resulting in injury or death are side impacts. Six vehicle manufacturers, working to meet federal government standards, have incorporated side-impact airbags in their 1997 model year vehicles.

Engineered to help act as a barrier between the seat occupant and the door, SIPS airbags deploy in certain side impacts. The bags can reduce forces on the occupants inside by over 40 percent and primarily help reduce chest, pelvic and head injuries.

With the introduction of the 1997 model year, side-impact airbags are available from the following manufacturers:

• Volvo - All 1997 models
• Mercedes-Benz - E-Class, S-Class and SL-Class autos
• BMW - 5-Series & 7-Series
• Cadillac - DeVille and Catera
• Lexus - LS 400
• Audi - A 8

There is no standard location or operating mechanism for these new side airbags and rescue personnel should be concerned. This training notebook describes only the Volvo side-impact airbag system. Additional notebooks will address details of the other systems.

All 1997 Volvo automobiles provide a driver and passenger front airbag along with two side-impact airbags, one on the outside edge of each front seat. Each bag is concealed inside the seat's side bolster, the thicker padded area along the door-side edge of the seat. The side-impact bag inflates when dedicated sensors indicate a side impact. Due to the very limited distance between the side of the vehicle and the occupant, these side airbags inflate in about 12 milliseconds or about three times faster than required by a frontal airbag.

A Volvo side-impact airbag works in the following manner:

1. With enough force (equivalent to a side impact at a minimum of about 11 mph) the side of the Volvo deforms inward. The inner door panel contacts the front seat frame along the rocker panel.

2. The crushed door pushes against a mechanical pyrotechnic sensor located at the front outside edge of the seat.

3. When sufficient force impacts the trigger device of the sensor, it creates an ignition flash. The tiny explosion generates a "pressure wave" that acts like a lit fuse. The wave burns through the flash tubing igniter line inside the seat at a speed of 6,000 feet per second.

4. The pressure wave activates two airbag gas generators, each charged with two grams of nitro-cellulose explosive gunpowder. The generators go off one after the other, within three milliseconds. This instantaneous sequencing inflates the bag more gently and keeps it inflated longer.

5. The expanding gases, mostly nitrogen, pushes the airbag through a seam in the upholstery as it inflates. The bag fully deploys seven milliseconds after triggering, around 12 milliseconds from the impact. The deployed bag has a volume of 12 liters and is one foot by eight inches in size.

6. The side-impact airbag cushions the occupant of the front seat as gases escape through two holes. The holes direct hot exhaust gases down and away from the occupant.

Task: Identify components and function of Volvo Side Impact Protection System airbag on a 1997 model year Volvo vehicle.

Ron Moore, a Firehouse contributing editor, is a battalion chief and the training officer for the McKinney, TX, Fire Department. He also authors a monthly online article in the Firehouse.com “MembersZone” and serves as the Forum Moderator for the extrication section of the Firehouse.com website. Moore can be contacted directly at [email protected].