Description & Operation: Notes

WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2000 BMW Z3, 2000 BMW 328i, 2000 BMW 323i, 1999 BMW Z3, and 1999 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.

WARNING: To avoid injury from accidental air bag deployment, read and carefully follow all WARNINGS and AIR BAG SAFETY PRECAUTIONS .

Supplemental Restraint System (SRS), also known as air bag system, is designed to provide increased accident protection for driver and passenger by deploying air bags in a front-end collision. The air bag system is designed to be used in conjunction with 3-point safety belts. The air bag system consists of driver-side air bag module (located in center of steering wheel), passenger side air bag module (located inside dash, above glove box), side impact air bags (located behind right and left front door trim panels), head impact air bag (located behind left and right side of headliner), electronic SRS control unit, contact ring, energy capacitor/voltage transformer (integrated into SRS control unit), AIR BAG warning light, driver-side knee bolster mounted under steering column, seat belt contacts and seat occupancy module.

When SRS control unit senses an impact, it transmits a voltage signal to gas generator pellets in air bag modules. The voltage signal ignites gas generator pellets to produce a quantity of non-toxic nitrogen gas.

In the air bag modules, the nitrogen gas passes through a tiny filter to fill and deploy the air bags in about 30 milliseconds. After the air bags inflate to maximum expansion, the nitrogen gas is released away from driver through 2 ventilation holes in rear of air bag. The air bag inflation and collapse sequence takes about 30-35 milliseconds.

In the Emergency Tensioning Retractor (ETR) seat belt assembly, the ignited nitrogen gas forces a piston to be driven downward in a tube attached to seat belt assembly. Piston has a cable attached to it. Cable pulls on seat belt reel, increasing seat belt tension and holding front seat occupant(s) tightly against seat backrest.