Side Impact Head Protection System (HPS)
WARNING: This page is about a different car, the 2001 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
HPS consists of air bag modules which are installed along both A-pillars, over front doors and extend slightly beyond B-pillar. Air bag modules are also installed in C-pillars and extend over rear doors. They provide additional protection for the front and rear passenger in the event of a severe side impact.
HPS module consists of an inflatable tube-shaped air bag, gas generator, and igniter. Air bag fully inflates in about 35 milliseconds. Gas is then released through a filtered vent causing it to deflate.