The Airbag That Does Not Need Electricity
I recently had another opportunity to cut up two older Volvo sedans. What is interesting about these cars is that they had Volvo's original seat-mounted, side impact airbag systems. From 1995 through model year 1997, the first Volvo seat airbags did not use electricity to deploy. These bags, referred to by Volvo engineers as their 'mechanical' airbags, deployed using a plunger-type mechanical deployment mechanism.
When struck on the side, the door would move inward. A rigid component inside the door would cause the door to crush into a small plunger mounted low along the outboard side of each front seat. Once punched in, this plunger would fire off a pyrotechnic powder charge, causing the blast that actually resulted in the seat airbag deploying.
Although 1995 to 1997 Volvo cars are not that prevalent, what is important to note is that if one is encountered, shutting down the 12-volt electrical system DOES NOT make these seat airbags any less likely to accidentally deploy. In fact, when I conduct airbag deployment demonstrations, I simply open the door, take a flathead axe, and strike the plunger. The seat airbag deploys with just a medium hard hit from my tool.
First image is how the interior trim will look normally. This is a 1997 Volvo 850 sedan.
Second image shows the SIPSbag cover removed, exposing the plunger actuator.