An apparatus for protecting a vehicle occupant that triggers a restraint means as a function of the vehicle occupant’s motion in the context of an accident. In a pneumatic circuit, a check valve and a throttle valve are connected in parallel in each of first and second pipes connecting first and second ports of the cylinder and a solenoid valve and a check valve and a throttle valve are connected in parallel in a third pipe connecting the third port and the first pipe or the second pipe. In other embodiments, the platform may be supported by ribbed concrete panels. A first frangible membrane extends across the entrance port and separates the reservoir from the gas chamber.