Pyrotechnic safety device for a vehicle

The device has a pyrotechnic initiator (4) connected to a gas generator (5). There is a mobile screen (22) interposed between the initiator and the gas generator, this screen occupying one of two positions, an armed position in which the hot gas produced by the initiator press against the generator and a security position in which the mobile screen blocks the passage of the initiator gas to the gas generator, with the movement from one position to the other controlled by an actuator.