Gas generator

The gas generator has a burner chamber (25) with pyrotechnical propellant charge (26) pre-stressed with a pretension unit (50) which is held in a predetermined secured compressed position through a releasable holder unit so that the pretension unit can be selectively released to move into a release position where it exerts a pretensioning force on the propellant charge. The holder unit has a mechanical lock e.g. projections (58).