The present invention related to a pyrotechnic gas generator intended for motor vehicle safety, comprising a sealed housing (1), which contains: —at least one combustion chamber (C) containing a pyrotechnic charge (3), the combustion of which is initiated by an initiator (2) associated with the chamber; —at least one plenum chamber (T) for receiving the gases generated by the combustion of the charge (3) for removing them to the exterior, via at least one discharge aperture (10) formed in said housing (1). It is characterized in that said housing (1) also contains means (R) for temporarily storing at least some of the combustion gases.