A gas generator for a safety system includes an explosible charge formed at least by a primary pyrotechnic compound, in a first chamber initiated by at least one initiator provided with a reinforcing charge and a secondary compound, in a second chamber, the decomposition of which is entailed by products of combustion of the primary compound, an interaction of the products of combustion of the primary compound and those of the secondary compound through an oxidation-reduction reaction occurring in a slightly confined volume, the first chamber communicating with said second chamber through a central nozzle and said second chamber being provided, at a first zone close to said first chamber, with orifices that discharge the gases and contain, in a second zone, said secondary compound; and means forming an obstacle to the passage of the gases installed in said second chamber between said first and second zones, said obstacle-forming means allowing the gases to pass into a central part and forming an obstacle to their passage into a peripheral part with sufficient transparency for the gas interaction volume to be slightly confined.