The present invention relates to a gas generator (1) for a safety system. This generator comprises an explosible change formed at least by a primary pyrotechnic compound, in a first chamber (10), initiated by at least one initiator (11) provided with a reinforcing charge and a secondary compound, in a second chamber (20) provided, in a first zone (30) close to said first chamber, with peripheral orifices (17) for discharging the gases and containing, in a second zone (40), said secondary compound. A means (70) forming an obstacle to the passage of the gases is 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.