To provide a reduction method of NOx generation amount in operating a hybrid inflator.

This reduction method of nitrogen oxide generated in operating the hybrid inflator for an inflation type safety system for a vehicle having an air bag is provided with an inflator housing filled with pressure medium, a gas generator stored in the inflator housing and having one, two, or more gas generation chambers storing gas generating agent including fuel and oxidizer, and an air bag having an ignition means connected to the gas generator. This reduction method for nitrogen oxides of the hybrid inflator is disposed with reducing compound having, at least, a reducing function of the nitrogen oxide in the hybrid inflator.