We investigated the effects of different metal oxide (MO) nanoparticles (e.g., CuO, KIO4, Fe2O3) on the combustion and gas-generating characteristics of sodium azide microparticle (NaN3 MP; gas-generating agent) and aluminum nanoparticle (Al NP; heat source) composite powders. The NaN3 MP/Al NP/MO NP composite powders were stably ignited using a microhotplate (MHP) heater. The addition of CuO and KIO4 to the NaN3 MP/Al NP composite powders resulted in relatively high burn rates and high pressurization rates upon MHP-assisted ignition. This suggests that the highly reactive CuO and KIO4 NPs significantly increased the combustion of the Al NPs; as a result, sufficient heat energy was generated via the active aluminothermic reaction to thermally decompose the NaN3 MPs. Finally, the gas generating properties of NaN3 MP/Al NP composite powders mixed with various MO NPs were tested using home-made inflatable small airbags. The airbags were fully inflated within similar to 20 ms when CuO and KIO4 NPs were added to the NaN3 MP/Al NP composite powders. However, the addition of Fe2O3 NPs to the NaN3 MP/Al NP composite powder resulted in a slow and only partial inflation of the airbag due to an incomplete aluminothermic reaction, which was due to a slow combustion reaction between the Al NPs and relatively weak oxidizer of the Fe2O3 NPs. This suggests that the rapid, stable, and complete thermal decomposition of NaN3 MP/Al NP composites can be effectively achieved by employing highly reactive nanoscale oxidizers. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.