Pyrotechnically actuated devices (PADs), such as pyrotechnic separators, pyro-cutters, and pyro-valves, use a pressure cartridge to generate high operating pressure. Generally, an initiator is used as the pressure cartridge, which ignites a propellant, such as zirconium/potassium perchlorate (ZPP), electrically and generates a high-pressure gas within a very short time of less than 0.5 ms. To accurately predict the performance of the PADs, a proper combustion model should be secured; closed bomb tests typically have been performed for this purpose. However, a combustion test has not been performed in a chamber with a very small volume (a few cubic centimeters). In this study, the combustion characteristics of ZPP charge in a small volume chamber based on a series of experiments and a mathematical model are investigated to obtain a precise analytical model of PADs. The pressure histories were measured experimentally in a cylindrical chamber with various volumes for four different ZPP charge masses. The experimental results show the tendencies of the peak pressure and steady pressure according to the initial volume and ZPP mass. The energy efficiency for each case is evaluated by a zero-dimensional analysis. The change of the energy efficiency with regard to the vessel volume and ZPP charging mass is analyzed.