Explosion test systems for determining explosibility indicies (Kst) of certain dust and gaseous fuels are provided. The test systems comprise a combustion vessel (130) and associated control equipment (110) containing software for operating the combustion vessel and collecting data generated thereby. The combustion vessel (130) generally comprises a test chamber (140) and a reservoir module (150) operable to inject a fuel into the test chamber, wherein an ignition module (170) ignites the fuel.