According to the chemical analysis, we found the inert substances of fossils in Longkou oil shale in China are mainly calcium carbonate (CaCO3) and quartz (SiO2). Their influence on the explosive characteristics of oil shale dust, through the macroscopic explosion experiments and microscopic analysis, was investigated. We found that CaCO3 has better explosion suppression effect than SiO2. There are two suppression effects during the oil shale dust explosion: adhesion and isolation of inert substances; inerting effect of carbon dioxide (CO2) generated from the complex reaction of CaCO3 and SiO2. Due to the existence of two suppression effects, the combustion of oil shale particles stops when the heat generated by the two combustion paths is less than the heat dissipated, i.e., the explosion either comes to an end or fails to occur. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.