The explosion characteristics of chlorine dioxide gas have been studied for the first time in a cylindrical exploder with a shell capacity of 201.The experimental results have indicated that the lower concentration limit for the explosive decomposition of chlorine dioxide gas is 9.5% ([ClO2]/[airl),whereas there is no corresponding upper concentration limit.The maximum pressure of explosion relative to the initial pressure was measured as 0.024 MPa at 10% ClO2 and 0.641 MPa at 90% ClO2.The induction time (the time from the moment of sparking to explosion) at 10% ClO2 was 2195 ms,but at 90% ClO2 the induction time was just 8 ms.The explosion reaction mechanism of ClO2 is of a degenerate chain-branching type involving the formation of a stable intermediate (Cl2O3),from which the chain branching occurs.