Quantifying Post‐Exotherm Molar Gas Yields From Thermal Decomposition of CHNO High Explosives for Compatibility and Pressure‐Screening Calculations

To inform safety and compatibility calculations, we measured the total post‐exotherm molar gas yield following thermal decomposition of PETN, RDX, HMX, LLM‐105, and TATB in an accelerating rate calorimeter (ARC). The measured yields, which span 22.0–32.4 mol , provide a basis for estimating decomposition extent from evolved‐gas measurements and serve as critical input for the approximation of high‐ullage vessel pressures following thermal decomposition of a CHNO material. For all five compounds, the measurements were within 10% of Cheetah thermochemical‐equilibrium predictions after the predicted water contribution was excluded, which is consistent with water condensation in cooler portions of the apparatus. The Cheetah‐estimated values also agree with a simple stoichiometry‐based calculation, enabling a survey of predicted gas yields of 1,454 CHNO compounds. For the chemical reactivity test (CRT) criterion of 0.75 , the evolved gas corresponds to approximately 0.10%–0.15% of the measured post‐exotherm gas yield. Expressing CRT and related gas‐evolution measurements, such as vacuum stability, on this common basis helps connect legacy data to kinetic models and complementary compatibility techniques such as heat‐flow calorimetry.