The calculations of enthalpies and free energies for various monomolecular decompositions of sulfur mustard using G2(MP2) theory have shown that noncatalytic thermal destruction of this chemical warfare agent apparently is not feasible at temperatures up to 1800 K at least. Environmentally robust decomposition/ destruction demands operating conditions in excess of 2000 K to insure intrinsic safety in the absence of a catalyst. The preferable decomposition pathways involve C-C and C-S bond cleavages. The G2(MP2)calculated enthalpy of formation of sulfur mustard is -36.86 kcal/mol for the lowest energy C-2 conformation.