For the calculation of the performance parameters of combustion processes, equilibrium thermodynamic processes are taken into account. On the other hand, non-equilibrium reactions occur, mostly connected with low pressure burning. In this paper, several explosives, explosive mixtures, solid and liquid propellants have been calculated. It is shown how energy output and gas formation depend on the oxygen balance and the enthalpy of formation. It was found that the reason for the higher specific energy of liquid propellants is due to the increased formation of gases consisting of H-2, N-2 and H2O, compared with conventional solid propellants based on nitrocellulose and nitroglycerin, which produce more CO and CO2. Non-equilibrium combustion of solid propellants was found at very low loading densities or pressures lower than I to 2 MPa. In this case, the reaction products measured by mass spectrometry, such as NO, N2O and HCN, are metastable and highly toxic, producing a much lower heat of explosion compared with equilibrium burning measured and calculated.