Temp., d. and chem. compn. of the gas generated by decompn. of a solid mixt. of cellulose and glycerol nitrates were calcd. by direct Monte-Carlo simulation and then by using conventional equations of gas dynamics. Results of the calcns were confirmed with resp. expil. data. Cooling the decompn. chamber walls was recommended for controlling the gas pressure For the calcn., an original computer program was written in FORTRAN 77 under operating LINUX system.