Mechanically-induced combustion reactions were carried out in a transparent quartz vial. The combustion processes were followed by high-speed video recording and optical pyrometers. Depending on the vial dynamics, the powder particles were seen to gather in a periodic collective motion, behaving like a granular gas characterised by subsequent changes in its density. After ignition, a considerable increase of brightness was observed, due to the extremely rapid propagation of the high-temperature reaction to the whole mass of powder. Experimental observations find a very good correlation if compared to the results of numerical calculations simulating the particle system dynamics. Balls and powder dynamics were reproduced according to a well-known visco-elastic force scheme, while chemical conversion of each powder particle was described by a conventional nucleation-and-growth kinetics. The propagation mechanism of the reaction was studied and related to the dynamic features of the whole system. (C) 2004 Kluwer Academic Publishers.