Three types of rubber waste (soft, hard with fibers or steel elements) were combusted sep. in a lab. quartz reactor (diam. 98 mm, height 500 mm) at 600-800 degrees C by using a sand (grain size 0.35-0.40 mm) as a bed and air as a fluidizing agent to det. the effect of combustion temp. and a mass of the used sample on the reaction time. Furthermore, the exptL results were compared with the estd. values based on the shrink core model. An increase of the reactor temp. and the decrease of the mass sample resulted in shortening the time of the sample destruction. The tested calcn. model did not adequately describe the relation studied.