Research and development studies concerning the combustion and the behavior of the various materials encountered in nuclear reactors and facilities are carried out by the CEA in "fire laboratories" at CADARACHE. The objective is to place qualified numerical and technical tools at the disposal of designers, project managers and safety analysts. Qualification is supported by experiments and physico-chemical models. Results are given on pyrophoric metals (mainly magnesium) and carbon compounds (inflammable liquid and solid) combustion and on fire extinguishing procedure.