Slow reaction and explosions of n -pentane-oxygen mixtures have been studied in the low-temperature range. The apparatus permits pressure measurements and local gas-temperature recordings at different points of a spherical reaction vessel. Various inerts have been added (He, Ar, N 2 , CO 2 ) in a wide range of concentrations (14% to 90%). We have determined cool-flame limits, maximum temperature rise for the slow reaction, and critical temperature rise for cool flames along a diameter of the reaction vessel. The experimental results are expressed as functions of the physical parameters which represent the thermal properties of the mixture, mainly thermal conductivity and heat capacity.