Oxidation of C2HF5 (pentafluoroethane, R125) that has been extensively used as a refrigerant and fire suppressant agent was examined by weak flames in a micro flow reactor with a controlled temperature profile (MFR) for safety reasons. To investigate the oxidation process of a stoichiometric C2HF5/air mixture, species measurements for a stoichiometric C2HF5/air weak flame at the maximum wall temperatures of the reactor from 750 to 1400 K were conducted using a Fourier Transform Infrared Spectroscopy (FTIR). Measurement results showed that two-stage oxidation which consist of the consumption of C2HF5 and formation of C2F6 at the first stage and the reactions of C2F6 at the second stage. Computational results reproduced the observed two-stage oxidation of C2HF5/air mixture. Since CO remained at the exit of MFR even in the case of a maximum wall temperature at 1400 K, incomplete oxidation of the C2HF5/air mixture was suggested. Therefore, the weak flame structure at a much higher maximum wall temperature of 2000 K was investigated computationally. The results showed that three-staged complete oxidation of a C2HF5/air mixture. The three-stage oxidation consisted of the two-stage oxidation similar to that observed in the case of the maximum wall temperature of 1400 K and additional oxidation from CO to CO2. The latter slowly proceeded because H atom in the fuel was mostly and already consumed by HF formation in the first stage. (C) 2020 The Authors. Published by Elsevier Inc. on behalf of The Combustion Institute.