An experimental study is conducted to evaluate the effectiveness of sodium bicarbonate (NaHCO3) powder in extinguishing flames burning hydrocarbon fuels. Experiments are performed on flames stabilized in a counterflow burner. Powders with various particle sizes are used. The minimum amount of NaHC03powder required to extinguish these flames is measured and compared with previous measurements using CF3Br and N2. The results show NaHCO3, to be much more effective than CF3Br and N2, in extinguishing the flames. The calculated equilibrium temperatures of NaHCO3inhibited flames close to extinction show that NaHCO3, inhibits the flame by chemical mechanisms.