Inhibition of Diffusion Flames by Methyl Bromide and Trifluoromethyl Bromide Applied to the Fuel and Oxygen Sides of the Reaction Zone

The difference in extinguishing effectiveness of an inhibitor introduced on the two sides of the reaction zone of diffusion flames has been measured as a function of oxygen concentration in the O(2)-N(2) mixture supplied to the flames. Six fuels and two inhibitors were used. It was found that when the inhibitor was added to the fuel, the volume percentage required for extinguishment was much greater than when added to the oxygen side of the reaction zone, with the single exception of CO flames inhibited by trifluoromethyl bromide. In all cases except the latter, the amount required for extinction increased with increase of the oxygen concentration, being relatively less dependent on oxygen concentration above a certain threshold in the neighborhood of 21 percent when the inhibitor was added to the fuel. Above oxygen concentrations on the order of 25 percent, methyl bromide was completely ineffective when added to the oxygen side of the reaction zone, and above about 32 percent oxygen it was ineffective when added to the fuel, since at this oxygen concentration it burns without additional fuel.