Quenching limits of laminar axisymmetric inverse diffusion flames were measured. The flames were obtained by injecting various oxidizers into fuels. Burner inside diameters were 0.75, 1.53, 3.02, 4.56 and 10.1 mm. Oxygen mole fractions in nitrogen were 0.21, 0.3, 0.4 and 1. Fuels were methane, ethylene and propane. The flames were observed in a weak co-flow of fuel inside a glass chimney. The flames were ignited at relatively high oxidizer flow rates, after which the oxidizer flow was reduced until extinction. The flames had heat release rates at their quenching limits of 1-2 W, compared to 3 W for a typical normal flame limit. The quenching limits of inverse flames were found to scale with (X_(O2))~(-1.4), to be independent of burner diameter, and to be proportional to the fuel's quenching distance in premixed tests. The results may help assess the hazards of firefighter respirator leaks in underventilated fires.
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