Quenching limits of hydrogen diffusion flames on small burners were observed. Four burner types,with diameters as small as 8 m, were considered: pinhole burners, curved-wall pinhole burners, tubeburners, and leaky fittings. In terms of mass flow rate, hydrogen had a lower quenching limit and a higherblowoff limit than either methane or propane. Hydrogen flames at their quenching limits were the weakest