Lean flame extinction limits of binary fuel mixtures of methane (CH(sub 4)), propane (C(sub 3)H(sub 8)), and ethane (C(sub 2)H(sub 6)) were measured using a twin-flame counter-flow burner. Experiments were conducted to generate an extinction equivalence ratio vs. global stretch rate plot and an extrapolation method was used to calculate the equivalence ratio corresponding to an experimentally unattainable zero-stretch condition. The foregoing gases were selected because they are the primary constitutes of natural gas, which is the primary focus of the present study. To validate the experimental setup and methodology, the flame extinction limit of pure fuels at zero stretch conditions were also estimated and compared with published values.