In this research by the Bureau of Mines, slightly lean ch4-o2-ar flames at 0.042 Atm with and without small amounts of the inhibitor cf3br were probed using molecular beam and mass spectrometric techniques. Ratios of product concentrations to reactant concentrations were formed and compared with the equilibrium constant for seven reactions--(1) h + o2 = oh + o, (2) o + h2 = oh + h, (3) oh + h2 = h2o + h, (4) oh + oh = h2o + o, (5) CO + oh = co2 + h, (6) br + hbr = br2 + h, and (7) h + hbr = h2 + br--to determine to what extent they may be considered balanced in various regions of the flame. With the possible exception of reaction 4, none of the reactions are completely balanced until maximum flame temperature is reached. Once the reactions become equilibrated, their balance is maintained as the temperature and radical concentrations fall off in the secondary reaction zone. Reaction 7, in inhibited flames, is balanced at relatively low temperatures, comparable to reaction 4. Reaction 6 was found not to balance in either the secondary or primary reaction zones. Radical decay in the secondary zone was analyzed using the pool-decay concept. The important recombination reactions were judged to be h + oh + m -> h2o + m and h + o2 + m-> ho2 + m. A rate coefficient of 2 x 10 16 cm6 mole-2 sec-1 is calculated for m = the burnt gas mixture of ar, h2o, co2; and 5 x 10 15 cm6 mole-2 sec-1 is calculated for m = ar (both for t = 1,750 +/- 150 k).