The effect of adding 20–50 % H2 to active nitrogen has been studied at 196 and 320° K. At neither temperature is there a primary reaction but when the nitrogen atoms are partially titrated with nitric oxide at 320° K, a catalytic removal of atoms is induced involving the reactions : O + H2= OH + H (5), N + OH = NO + H (8), N + NO = N2+ O (1), O + OH = O2+ H (9), with (5) rate controlling. The consumption of both nitrogen atoms and oxygen atoms was followed photometrically and the results yields a ration k8/k9– 1.4±0.1 at 320° K. The rate constant k5 was (1.2 × 0.1)× 107cm3 mole –1 sec–1at 320° K in separate experiments. The role of H2 as a third body in the recombination reactions of nitrogen and oxygen atoms has been examined at 196° K where reaction (5) is unimportant.