The intensity of air afterglow chemiluminescence in N2 carrier has been used to investigate the flow patterns within a diffusion-stirred flow reaction sphere with in-line and non-penetrating entry and exit tubings. Photometric measurements of intensities at entry and exit observation stations have been inter-calibrated under high linear flow rate conditions. Consequently rate constant data for O(3P) atom reactions are obtained directly from the relative entry and exit intensities measured under the diffusion-stirred flow operation of the sphere at lower volume flowrates. Rate constants for H(2S) atoms are also measured, the latter generated in situ from O(3P) atoms by the reactions O + H2→ OH + H (1), O + OH → O2+ H, (2), using the air afterglow chemiluminescence associated with O + NO + M → NO2+ M. (3), When NO is present in the O + H2 system, the reaction H + NO + M → HNO + M (4), catalyses the removal of O atoms through the subsequent reaction O + HNO → OH + NO. (5), It is shown that k5 > 100 k6 for T⩽ 425 K where H + HNO → H2+ NO. (6), Values of k4 for M = Ar and N2 in the range 360–425 K are measured; relative efficiencies of N2: Ar =(1.64 ± 0.12): 1.0 are derived. No evidence for significant occurrence of reaction (7), OH + HNO → H2O + NO (7), was found. An upper limit of k7/k5⩽ 4.4 is derived for T⩽ 425 K using literature limits for k6 and k7. Arrhenius expressions k1=(3.1 ± 0.5)× 1010 exp (–4950 ± 300 K/T) dm3 mol–1 s–1(363 K < T < 490 K) and k3=(1.8 ± 0.5)× 109 exp (+900 ± 85 K/T) dm6 mol–2 s–1(M = N2)(285 K < T < 432 K) were also obtained, together with a relative efficiency of N2: Ar =(1.62 ± 0.14): 1.0 in reaction (3), all in good agreement with the literature.