From the IR induced spectrum between 4000 and 5000 cm(1) of solid normal hydrogen doped with H2O, CH3F, CH4, and double doped with O-2, the nuclear spin conversion of ortho-H-2 molecules has been analyzed at 4.2 K. The self-conversion rate is determined to be K-sc = 2.8(3) x 10(4) min(1), with no implication of O-2 atmospheric impurity. Within the framework of an ortho-H-2 diffusion dominated process, the O-2 catalyzed conversion rate is deduced to be K-cc = 0.17(3) min(1). We have shown that CH3F induces ortho-H-2 conversion at the same rate as O-2, according to a diffusion controlled process, via intra-cluster conversion. (C) 2009 Elsevier B. V. All rights reserved.