I suggest you to consult a textbook of physico-chemical properties or a thermodynamic textbook. Some of then you will find in the internet. One good textbook is the Poling, Prausnitz and O' Connel book named: "The properties of gases and liquids" of Pouling
Rich, sorry I also made a mistake. I never saw critical properties for OH, O or H but only for H2, O2 or water, they are easily found. But let me make a question, why do you need these infos? Are you sure they are not H2, O2 and water? Because normally we use these properties to estimate gas mixtures not ionized ( in fact H will be H1+, O means O-2 and OH is OH-, all in the form of ionized gases).