[en] A detailed comparison is made with the predictions of the hydrodynamic steady state theory of hot atom reactions developed by Keizer [J. Chem. Phys. 58, 4524 (1973)] and those obtained from a more precise moment method solution of the Boltzmann equation. Agreement is found to occur only if there is a good separation in the time scale for reactive collisions and the time scale for energy redistribution in elastic collisions. This requires that the system parameters, which includes mass ratios and cross sections, be such that the reaction proceeds slowly relative to the rate of elastic collisions. The steady state theory was intended to be a qualitative theory of hot atom reactions and fulfills that expectation for systems that possess the neccesary separation in relaxation times