Recent experimental work by Hakoda et al. attempted to determine the G-value of OH radical in electron-beam irradiation of humid N-2 using the conversion of CO to CO2 to titrate OH. Kinetic modeling is used to simulate the experiment of Hakoda et al. in an attempt to determine the validity of their assumptions and the reason the observed G-value was higher than expected. The model predicts CO2 production that is roughly 25% lower than observed and OH production about 10% higher than concluded from experimental data. This apparent contradiction is resolved by understanding the detailed chemistry of the OH + CO reaction and the fate of the thermalized HOCO intermediate. Analysis of the reactions producing OH indicate that the sources of OH are significantly different in humid air than in humid N-2, and the G-value for OH is much higher in humid air than humid N-2.