Correlations have been developed that use chemical equilibrium considerations to predict the operation of bubble-cap columns using hyperazeo-tropic nitric acid (Iodox system) to treat air streams containing I2 or CH3I. The error in predicting decontamination factors (DFs) by the developed equations is on the same order as the uncertainty in the DFs determined in experimental tests. Methyl iodide is trapped less efficiently than molecular iodine; this effect is explained by the lower distribution of methyl iodide to concentrated nitric acid from air. The presence of NO2 in the gas stream was calculated to cause a reduction in the DF for the first few stages, but with little effect on later stages.