Pt catalysts compared to hopcalite for Naval submarine pollution control. All catalysts exhibited low-temperature combustion of CO in dry air streams. Hopcalite was deactivated by presence of humidity; Pt catalysts were activated. Pt/CeO2 performed less HCFC oxidation than Pt/Al2O3 or hopcalite/LiOH. Pt outperforms hopcalite and should be considered for replacement.