The United States Navy uses the catalyst HOPCALITE for removal of carbon monoxide and hydrogen from the enclosed atmosphere of its submarines. At temperatures higher than those required for CO and H2, HOPCALITE also catalyses the oxidation of many organic substances. In some cases, these reactions produce toxic byproducts and/or catalyst poisoning. The activity of HOPCALITE varies greatly toward seemingly similar species. This work presents a model for predicting the activity of HOPCALITE with a linear equation using simple physical and chemical properties of the reacting species. Many parameters were evaluated. The model uses only three parameters to fit the observed reactivities of 51 chemicals. A final correlation coefficient (r2) of 0.80 is achieved.