Since the 1950's US submarines have employed a heated catalytic oxidizer to remove trace contaminants and hydrogen from their atmosphere. A copper oxide-manganese oxide catalyst, Hopcalite® , is the traditional material for this application. In the late 1990's the United States supplier ceased production of this catalyst. This paper describes the Navy's efforts to qualify new catalyst and to establish a new performance based specification. Results of land based and shipboard testing are summarized.