The R-15 oxygen generator provides on-demand oxygen delivered to the subject using an oxygen facemask. The R-15 oxygen generator consists of housing containing the oxygen generating chemical in mesh pouches, reaction regulating sealed liquid containing pouches, a lid, a water bag and a valve assembly with a compartment for the catalyst. The oxygen producing chemical, catalyst and water are isolated from each other during storage by placing each in separated sealed compartments. The compartments are connected by a valve that upon activation allows the water to flow through a chamber in the valve containing the catalyst and into the compartment in the housing with the mixture. The water distributes the catalyst through the compartment and submerses the oxygen generating chemical mixture and a portion of the sealed pouches. When the hydrogen peroxide contacts MnO2, the hydrogen peroxide is decomposed catalytically to water and oxygen.