Oxidation Catalysts typically reduce up to 85 percent of carbon monoxide (CO), up to 60 percent of hydrocarbons (HC) and up to 20 percent of particulate matter (PM) from the exhaust stream. An oxidation catalyst is ideal for equipment that works in indoor applications, confined spaces or highly populated areas. Unlike some after-treatment options, the oxidation catalyst can be used regardless of the level of sulfur in the fuel, although they are most effective with fuels that have sulfur content of 500ppm or less.