Diesel oxidation catalysts are one of the aftertreatment products available from Empire Emissions Solutions to lower emissions from the in-use population of diesel engines. A diesel oxidation catalyst (DOC) is an aftertreatment device employed to reduce CO, HC, and the soluble organic fraction (SOF) of PM. They are relatively small and inexpensive. Oxidation catalysts are typically sized to replace the existing muffler and do not require any maintenance. They reduce PM by about 20% (this percentage depends on how much of the total PM is attributable to SOF) and are very efficient at reducing CO and HC, with efficiencies of about 85% and 60%, respectively. They do not reduce NOx.

In addition to Caterpillar's extensive experience with the development of oxidation catalysts for new on-highway engines, hundreds of in-use machines have been retrofitted with this technology. Caterpillar refers to DOCs that replace the existing muffler as Catalyzed Converter/Mufflers (CCM). Caterpillar® CCMs are available for over 160 Caterpillar machine models.