Carbon monoxide (CO) is emitted from gas turbines and other combustion devices from incomplete combustion. Incomplete combustion can occur when there is too much fuel or not enough air in the combustion process. Incomplete combustion can also occur from insufficient fuel and air mixing, and excessively low combustion temperatures. Smoke is a sign of incomplete combustion. Carbon monoxide (CO) forms instead of carbon dioxide (CO 2) in incomplete combustion.

The CO catalyst is similar to the catalyst used for selective catalytic reduction and is often made with a honeycomb structure or parallel plates. The active element that oxidizes the carbon monoxide is a precious metal such as platinum. The catalyst is often applied as a coating over the catalyst structure. In order to withstand the high temperatures downstream of the turbine the catalyst structure is made with a ceramic material. In some ways, the CO catalyst is very similar to a catalytic converter on a car.