The effect of CO2 on the emission characteristics of Spindt-type molybdenum field emission cathode arrays is investigated. Exposure of active field emitters to CO2 results in emission degradation. The degradation ranges from (11.8 +/- 3.8)% for 10 L to (77.2 +/- 12.6)% for 5000 L CO2 exposures. The emission loss results from the formation of molybdenum oxide on tip surfaces, resulting in an increased work function. Work function changes of 0%-7.5% have been measured. The emission changes resulting from CO2 exposures are similar to the effects observed with O-2 exposures. The emission degradation mechanism is the interaction of oxygen with molybdenum forming surface molybdenum oxides, thus resulting in a higher surface work function and lower emission current. The emission degradation resulting from CO2 exposure is compared to the emission enhancement produced by exposure to CH4.