Abstract-Serious global environmental problems are created by carbon dioxide emission such as global warming. The effect of CO 2 emission on the environment can be evaluated by using Exergy. The degree of deviation of a system from the environmental state can be measured by Exergy. A system is deviating when its composition, pressure & temperature are different from those of the environment. The difference can be measured by the Exergy discharge of CO 2 .In this paper, the Exergy analyses were used as a quantitative method to compare the carbon dioxide emission on three hydrocarbon fuels, which were methane, ethylene and propane. The affect of flame temperature and excess air on the emission Exergy of CO 2 were studied.Results showed that is sensitive to excess air and flame temperature. Also results showed that the environmental impact of carbon dioxide (higher emission Exergy) increases with increasing the ratio of (C/H).