Topics commonly taught in a general chemistry course can be used to calculate the quantity of carbon dioxide emitted into the atmosphere by various human activities. Each calculation begins with the balanced chemical equation for the reaction that produces the CO[subscript 2] gas. Stoichiometry, thermochemistry, the ideal gas law, and dimensional analysis are then used to determine the source's CO[subscript 2] emission factor. This factor expresses the quantity of gas emitted for a given quantity of activity of the source. In the examples discussed, the mass of carbon dioxide is expressed in terms of the mass of cement produced by a cement factory, the volume of gasoline consumed by an automobile, and the heat produced by burning natural gas. The carbon footprint of each source can be determined from its CO[subscript 2] emission factor. (Contains 3 figures and 2 tables.)