Calorific value (CV) is a measure of heating power and is dependent upon the composition of the gas. The CV refers to the amount of energy released when a known volume of gas is completely combusted under specified conditions. The CV of gas, which is dry, gross and measured at standard conditions of temperature and pressure, is usually quoted in megajoules per cubic meter (MJ/m3). Knowledge of the CV of natural gas is an essential part of a transmission system’s activities as this information is used to determine the amount of energy transported and thus CV information is usually provided daily to gas shippers and suppliers, which is then used to bill gas consumers. The data is also used to determine transportation charges for gas shippers and suppliers. The CV of natural gas is measured continually using process gas chromatographs. Process gas chromatographs separate natural gas into its constituent compounds (i.e. methane, ethane, carbon dioxide, etc.) and measure the amount of each in the gas.