Natural gas is sampled to balance plant or gathering systems and to determine its quality for custody transfer applications. Many contracts are written in such a manner to account for the quality of the gas. The quality of the gas is determined by the energy contained in it, which is measured in British Thermal Units or BTU’s. A gas chromatograph is typically used to identify individual components of the sample and their quantity, thus determining quality of the sample taken. How the sample was obtained, transported and analyzed is crucial to the accuracy required for custody transfer of this product