Verifying the correct operation and accuracy of the Gas Chromatograph (GC) is an integral part of a custody transfer metering system, and involves ensuring the accuracy of the analyzer at the time of testing, as well as confirming that the GC performed properly during the periods between validations and assessing the likelihood of continued proper functioning until the next validation. Because the GC will be off line during much of a validation procedure, the validation should only be performed at a time when the composition of the gas flowing through the metering station is relatively stable