Calibration standard gases are essential to quantitative analytical measurements in petrochemical processes, natural gas, environmental compliance, and health and safety programs. The calibration gas standard establishes a known analyzer response to a certified chemical component concentration which enables the conversion of sample responses to a concentration with a determinable accuracy. In consideration of the criticality of calibration standard gases to valid measurements in chemical processes and monitoring programs, the objective of this paper will be to provide an in-depth review of how calibration standard gases are manufactured, certified, and properly maintained