Propane is available as part of various specialty gas mixtures, including two-component and multi-component gas mixtures. Propane is used in many hydrocarbon chromatographic standards, such as ASTM blends and hydrocarbon gas mixtures, as well as in natural gas and liquid standards, including calorimetric, high-ethane, extended analysis, GPA, helium and pipeline. All of these are used in the oil and gas industry. Propane gas mixtures are also used as span gas calibration mixtures in engine emissions testing in the automotive industry, and are ISO 17025 accredited and Part 86 compliant. Other propane gas mixtures are used in environmental, industrial hygiene and safety, and laboratory applications.