Environmental protection laws like EPA’s Clean Air Act, industry standards, end user specifications, and engineering and social responsibility have been drivers to reduce emissions in valves. API 622, 624, and 641, as well as ISO 15848-1 and -2 will be reviewed and compared, with specific attention given the design parameters that must be considered and controlled to reduce volatile organic compound emissions. Application to other non-hydrocarbon processes will also be addressed. With this better understanding, engineers and purchasers will learn how to specify and low emission valves.