Since fuel dispensers are the focal point of distributing fuel to the general public, and fuel is a hazardous substance, they are subject to stringent requirements regarding safety, accuracy and security. The exact details differ between countries and can depend to some extent on politics. For example in countries fighting corruption, such as Mexico, gas pumps may be more stringently monitored by government officials, in order to detect attempts to defraud customers. Typically, individual pumps must be certified for operation after installation by a government weights and measures inspector, who tests that the pump displays the same amount that it dispenses. Measurement Canada is the federal agent responsible for pump regulations in Canada and stickers are displayed on the pumps. Hydrogen fuel dispensers are regulated under SAE Standard (J2601). https://en.wikipedia.org/wiki/Fuel_dispenser