Fixed storage tanks at atmospheric pressure or under pressure (hereinafter called “tanks”) are built for bulk liquid storage and may be used for the measurement of quantities (volume or mass) of liquid contained. When used for that measurement, they shall comply with the requirements of this Recommendation. 2.2 In addition to the requirements for parts of the tank, such as the gauging hatch and datum plate, the calibration table should be accurately determined as it is a component of the measurement of quantity (volume or mass) of liquid in the tank. 2.3 This Recommendation specifies the general requirements for all stationary storage tanks onshore with fixed or floating roofs including pressured, non-pressured, refrigerated and non refrigerated tanks. Additional information for the different types of tanks is stated in clause 9.