This document gives requirements and guidance on the accuracy, installation, commissioning, calibration and verification of automatic level gauges (ALGs). It applies to ALGs which are both intrusive and non-intrusive types, in fiscal/custody transfer applications for measuring the level of petroleum and petroleum products having a Reid vapour pressure less than 100 kPa, stored in atmospheric storage tanks. This document is not applicable to the measurement of level in refrigerated storage tanks with ALG equipment.