This part of ISO 4266 gives guidance on the accuracy, installation, commissioning, calibration and verification of automatic level gauges (ALGs), of both intrusive and non-intrusive types, for measuring the level of petroleum and petroleum products having a Reid vapour pressure less than 100 kPa, stored in atmospheric storage tanks. This part of ISO 4266 is not applicable to the measurement of level in refrigerated storage tanks with ALG equipment.