The objective of OPAS SO2LH notification service is to provide SO2LH information in NRT. The SO2LH characterises the effective plume height of the SO2 layer related to a volcanic eruption. Note that the SO2 is a proxy for sulphide emissions, which can induce sulphidation inside engines and potentially conduct to an accident caused by engine failure and damage. The SO2LH is also a proxy for the volcanic ash height, which is notoriously difficult to measure. The SO2LH information are currently provided by 3 instruments (TROPOMI and IASI) respectively on board S5P, MetOp-A & MetOp-B POLAR_OPERATIONAL_ENVIRONMENTAL_SATELLITE.