The LR111-D300 model aerosol LIDAR is an active laser remote sensing instrument, designed to provide a wealth of information about the atmosphere, including unambiguous detection of volcanic ash. It can also provide detailed information on the Planetary Boundary Layer (PBL), including information for air quality and forecasting model validation. With a minor upgrade, the system can provide remote humidity profiling (dusk-dawn only). Raymetrics has been building Raman depolarization LIDARs since 2004. However the final specifications of the LR111-D300 model LIDAR were determined according to Met Office (UK) and EARLINET (European LIDAR Network) requirements. A large telescope and powerful laser make the LR111-D300 probably the most powerful eye-safe aerosol LIDAR available commercially.