Heating Cooling Unit (HCU) is an environmental conditioning unit that is designed in accordance with relative standards, using vapour compression cycle to condition temperature of marine laser systems. ISB with different modes that are heating, cooling and circulation, has its own microcontroller to switch on modes according to ambient and circulation liquid temperature. Thus, laser system temperature will be optimum in any ambient conditions. ISB that is designed for marine conditions, is qualified by MIL-STD-810G and MIL-STD-461F.