Thermal fluid heating, sometimes referred to as thermal oil heating, is a type of indirect heating in which a liquid phase heat transfer medium is heated and circulated to one or more heat energy users within a closed loop system. Thermal fluids offer the user the capability of high temperature operation (up to 600F with organic thermal oils and 800F with certain synthetics) at very low pressures. Due to the low operating pressure and properties of thermal oils, most heaters are built to ASME Section VIII, and a licensed boiler operator is not typically required