A thermal oil heater is a new type of special boiler with low pressure and high-temperature operating characteristics, capable of reaching heating temperatures of up to 340°C in the liquid phase or 400°C in the vapor phase. Organic thermal fluid heating can be used in various production environments where a uniform and stable heating is required, and direct flame heating is not permitted, within the temperature range of 150°C to 380°C. The thermal oil heater, fueled by gas, uses thermal oil as the medium and employs a circulating oil pump to force the medium into a liquid phase circulation, transferring heat to the heat-using equipment and then returning it to the heater for reheating. It can achieve high working temperatures at low pressure and offers high-precision control of the medium's operation. The system has a high thermal utilization rate, and due to its modular overall installation, it is easy to operate and maintain, making it an ideal and energy-efficient heating equipment. The high-temperature flame produced by the fuel oil (gas) burner enters the inner coil to form a radiant heating surface. After passing through the rear of the inner coil, it rotates 180° forward into the annular space between the inner and outer tubes to form a convective heating surface. Then, it enters the second annular space above the middle and outer coils, and finally, it is discharged into the atmosphere through the chimney at the rear of the second annular space.