Abstract: An apparatus and a method for preventing fire in a liquid heating tank that utilizes resistive heating elements for raising the temperature of a flammable liquid are described. In the apparatus, a buffer tank is provided which is positioned under a process tank that heats the flammable liquid. The buffer tank is equipped with a thermocouple for detecting the temperature of fluid flown therein and an air actuated solenoid valve for shutting off a drain pipe from the buffer tank. When a higher temperature is sensed by the thermocouple, i.e. caused by the mixing of the higher temperature process liquid and the lower temperature water, the air solenoid valve is shut off to cause a back flow of the processed liquid/water mixture into the process tank and thus keeping the heating elements submerged in the processed liquid/water mixture. Any possible exposure of a hot surface of the resistive heating elements to ignite flammable vapor or liquid is thus prevented and a potential fire is avoided.