The Advanced Fired Heater is a gas-fired process heater that uses both forced draft and induced draft fans to provide air to and exhaust flue gas from the heater firebox. The heater is outfitted with a rotating element air preheater. The heater may also be run in natural draft mode at a reduced capacity in case either fan is out of service. In this mode, the air preheater is bypassed, and combustion air is admitted directly from atmosphere into the combustion air plenum using natural draft. The system includes a typical firing control scheme to safely manage fuel gas and combustion air flows to meet process fluid outlet temperature requirements. The heater is also outfitted with protective interlocks to prevent unsafe operation of the unit.