An industrial furnace or direct fired heater is an equipment used to provide heat for a process or can serve as reactor which provides heats of reaction. Fuel flows into the burner and is burnt with air provided from an air blower. There can be more than one burner in a particular furnace which can be arranged in cells which heat a particular set of tubes. The radiant section is where the tubes receive almost all its heat by radiation from the flame. The convection section is located above the radiant section where it is cooler to recover additional heat.