An industrial furnace, also known as a direct heater or a direct fired heater, is a device used to provide heat for an industrial process, typically higher than 400 degrees Celsius.[1] They are used to provide heat for a process or can serve as reactor which provides heats of reaction. Furnace designs vary as to its function, heating duty, type of fuel and method of introducing combustion air. Heat is generated by an industrial furnace by mixing fuel with air or oxygen, or from electrical energy. The residual heat will exit the furnace as flue gas.[1] These are designed as per international codes and standards the most common of which are ISO 13705 (Petroleum and natural gas industries — Fired heaters for general refinery service) / American Petroleum Institute (API) Standard 560 (Fired Heater for General Refinery Service). Types of industrial furnaces include batch ovens, metallurgical furnaces, vacuum furnaces, and solar furnaces. Industrial furnaces are used in applications such as chemical reactions, cremation, oil refining, and glasswork.