Fired heaters are used to provide heat through the combustion of fuel. They involve combustion fundamentals like the reaction of methane and oxygen. Fired heaters have a furnace design and use draft systems and air preheaters. They employ different types of burners like those used in hot oil heaters and regeneration gas heaters. The start-up process involves inspection, purging, lighting pilots and burners, and adjusting temperatures and flows. Operation requires monitoring air adjustment, temperatures, and addressing potential issues like deposits, failures, or flame-outs. Control strategies manage variables like temperatures, fuels, and flows.