In systems like steam boilers and thermal oil heaters, this induced draft fan creates a vacuum of negative air pressure to pull out and remove exhaust gasses from combustion chambers. A blower is used to draw air into the combustion chamber and the rest of the system, and afterwards a chimney or stack is used to expel the air and flue gas. This induced draft fan can handle a lot of hot, low-density air, which raises maintenance and operating costs.