What is the function of a recirculation fan in a gas recirculation system?

The function of a recirculation fan in a gas recirculation system is integral to maintaining optimal operating conditions within the system. It operates primarily by drawing gas from the furnace and then discharging it back into the system. This circulation allows for a more controlled environment, which can enhance combustion efficiency and reduce emissions.

In gas recirculation systems, the process of returning some of the exhaust gas back to the combustion zone not only helps to reuse the energy already present in the system but also helps in managing temperature and concentration of pollutants. By recirculating the gas, the fan ensures that the system operates more efficiently and safely, stabilizing the combustion process.

The other options, such as exhausting gas to the atmosphere, cooling the gas, or filtering impurities, do not align with the primary role of a recirculation fan. Instead, the focus is on recirculating gases within the system to enhance combustion rather than releasing or modifying the exhaust in the ways described in those options.