What component in a furnace is responsible for shutting it down for safety?

The thermocouple is a critical safety device in a furnace system. Its primary function is to monitor the presence of a flame. When the furnace is operating, the thermocouple generates a small voltage based on the temperature from the flame. If the flame is extinguished for any reason, the voltage will drop, leading to the closure of the gas valve. This action prevents unburned gas from accumulating, which enhances safety by reducing the risk of gas leaks and potential explosions.

The pilot serves to ignite the gas in the furnace but isn’t responsible for the safety shutdown process directly. The gas valve controls the flow of gas to the burners, but it relies on signals from components like the thermocouple to open and close safely. The thermostat regulates the temperature in the environment but does not inherently shut down the furnace for safety reasons; it functions more to control the operation based on temperature settings rather than responding to flame presence or safety conditions.