Compare this to gas furnaces of the mid-20th century, which filled the air with toxic fumes ... reach in and touch the blower motor to see if it’s hot. If so, that indicates it tried to start ...

The blower motor pushes hot air from the heat exchanger through the home's ductwork. Cool air in the home is cycled back to the furnace through the air return duct. Repairing a gas valve costs ...