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A gas forced-air heating system has a pilot light that ignites a burner inside the combustion chamber, creating heat that is then transferred to the furnace’s heat exchanger, a metal chamber around which air flows and is then heated. That heated air is then forced into the hot-air plenum and into the rooms through ducts. Gas fumes and carbon monoxide are vented through a flue in the roof. The forced air gas furnace provides the option for an attached air conditioning unit and humidifier. A gas forced-air heating system has a pilot light that ignites a burner inside the combustion chamber, creating heat that is then transferred to the furnace’s heat exchanger, a metal chamber around which air flows and is then heated. That heated air is then forced into the hot-air plenum and into the rooms through ducts. Gas fumes and carbon monoxide are vented through a flue in the roof. The forced air gas furnace provides the option for an attached air conditioning unit and humidifier, part of a complete central air HVAC (Heating, Ventilating, and Air Conditioning) system.