Abstract: An improved heating system is disclosed for providing heated air to a heated space, preferably using a gaseous fuel as the energy source. The system preferably includes an air heating sub-system, a compact combustion chamber, a separate cold air supply sub-system for conveying cold air from the heated space to the air heating sub-system, a combustion chamber heat exchanger in fluid communication with the cold air supply sub-system for transferring heat thereto, and a separate air circulating sub-system for withdrawing cold circulating air from the heated space. A mixing chamber is provided for mixing heated air from the air heating sub-system with the cold circulating air to provide heated air to the space. The system also preferably includes separate sub-systems for supplying pressurized combustion air and pressurized gaseous fuel to the air heating sub-system and for forcibly conveying exhaust gases therefrom without the need for a draft-type chimney or stack.