Abstract: A gas-fired humidifier includes a heat exchanger with a plurality of generally upwardly extending tubes. These are connected at their lower ends to a source of water and at their upper ends to a steam header. A gas-fired burner is arranged to direct heat to the exterior of the tubes so as to cause water therein to boil and form steam in the steam header.

Abstract: The water heater includes a water tank, a burner below the tank, a casing around the outside surface of the tank and spaced therefrom so as to define a flue path within the casing and along the outside surface of the tank for combustion products. Multiple flow restrictions are located in the flue path and extending inwardly from the casing towards the outside surface of the tank and forming regions of restricted flow area so that the combustion products flowing along the flue path encounter the flow restrictions and are restricted and disturbed in flow pattern. The first flow restriction which is first encountered by the combustion products is located at a position along the height of the tank no lower than one third of the overall height of the tank up from the bottom of the tank whereby the lower portion of the tank over which combustion products are flowing are substantially completely exposed to the hottest and most turbulent combustion gases.

Abstract: A header for a heat exchanger having a plurality of parallel hollow tubes mounted between a pair of flat mounting plates and defining a plurality of passages through the plates. The header comprises a tubular elongated body portion having an outer surface and an interior cavity. The body portion is provided with a plurality of parallel, hollow ports projecting from the outer surface to provide fluid communication between the passages and the cavity. The projecting ports space the header from the tube plate so that the header body remains relatively cool. This permits the header to be made from a plastic material.