Abstract: An apparatus provides improvement over the apparatus that provides a highly humid air into a boiler or internal combustion engine such as diesel, gasoline, and other similar engines, and improves the fuel economy and reduces the amount of the produced exhaust gases from the boiler, etc. by adding the highly humid air into the suction pipe through which it is delivered into the combustion chamber together with the mixture of the injected fuel gas and air. The highly humid air provided by the improved apparatus contains a mixture of vaporized water flow drawn by suction under the reduced pressure developed within the combustion chamber and an air flow drawn from the atmosphere, the mixture being formed by allowing the two flows to meet together and strike against each other at angles of 55 to 65 degrees.