Condensing, ultra-low NOx gas-fired humidifier

A gas-fired humidifier comprising:

• a. an atmospheric pressure storage tank for holding a volume of water, the storage tank having a make-up water inlet and a steam outlet;
• b. a gas-fired burner and combustion blower assembly;
• c. a primary heat exchanger connected to the gas-fired burner and combustion blower assembly, the primary heat exchanger being located within the storage tank and configured to heat the volume of water to generate steam;
• d. wherein the gas-fired humidifier exchanges heat between flue gases, generated by the gas fired burner and combustion blower assembly, and intake air fed to the gas-fired burner and combustion blower assembly and exchanges heat between the flue gases and water delivered to the make-up water inlet to achieve a thermal efficiency of greater than 90 percent and a NOx(3) output of less than 20 parts per million (ppm);
• and
• e. a secondary heat exchanger having a first heat exchange section for heating a first fluid stream and a separate second heat exchange section for heating a second fluid stream, the first and second heat exchange sections being in heat transfer communication with exhaust gases generated by the gas-fired burner and combustion blower assembly, wherein the first fluid stream is a combustion air stream in fluid communication with an inlet of the gas-fired burner and combustion blower assembly.