The 2015 edition of the Uniform Mechanical Code (UMC©) represents the most current approaches in the mechanical field. It is the fifth edition developed under the ANSI Consensus process is designated as an American National Standards by the American National Standards Institute (ANSI). Contributions to the content of this code were made by every segment of the built industry, including such diverse interests as consumers, enforcing authorities, installers/maintainers, labor, manufacturers, research/standards/ testing laboratories, special experts and users. The UMC provides complete requirements for the installation and maintenance of heating, ventilating, cooling and refrigeration systems, while at the same time allowing latitude for innovations and new technologies. Key changes to the 2012 UMC include: New general requirements for condensate wastes and control, installation of appliances on sloped roofs, and clearances to combustible constructions (Chapter 3) New ventilation provisions, such as the classification of recirculated and transferred air, parking garages exhaust, and natural ventilation (Chapter 4) New exhaust provisions for clothes dryers, Type I hoods and grease ducts, dishwashing machines, and downdraft appliances (Chapter 5) New duct systems requirements for factory-made air ducts, plastic ducts, and for ducts used in underground installations (Chapter 6) New appliances provisions, such as electric duct heaters, electric ranges, refrigeration appliances, and ductless mini-split systems (Chapter 9) New refrigeration system requirements, such as the refrigeration concentration limit, ventilation for refrigeration machinery rooms, pressure vessels, and pressure relief valve discharge (Chapter 11) New hydronic systems provisions (Chapter 12)