The 2018 edition of the Uniform Mechanical Code (UMC©) represents the most current approaches in the mechanical field. It is the sixth edition developed under the ANSI Consensus process is designated as an American National Standards by the American National Standards Institute (ANSI). The 2018 edition of the UMC reached a major milestone as it addresses specific provisions for low flammability refrigerants such as A2L and B2L; which makes it one of the first codes in the industry to address specific provisions for these low Global Warming Potential (GWP) refrigerants. 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 2018 UMC include:

• New clearance requirements for solid-fuel burning appliances, ducts serving Type I hood exhaust system, and product conveying ducts (Chapter 3)
• New provisions for Type I and Type II exhaust systems and product conveying ducts.
• New sizing provisions for duct systems, duct leakage testing requirements, installations and closure requirements for flexible air ducts, and new provisions for air dispersions systems (Chapter 6)
• New requirements for pressure regulators and electric furnaces (Chapter 9)
• New refrigerant system requirements, such as A2L and B2L low flammability refrigerants; machinery room requirements such as access, openings, detectors, and ventilation systems; and new pressure limiting-device provisions for compressors (Chapter 11)
• New pressure testing requirements for piping and components, expansion tanks, and materials for hydronic systems (Chapter 12)
• New requirements for piping material, overpressure protection and gas piping installation for fuel gas piping systems (Chapter 13)