2021 International Mechanical Code – ICC IMC-2021

Scope:
The 2021 IMC® establishes minimum requirements for the design, installation, maintenance, and inspection of mechanical systems in all types of buildings. It covers HVAC systems, ventilation, exhaust systems, ductwork, boilers, hydronics, combustion air, chimneys, refrigeration, and solar thermal installations. It is coordinated with the full suite of 2021 I-Codes and intended for enforcement by jurisdictions adopting model mechanical standards.

Key Features and Provisions in the 2021 IMC:

• General Requirements:
  Updates to appliance access, installation clearances, condensate disposal, and temperature control provisions.
• Ventilation Standards:
  Includes comprehensive mechanical and natural ventilation requirements for occupiable and unoccupied spaces, with special conditions for healthcare and high-hazard environments.
• Exhaust Systems:
  Covers exhaust systems for kitchens, clothes dryers, laboratories, garages, and hazardous materials, including grease ducting and smoke control.
• Duct Systems:
  Regulates duct construction, fire and smoke damper installations, insulation, air filters, and smoke control interfaces.
• Combustion Air & Chimneys:
  Directs users to NFPA and IFGC standards for combustion air. Covers chimneys, vents, and flue systems for solid and liquid fuel appliances.
• Specific Appliances & Equipment:
  Installation standards for fireplaces, unit heaters, dryers, sauna heaters, commercial cooking appliances, and fuel cell power systems.
• Boilers & Pressure Vessels:
  Provides safety and installation requirements for boilers, water heaters, expansion tanks, and safety relief devices.
• Refrigeration Systems:
  Sets classification, design, piping, testing, and maintenance standards for mechanical refrigeration.
• Hydronic Systems:
  Covers hot/chilled water piping, valves, insulation, antifreeze, and embedded systems.
• Fuel Oil & Solar Thermal:
  Includes safety requirements for oil piping, tanks, and solar space/water heating systems.
• Appendices:
  Contains permit fee schedules, chimney pass-through diagrams, and board of appeals procedures.

The 2021 edition reflects updates from the ICC’s consensus code development process and integrates current ASHRAE, NFPA, and ANSI standards for industry-aligned implementation.