Establishes minimum regulations for mechanical systems using prescriptive and performance-related provisions. The IMC was developed with broad-based principles that make possible the use of new materials, methods and design.

Important changes in the 2021 IMC® include:

• Clothes dryer exhaust terminals required to be at least 3 feet from any opening into a building.
• Polyurethane spray-applied foam on the exterior of ducts in attics and crawl spaces required to meet specific smoke and flame index limits.
• Fire and smoke dampers must be provided with approved access for inspection and maintenance.
• Refrigerant tables updated to include new refrigerants.
• Addition of condensate termination identification markings and discharge restrictions.
• Approved factory-built combination intake/exhaust terminations permitted, relaxing separation requirement.
• 30% reduction in minimum mechanical ventilation for whole-house balanced ventilation systems.
• Continuous operation requirement for manicure and pedicure station exhaust systems.
• Grease duct horizontal cleanout required within 3 feet of a horizontal discharge fan.