Description
2021 International Mechanical Code (IMC)
The 2021 International Mechanical Code sets minimum regulations for mechanical systems, using prescriptive and performance related provisions. Published by the International Code Council, it covers HVAC, exhaust systems, boilers, water heaters and refrigeration, and is used by mechanical contractors, engineers and inspectors.
This edition updates the rules for refrigerants, dryer exhaust, ventilation intakes and commercial kitchens. The changes below reflect a shift toward lower global warming potential refrigerants and tighter fire and air quality controls.
A2L refrigerants and refrigerant piping
The 2021 code adds new definitions and safety standards for Group A2L refrigerants, updating machinery room standards to accommodate these lower flammability, lower GWP options. It also adds new requirements for the identification and protection of refrigerant piping.
Dryer exhaust, ventilation and kitchens
Domestic clothes dryer exhaust provisions are updated, with new listings for booster fans under UL 705 and new termination limits. The code clarifies separation distances between outdoor air intakes and contaminant sources such as exhaust outlets, revises clearances for Type I commercial kitchen hoods, and updates grease duct testing protocols.
What is new in this edition
- New definitions and safety standards for Group A2L refrigerants, acknowledging the shift toward lower GWP options.
- Updated provisions for domestic dryer exhaust, including new listings for booster fans under UL 705 and termination limits.
- Clarified separation distances between outdoor air intakes and contaminant sources like exhaust outlets.
- New requirements for the identification and protection of refrigerant piping.
- Revised clearances for Type I commercial kitchen hoods and updated grease duct testing protocols.
- Adjusted requirements for smoke control systems in large volume spaces such as atriums.
Book details
- Title: 2021 International Mechanical Code (IMC)
- Publisher: International Code Council
- Edition: 2021
- ISBN-13: 9781609839642
Questions buyers ask
Who uses the 2021 International Mechanical Code?
Mechanical contractors, engineers and inspectors use it to design and check HVAC, exhaust, boiler, water heater and refrigeration systems.
What changed in the 2021 edition?
It adds A2L refrigerant standards, updates dryer exhaust and booster fan rules, clarifies ventilation intake separation distances, and revises commercial kitchen hood clearances, among other changes.
Does this edition cover A2L refrigerants?
Yes. It adds new definitions and safety standards for Group A2L refrigerants and updates machinery room standards to accommodate them.
What changed for clothes dryer exhaust?
Booster fans now need a UL 705 listing, and the code sets new termination limits for domestic dryer exhaust.
Does the code address commercial kitchen hoods?
Yes. Clearances for Type I hoods are revised and grease duct testing protocols are updated.
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