About This Book
The 2025 California Mechanical Code (CMC) is Title 24, Part 4 of the California Code of Regulations. It sets minimum safety, design, and installation standards for HVAC, refrigeration, and related mechanical systems.
Key Details
- Base Standard: Adopts the 2024 Uniform Mechanical Code (UMC) with California-specific amendments.
- Effective Date: January 1, 2026.
- Scope: Covers ventilation, exhaust and duct systems, combustion air, chimneys, vents, boilers, pressure vessels, refrigeration, hydronics, fuel gas piping, and solar/geothermal energy systems.
Major 2025 Updates
- Establishes mandatory, enforceable standards for certified Testing, Adjusting, and Balancing (TAB) and duct leakage testing by approved agencies (e.g., TABB, AABC, NEBB).
- Integrates tighter energy efficiency requirements, low Global Warming Potential (GWP) refrigerant rules, and enhanced indoor air quality (IAQ) mandates.
Practice Tests Using This Book
This book is required or recommended for 1 licensing exam. Our practice tests include questions based on this material.