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Earlier editions: 20222019

Chapter 2 — DEFINITIONS

225.0 – W –

California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-10 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

Wall Heater. See Vented Wall Furnace.

Warm Air Furnace. An environmental heating appliance designed or arranged to discharge heated air through any duct or ducts. This definition shall not include a unit heater.

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Unusually Tight Construction. Construction where:

(1) Walls and ceilings exposed to the outdoors have a continuous water vapor retarder with a rating of 1 perm or less with openings gasketed or sealed.

(2) Weatherstripping is on openable windows and doors.

(3) Caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels, and at penetrations for plumbing, electrical, and gas lines and at other openings. Use (Material). The placing in action or making available for service by opening or connecting a container utilized for confinement of material, whether a solid, liquid, or gas.

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▸Contents — California Mechanical Code (Title 24, Part 4)
California Mechanical Code (Title 24, Part 4)
  1. Chapter 1 — GENERAL CODE PROVISIONS
  2. ▸Chapter 2 — DEFINITIONS
    Overview
    1. 201.1 Applicability. For the purpose of this code, the followi…
    2. 202.1 General. The definitions of terms are arranged alphabeti…
    3. 203.0 – A –
    4. 204.0 – B –
    5. 205.0 – C –
    6. 206.0 – D –
    7. 208.0 – F –
    8. 207.0 – E –
    9. 209.0 – G –
    10. 210.0 – H –
    11. 211.0 – I –
    12. 212.0 – J –
    13. 214.0 – L –
    14. 215.0 – M –
    15. 216.0 – N –
    16. 217.0 – O –
    17. 218.0 – P –
    18. 220.0 – R –
    19. 221.0 – S –
    20. 222.0 – T –
    21. 223.0 – U –
    22. 225.0 – W –
    23. 224.0 – V –
    24. 228.0 – Z –
  3. Chapter 3 — GENERAL REGULATIONS
  4. Chapter 4 — VENTILATION AIR
  5. Chapter 5 — EXHAUST SYSTEMS
  6. Chapter 6 — DUCT SYSTEMS
  7. Chapter 7 — COMBUSTION AIR
  8. Chapter 8 — CHIMNEYS AND VENTS
  9. Chapter 9 — INSTALLATION OF SPECIFIC APPLIANCES
  10. Chapter 10 — BOILERS AND PRESSURE VESSELS
  11. Chapter 11 — REFRIGERATION
  12. Chapter 12 — HYDRONICS
  13. Chapter 13 — FUEL GAS PIPING
  14. Chapter 14 — PROCESS PIPING
  15. Chapter 15 — SOLAR ENERGY SYSTEMS
  16. Chapter 16 — STATIONARY POWER PLANTS
  17. Chapter 17 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE…
  18. Chapter 18 — REFERENCED STANDARDS
  19. Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
  20. Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
  21. Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
  22. Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
  23. Appendix E — SUSTAINABLE PRACTICES
  24. Appendix F — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
  25. Appendix G — EXAMPLE CALCULATION OF OUTDOOR AIR RATE
  26. Appendix H — PROFESSIONAL QUALIFICATIONS
  27. Appendix I — INDOOR HORTICULTURAL FACILITIES
  28. Appendix J — CLEAN AIR DELIVERY

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