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Chapter 4 — VENTILATION AIR

California Mechanical Code (Title 24, Part 4) · 2019 edition · updated 2026-09-10 · California

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

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency BSC BSC-
CG		 SFM HCD DSA OSHPD BSCC DPH AGR DWR CEC CA SL SLC
Adopting Agency
 **BSC ** BSC-
CG		 SFM 1 2 1-AC **AC ** SS SS/CC 1 1R 2 3 4 5 5 5 5 5 5 5 5 5
Adopt Entire Chapter

Adopt Entire Chapter as
amended (amended sections
listed below)
 X X **X ** X X X

Adopt only those sections
that are listed below
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Chapter/Section
401.0
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401.1
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**X **		 X
401.2 with exception
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401.2.1
 X X X
402.0
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 **X ** **X ** **X ** **X ** X
402.1
 X X X
X




402.1.3
 **X ** **X ** **X ** **X ** X
402.3
 **X **
 X
402.5
**X **
X
403.0

**X ** **X ** **X ** **X ** **X ** X
403.7.2.1 – 403.7.2.4
 X **X ** X






405.0
 **X **
 **X **
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407.0 and subsections
**X **
**X **
**X **
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X

408.0 and subsections
**X **
**X **
**X **
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**X **
X

409.0 and subsections
**X **
**X **
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**X **
**X **
X

410.0 and subsections
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**X **
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X

411.0 and subsections
**X **
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**X **
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412.0 and subsections
**X **
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X

413.0 and subsections
**X **
**X **
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**X **
**X **
X

414.0 and subsections
**X **
**X **
**X **
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**X **
X

415.0 and subsections
**X **
**X **
**X **
**X **
**X **
X

416.0 - 416.2
**X **
**X **
**X **
**X **
**X **
X

416.3




X
416.4
 **X **
 **X **
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 X
417.0
**X **
**X **
**X **
**X **
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X
418.0 and subsections
**X **
**X **
**X **
**X **
**X **
X

419.0 and subsections
X





Table 4-A
 **X **
 **X **
 **X ** **X **
 **X **
 X

Table 4-B
**X **
X

**X **
X

Table 4-C
 X
X

Table 402.1
 X X X


Table 403.7~~~~Note 11 & 12

**X **
X

The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

2019 CALIFORNIA MECHANICAL CODE 61

62 2019 CALIFORNIA MECHANICAL CODE

CHAPTER 4

VENTILATION AIR

401.0 General. 401.1 Applicability. This chapter contains requirements for

ventilation air supply, exhaust, and makeup air requirements for occupiable spaces within a building. [OSHPD 1, 1R, 2, 3, 4 & 5] See Sections 404.0 through 418.0. [SFM] Air filters shall comply with all requirements of Part 12, Title 24, Chap- ter 12-71, SFM Standard 12-71-1.

402.0 Ventilation Air. [Not permitted for OSHPD 1, 2,

403.0 Ventilation Rates. [Not permitted for OSHPD 1,

1R, 2, 3, 4 & 5]403.1 General. The design outdoor air intake flow rate for a ventilation system shall be determined in accordance with Section 403.2 through Section 403.9.4.

404.0 Multiple-Zone Systems.404.1 General.

This section presents an alternative procedure for calculating the system ventilation efficiency ( Ev ) where values in Table 403.5.2 are not used. The system ventilation efficiency shall equal the lowest zone ventilation efficiency among the ventilation zones served by the air handler in accordance with Equation 404.1. [ASHRAE 62.1:A1.3]

Ev = minimum ( Evz ) (Equation 404.1)

406.0 Reserved.

407.0 Ventilation System Details. [OSHPD 1, 1R, 2, 3, 4

& 5]

410.0 Laboratory Ventilating Systems and Hoods.

412.0 Boiler, Mechanical, and Electrical Rooms.

[OSHPD 1, 1R, 2, 3, 4 & 5]412.1 Boiler, heater and electrical equipment rooms shall be provided with outdoor air so as to maintain combustion rates of equipment and temperatures in the rooms and in adjoining areas as rated in this chapter.

413.0 Odorous Rooms.

413.0 Odorous Rooms. [OSHPD 1, 1R, 2, 3, 4 & 5] 413.1 Rooms in areas where excessive heat or moisture is generated, where objectional odors or dust are present, or where flammable or toxic gases may accumulate, which are used by health facility personnel or patients, shall be pro- vided with exhaust ventilation to change the air a minimum of ten times per hour.

418.0 Design Requirements for Ethylene Oxide (ETO)

419.0 Neonatal Intensive Care Units.

419.0 Neonatal Intensive Care Units. [OSHPD 1]419.1 Formula Preparation Area. Air shall be supplied over the formulation preparation area by group E, nonaspi- rating supply diffusers. Air shall be returned or exhausted by registers located not less than 3 inches (76 mm) nor more than 8 inches (203 mm) above the finished floor in the cleanup area.

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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
  3. Chapter 3 — GENERAL REGULATIONS
  4. ▸Chapter 4 — VENTILATION AIR
    Overview
    1. 401.2 Filters. [BSC-CG], [DSA-SS & DSA-SS/CC] In
    2. 402.1 Occupiable Spaces.3 & 4] Occupiable spaces listed in
    3. 402.2 Natural Ventilation. Natural ventilation systems
    4. 402.3 Mechanical Ventilation. Where natural ventilation is
    5. 402.4 Outdoor Air Intake Protection. Required outdoorair intak…
    6. 402.5 Bathroom Exhaust Fans. [HCD 1 & HCD 2] Each
    7. 403.2 Zone Calculations. Ventilation zone parameters
    8. 403.3 Single-Zone Systems. For ventilation systems
    9. 403.4 One Hundred Percent Outdoor Air Systems. For
    10. 403.5 Multiple-Zone Recirculating Systems. For ventilation sys…
    11. 403.6 Design for Varying Operating Conditions. Ventilation sys…
    12. 403.7 Exhaust Ventilation. Exhaust airflow shall be provided i…
    13. 404.2 Average Outdoor Air Fraction. The average outdoor air fr…
    14. 404.3 Zone Ventilation Efficiency. The zone ventilation
    15. 403.8 Dynamic Reset. The system shall be permitted to
    16. 403.9 Air Classification and Recirculation. Air shall be
    17. 405.0 Evaporative Cooling System for Health CareFacilities. [F…
    18. 407.1 General.407.1.1 All supply-air, return air, and exhaust-…
    19. 407.3 Air Balance.407.3.1 The ventilation systems shall be des…
    20. 407.4 Air Circulation.407.4.1 Design of the ventilation system…
    21. 407.2 Outdoor Air Intakes and Exhaust Outlets.407.2.1 Outdoor …
    22. 407.5 Variable Air Volume.407.5.1 Variable Air Volume Systems …
    23. 408.0 Filters. [OSHPD 1, 1R, 2, 3, 4 & 5]408.1 General. Filter…
    24. 408.2 Filters for Hospitals.408.2.1 All air-ventilation system…
    25. 408.3 Filters for Skilled Nursing Facilities, Intermedi-
    26. 408.4 Filters for Outpatient Facilities.408.4.1 The air ventil…
    27. 409.2 Duct linings and their use shall meet the requirements
    28. 409.3 Insulation of Ducts. Cold air ducts shall be insu-
    29. 409.4 The anchorage and supporting structural elements for
    30. 410.1 Laboratory Ventilating Systems.[OSHPD 1, 1R, 2, 3, 4 & 5…
    31. 410.2 Exhaust Hoods and Safety Cabinets. Hoods and
    32. 410.3 Laboratory Fume Hoods. Laboratory fume hoods
    33. 411.0 Kitchen and Dining Areas. [OSHPD 1, 1R, 2, 3, 4
    34. 412.2 Floor surfaces in occupied spaces above such rooms
    35. 413.2 Kitchen, morgues and laundries located inside a hos-
    36. 414.0 Airborne Infection Isolation Rooms. [OSHPD
    37. 414.2 Air Distribution. The supply outlets and exhaust
    38. 415.0 Protective Environment Rooms. [OSHPD 1, 1R,
    39. 416.0 Alarms – Airborne Infection Isolation Rooms
    40. 416.2 Other acceptable alarm systems will be allowed when
    41. 416.3 [For OSHPD 4] For correctional treatment centers,
    42. 416.4 Prior to acceptance of the rooms, the alarm system
    43. 417.0 Testing and Balancing Airborne Infection Isola-
    44. 418.1 Air Changes. Sterilization Areas. [OSHPD 1, 1R, 2, 3, 4 …
    45. 418.2 Exhaust Requirements.418.2.1 All air from the ETO steril…
    46. 418.3 Ventilation Requirements.418.3.1 Aeration Units. The aer…
    47. 418.4 Gas Valves. Installation of gas line hand valves at the
    48. 418.5 Alarm Systems. An Audible and visual alarm system
    49. 419.2 Treatment Area/Room. Air shall be supplied over
  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 — REFERENCED STANDARDS
  18. Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
  19. Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
  20. Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
  21. Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
  22. Appendix E — SUSTAINABLE PRACTICES
  23. Appendix F — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
  24. Appendix G — EXAMPLE CALCULATION OF OUTDOOR AIR RATE

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