Skip to content

Chapter 4 — VENTILATION AIR

408.0 Filters.

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.

408.0 Filters. [OSHPD 1, 1R, 2, 3, 4 & 5]408.1 General. Filter efficiencies shall be certified by the manufacturer and shall be based on ASHRAE 52.2 Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size when specifically set forth in these standards.

408.1.1 A filter gauge shall be installed across each fil- ter bank serving central air systems. The gauge shall be red lined or a filter alarm light installed to signal when the recommended maximum static pressure drop has been reached. 408.1.2 Central air-handling systems are defined as any unit requiring duct work on the supply or inlet side that serve more than one room. 408.1.3 Filter banks shall be visually inspected for torn media and bypass in filter frames by means of a flashlight or equivalent, both with fans in operation and stopped. Tears in media and bypass in filter frames shall be elim- inated in accordance with the manufacturer’s directions and the requirements of the enforcing agency prior to commencing operation of the system.

408.1.4 Central air-handling systems shall be main- tained in a reasonably clean condition during construc- tion and shall be cleaned as necessary prior to replacement of temporary filter used during construction to ensure that clean air will be delivered to the occupied spaces. 408.1.5 Filter bank No. 1 shall be located upstream of the air-conditioning equipment. Filter bank No. 2 and filter bank No. 3 shall be located downstream of the sup- ply fan and all cooling and humidification equipment with efficiencies as indicated in Table 4-B or Table 4-C. Exception: Dry steam-type humidifiers for local room humidity control may be installed in the supply air duct downstream of the final filter bank where designs are specifically approved by the enforcing agency. Dry steam is that which is defined in the ASHRAE HVAC Systems and Equipment Handbook. 408.1.6 Filter bank No. 2 and filter bank No. 3 media shall be rigid or supported (noncollapsing type) and shall operate on the principles of impingement, strain- ing, and diffusion.

Get a plain-English answer with a citation back to this text.

Ask AI about this code
Export this section
▸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

GoCodebook provides public access, search, citation, multilingual explanation, and practical interpretation of legally adopted building regulations. It is not a substitute for the official ICC or California code publications.