CMC · California Mechanical Code
What work does the California Mechanical Code apply to?
The CMC applies whenever you install, alter, repair, move, replace, add to, use, or maintain mechanical systems (HVAC, ventilation, refrigeration, exhaust, etc.). Most such jobs require a mechanical permit (see exemptions in § 104.2), must follow code requirements in § 101.2 and related sections, and are subject to inspection and testing by the Authority Having Jurisdiction.
Last reviewed: July 6, 2026
What the code requires — plain English
The California Mechanical Code (CMC) applies to the erection, installation, alteration, repair, relocation, replacement, addition to, use, or maintenance of mechanical systems within the jurisdiction — in short, almost any work on mechanical systems unless explicitly exempted. See § 101.2 for the scope of application.
The CMC governs the work you do on mechanical systems (HVAC, ventilation, refrigeration, exhaust, incinerators, etc.): if you install, alter, move, replace, maintain, or repair it, the CMC usually applies. See § 101.2.
Requirements in detail
Basic scope (what “mechanical systems” covers)
- Mechanical systems include equipment, appliances, fixtures, fittings and appurtenances such as ventilating, heating, cooling, air‑conditioning and refrigeration systems, incinerators and other energy‑related systems. See the cross-reference in the Building Code and the CMC scope. § 101.2 and Building Code § 101.4.2.
Permit requirements and exempt work
- A mechanical permit is required to make an installation, alteration, repair, replacement, or remodel of a mechanical system regulated by the code, except where an exemption applies. See § 104.1.
- Common exemptions (work that generally does not require a permit) include portable heating appliances, portable ventilating equipment, portable cooling units, portable evaporative coolers, closed systems of steam/hot/chilled water piping within equipment, certain replacement parts that do not alter approval, refrigeration equipment that is part of equipment already permitted, and unit refrigerating systems. See § 104.2.
Conflicts, existing installations, and maintenance
- Where this mechanical code conflicts with the California Plumbing Code, the Plumbing Code prevails. Where manufacturer instructions, standards, or the code conflict, the more stringent requirement controls. See § 102.1.
- Existing mechanical systems lawfully in place when the code was adopted may continue to be used, maintained, or repaired in accordance with their original design provided they do not create a hazard. See § 102.2.
- Owners (or their agents) are responsible to keep mechanical systems, materials, and appurtenances maintained in operating condition; devices and safeguards required by the code must be maintained. See § 102.3.
Inspections, tests, and approvals
- Tests and inspections required by the CMC must be performed in the presence of the Authority Having Jurisdiction; approval is issued when tests confirm compliance. See § 105.3 and § 105.3.3.
- No connection to a fuel or energy source may be made for equipment requiring a permit until approved by the Authority Having Jurisdiction (temporary connections for testing are permitted). See § 105.4.
Quick decision table
| Decision question | Typical values / outcome | Code Reference |
|---|---|---|
| Does the work involve a mechanical system (HVAC, ventilation, refrigeration, exhaust, incinerator, etc.)? | Yes → CMC applies | § 101.2 |
| Is the work an installation, alteration, repair, relocation, replacement, addition, use, or maintenance? | Yes → CMC applies | § 101.2 |
| Is a permit required? | Generally yes for installations/alterations/repairs/replacements; see exemptions | § 104.1 |
| Work exempt from permit? | Portable appliances/units; closed steam/hot/chilled water piping within regulated equipment; replacement parts that do not alter approval; unit refrigerating systems, etc. | § 104.2 |
| Conflict with Plumbing Code? | Plumbing Code controls | § 102.1 |
| Can existing lawful installations remain? | Yes, if original design/location remains and no hazard results | § 102.2 |
| Testing/approval requirement? | Tests performed in presence of Authority Having Jurisdiction; approval issued when compliant | § 105.3 / § 105.3.3 |
Exceptions & special cases
- Exemptions listed in § 104.2 are limited and specific; being “portable” or “a closed system within regulated equipment” is key to exemption. Do not assume small size alone makes a system exempt — check the listed items. § 104.2.
- Where other codes apply (for example, energy or health‑care ventilation rules), those requirements may supersede or add to CMC requirements (see building-code cross‑references). See § 101.4 (references) and the CMC provisions on ventilation and healthcare spaces.
- The Authority Having Jurisdiction may waive submission of construction documents for simple jobs or allow partial permits for phased work, at its discretion. See § 104.3.1 and related permit validity/extension rules.
Common mistakes
- Assuming all small or “minor” mechanical changes are permit‑exempt — the CMC limits exemptions to specific items in § 104.2; most HVAC replacements require a permit.
- Confusing which code controls: for gas piping or appliance connections, the Plumbing Code or other referenced codes may control certain elements (see § 102.1 and CBC cross‑references).
- Failing to obtain inspections or to test equipment in the presence of the Authority Having Jurisdiction; approval is required before final connection/operation in many cases. See § 105.3 and § 105.4.
- Overlooking maintenance obligations: owners are responsible to keep mechanical systems in operating condition per § 102.3.
Worked example — replacing a central air conditioner
Scenario: You (homeowner) plan to replace a 4‑ton packaged air conditioner and extend ductwork to add one new supply register.
- Does the CMC apply? Yes — replacement and installation of HVAC equipment and ductwork are actions listed in the scope: erection, installation, alteration, replacement. See § 101.2.
- Is a permit required? Yes — mechanical permits are required for installation, alteration, repair, replacement or remodel of a mechanical system unless an exemption applies. This project is not a portable appliance or the other exemptions, so § 104.1 requires a permit.
- Inspections and testing: The installation will require the prescribed inspections/tests and approval by the Authority Having Jurisdiction before final service connections are made, per § 105.3 and § 105.4.
- Timing: If you obtain a permit, be aware the permit can expire if work does not commence or is abandoned per the permit expiration rules (see permit validity/expiration provisions). See § 104.4.3.
Conclusion: Obtain a mechanical permit, submit required construction documents or plans as required by the Authority Having Jurisdiction, schedule required inspections, and follow the manufacturer’s instructions and the CMC requirements. See § 104.1, § 104.3.1, § 105.3.
Related provisions (CMC sections you’ll likely consult)
- § 101.1 — Title (Uniform Mechanical Code).
- § 101.2 — Scope (primary controlling section for what work the CMC applies to).
- § 102.1 — Conflicts between codes (plumbing vs mechanical, manufacturer instructions, more stringent rule prevails).
- § 102.2 — Existing installations (continued use/repair where lawful).
- § 102.3 — Maintenance responsibilities.
- § 104.1 — Permits required for mechanical work.
- § 104.2 — Exempt work not requiring a permit (limited list).
- § 104.3.1 — Construction documents requirements for permits.
- § 105.3 — Testing of systems and inspections.
- § 105.4 — Connection to service utilities; approval before connection.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 104.0 High relevance — show source text
104.0 Permits.
104.1 Permits Required. It shall be unlawful for a person, firm, or corporation to make an installation, alteration, repair, replacement, or remodel a mechanical system regulated by this code except as permitted in Section 104.2, or to cause the same to be done without first obtaining a separate mechanical permit for each separate building or structure.
104.2 Exempt Work. A permit shall not be required for the following:
(1) A portable heating appliance, portable ventilating equipment, a portable cooling unit, or a portable evaporative cooler.
(2) A closed system of steam, hot, or chilled water piping within heating or cooling equipment regulated by this code.
(3) Replacement of a component part that does not alter its original approval and is in accordance with other applicable requirements of this code.
(4) Refrigerating equipment that is part of the equipment for which a permit has been issued pursuant to the requirements of this code.
(5) A unit refrigerating system.
Exemption from the permit requirements of this code shall not be deemed to grant authorization for work to be done in violation of the provisions of the code or other laws or ordinances of this jurisdiction.
104.3 Application for Permit. To obtain a permit, the applicant shall first file an application therefore in writing on a form furnished by the Authority Having Jurisdiction for that purpose. Such application shall:
(1) Identify and describe the work to be covered by the permit for which application is made.
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(2) Describe the land upon which the proposed work is to be done by legal description, street address, or similar description that will readily identify and definitely locate the proposed building or work.
(3) Indicate the use or occupancy for which the proposed work is intended.
(4) Be accompanied by construction documents and other data in accordance with Section 104.3.1.
(5) Be signed by the permittee or the permittee’s authorized agent. The Authority Having Jurisdiction shall be permitted to require evidence to indicate such authority.
(6) Give such other data and information in accordance with the Authority Having Jurisdiction.
104.3.1 Construction Documents. Construction documents, engineering calculations, diagrams, and other data shall be submitted in two or more sets, or in a digital format where permitted by the Authority Having Jurisdiction, with each application for a permit. The construction documents, computations, and specifications shall be prepared by, and the mechanical system designed by, a registered design professional. Construction documents shall be drawn to scale with clarity to identify that the intended work to be performed is in accordance with the code.
Exception: The Authority Having Jurisdiction shall be permitted to waive the submission of construction documents, calculations, or other data where the Authority Having Jurisdiction finds that the nature of the work applied for is such that reviewing of construction documents is not necessary to obtain compliance with the code.
104.3.2 Plan Review Fees. Where a plan or other data is required to be submitted in accordance with Section 104.3.1, a plan review fee shall be paid at the time of submitting construction documents for review.
The plan review fees for mechanical system work shall be determined and adopted by this jurisdiction.
CMC § 101.1 High relevance — show source text
PART 1—SCOPE AND APPLICATION
SECTION 101—SCOPE AND GENERAL REQUIREMENTS
[A] 101.1 Title. These regulations shall be known as the Building Code of [ NAME OF JURISDICTION ], hereinafter referred to as “this code.”
[A] 101.2 Scope. The provisions of this code shall apply to the construction, alteration, relocation, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures.
Exception: Detached one- and two-family dwellings and townhouses not more than three stories above grade plane in height with a separate means of egress, and their accessory structures not more than three stories above grade plane in height, shall comply with this code or the California Residential Code .
[A] 101.2.1 Appendices. Provisions in the appendices shall not apply unless specifically adopted.
[A] 101.3 Purpose. The purpose of this code is to establish the minimum requirements to provide a reasonable level of safety, health and general welfare through structural strength, means of egress, stability, sanitation, light and ventilation, energy conservation, and for providing a reasonable level of life safety and property protection from the hazards of fire, explosion or dangerous conditions, and to provide a reasonable level of safety to firefighters and emergency responders during emergency operations.
[A] 101.4 Referenced codes. The other codes specified in Sections 101.4.1 through 101.4.7 and referenced elsewhere in this code shall be considered to be part of the requirements of this code to the prescribed extent of each such reference.
[A] 101.4.1 Gas. The provisions of the California Plumbing Code and/or the California Mechanical Code shall apply to the installation of gas piping from the point of delivery, gas appliances and related accessories as covered in this code. These requirements apply to gas piping systems extending from the point of delivery to the inlet connections of appliances and the installation and operation of residential and commercial gas appliances and related accessories.
[A] 101.4.2 Mechanical. The provisions of the California Mechanical Code shall apply to the installation, alterations, repairs and replacement of mechanical systems, including equipment, appliances, fixtures, fittings and appurtenances, including ventilating, heating, cooling, air-conditioning and refrigeration systems, incinerators and other energy-related systems.
[A] 101.4.3 Plumbing. The provisions of the California Plumbing Code shall apply to the installation, alteration, repair and replacement of plumbing systems, including equipment, appliances, fixtures, fittings and appurtenances, and where connected to a water or sewage system and all aspects of a medical gas system. The provisions of the California Plumbing Code shall apply to private sewage disposal systems.
[A] 101.4.4 Property maintenance. The provisions of the California Existing Building Code shall apply to existing structures and premises; equipment and facilities; light, ventilation, space heating, sanitation, life and fire safety hazards; responsibilities of owners, operators and occupants; and occupancy of existing premises and structures.
CMC § 1.11.5.1 High relevance — show source text
1.11.5.1 Existing Group I-1 or R Occupancies. Licensed 24-hour care in a Group I-1 or R occupancy in existence and originally classified under previously adopted state codes shall be reinspected under the appropriate previous code, provided there is no change in the use or character which would place the facility in a different occupancy
group.
1.11.6 Certificate of Occupancy. A Certificate of Occupancy shall be issued as specified in Title 24, Part 2, California Building Code, Section 111.
Exception: Certificates of occupancy are not required for work exempt from permits in accordance with Section 105.2 of the California Building Code.
1.11.7 Temporary Structures and Uses. See Title 24, Part 2, California Building Code, Section 108.
1.11.8 Service Utilities. See Title 24, Part 2, California Building Code, Section 112.
1.11.9 Stop Work Order. See Title 24, Part 2, California Building Code, Section 115.
1.11.10 Unsafe Buildings, Structures, and Equipment. See Title 24, Part 2, California Building Code, Section 116.
1.11.11 Adopting Agency Identification. The provisions of this code applicable to buildings identified in this Section 1.11.0 will be identified in the Matrix Adoption Tables under the acronym SFM.
1.12.0 Reserved for the State Librarian.
1.13.0 Reserved for the Department of Water Resources.
1.14.0 Reserved for the State Lands Commission.
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DIVISION II
SCOPE AND ADMINISTRATION
101.0 General.
101.1 Title. This document shall be known as the “Uniform Mechanical Code,” may be cited as such, and will be referred to herein as “this code.”
101.2 Scope. The provisions of this code shall apply to the erection, installation, alteration, repair, relocation, replacement, addition to, use, or maintenance of mechanical systems within this jurisdiction.
101.3 Purpose. This code is an ordinance providing minimum requirements and standards for the protection of the public health, safety, and welfare.
101.4 Unconstitutional. Where a section, subsection, sentence, clause, or phrase of this code is, for a reason, held to be unconstitutional, such decision shall not affect the validity of the remaining portions of this code. The legislative body hereby declares that it would have passed this code, and each section, subsection, sentence, clause, or phrase thereof, irrespective of the fact that one or more sections, subsections, sentences, clauses, and phrases are declared unconstitutional.
CMC § 105.3.1 High relevance — show source text
No test or inspection shall be required where a mechanical system, or part thereof, is set up for exhibition purposes and has no connection with water or an energy fuel supply. In cases where it would be impractical to provide the required water or air tests, or for minor installations and repairs, the Authority Having Jurisdiction shall be permitted to make such inspection as deemed advisable in order to be assured that the work has been performed in accordance with the intent of this code. Joints and connections in the mechanical system shall be airtight, gastight, or watertight for the pressures required by the test.
105.3.1 Defective Systems. In buildings or premises condemned by the Authority Having Jurisdiction because of an insanitary condition of the mechanical system, or part thereof, the alterations in such system shall be in accordance with the requirements of this code.
105.3.2 Retesting. Where the Authority Having Jurisdiction finds that the work will not pass the test, necessary corrections shall be made, and the work shall be resubmitted for test or inspection.
105.3.3 Approval. Where prescribed tests and inspections indicate that the work is in accordance with this code, a certificate of approval shall be issued by the Authority Having Jurisdiction to the permittee on demand.
105.4 Connection to Service Utilities. No person shall make connections from a source of energy or fuel to a mechanical system or equipment regulated by this code and for which a permit is required until approved by the Authority Having Jurisdiction. The Authority Having Jurisdiction shall be permitted to authorize temporary connection of the mechanical system equipment to the source of energy or fuel for the purpose of testing the equipment.
106.0 Violations and Penalties.
106.1 General. It shall be unlawful for a person, firm, or corporation to erect, construct, enlarge, alter, repair, move, improve, remove, convert, demolish, equip, use, or maintain a mechanical system or permit the same to be done in violation of this code.
106.2 Notices of Correction or Violation. Notices of correction or violation shall be written by the Authority Having Jurisdiction and shall be permitted to be posted at the site of the work or mailed or delivered to the permittee or their authorized representative.
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DIVISION II SCOPE AND ADMINISTRATION
Refusal, failure, or neglect to comply with such notice or order within 10 days of receipt thereof, shall be considered a violation of this code and shall be subject to the penalties set forth by the governing laws of the jurisdiction.
106.3 Penalties. A person, firm, or corporation violating a provision of this code shall be deemed guilty of a misdemeanor, and upon conviction thereof, shall be punishable by a fine, imprisonment, or both set forth by the governing laws of the jurisdiction. Each separate day or a portion thereof, during which a violation of this code occurs or continues, shall be deemed to constitute a separate offense.
106.4 Stop Orders. Where work is being done contrary to the provisions of this code, the Authority Having Jurisdiction shall be permitted to order the work stopped by notice in writing served on persons engaged in the doing or causing such work to be done, and such persons shall forthwith stop work until authorized by the Authority Having Jurisdiction to proceed with the work.
CMC § 1.1.2 High relevance — show source text
1.1.2 Purpose. The purpose of this code is to establish the minimum requirements to safeguard the public health, safety and general welfare through structural strength, means of egress facilities, stability, access to persons with disabilities, sanitation, adequate lighting and ventilation and energy conservation; safety to life and property from fire and other hazards attributed to the built environment; and to provide safety to firefighters and emergency responders during emergency operations.
1.1.3 Scope. The provisions of this code shall apply to the construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures throughout the State of California. [HCD 1 & 2] The provisions of this code shall apply to repair, alteration, change of occupancy, addition to and relocation of every existing building or structure or any appurtenances connected or attached to such buildings or structures throughout the State of California.
1.1.3.1 Nonstate-regulated buildings, structures and applications. Except as modified by local ordinance pursuant to Section 1.1.8, the following standards in the California Code of Regulations, Title 24, Parts 2, 2.5, 3, 4, 5, 6, 7, 9, 10 and 11 shall apply to all occupancies and applications not regulated by a state agency.
1.1.3.2 State-regulated buildings, structures and applications. The model code, state amendments to the model code and/or state amendments where there are no relevant model code provisions shall apply to the following buildings, structures and applications regulated by state agencies as specified in Sections 1.2 through 1.14, except where modified by local ordinance pursuant to Section 1.1.8. When adopted by a state agency, the provisions of this code shall be enforced by the appropriate enforcing agency, but only to the extent of authority granted to such agency by the state legislature.
Note: See “How to Distinguish Between Model Code Language and California Amendments” in the front of the code. 1. State-owned buildings, including buildings constructed by the Trustees of the California State University, and to the extent permitted by California laws, buildings designed and constructed by the Regents of the University of California, and regulated by the Building Standards Commission. See Section 1.2 for additional scope provisions. 2. Section 1.3 is reserved for the Board of State Community Corrections. 3. Section 1.4 is reserved for the Department of Consumer Affairs. 4. Section 1.5 is reserved for the California Energy Commission. 5. Section 1.6 is reserved for the Department of Food and Agriculture. 6. Section 1.7 is reserved for the Department of Public Health. 7. Hotels, motels, lodging houses, apartments, dwellings, dormitories, condominiums, shelters for homeless persons, congregate residences, employee housing, factory-built housing and other types of dwellings containing sleeping _accommodations with or without common toilets or cooking facilities.
CMC § 1.12.0 High relevance — show source text
1.12.0 Reserved for the State Librarian.
1.13.0 Reserved for the Department of Water Resources.
1.14.0 Reserved for the State Lands Commission.
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DIVISION II
SCOPE AND ADMINISTRATION
101.0 General.
101.1 Title. This document shall be known as the “Uniform Mechanical Code,” may be cited as such, and will be referred to herein as “this code.”
101.2 Scope. The provisions of this code shall apply to the erection, installation, alteration, repair, relocation, replacement, addition to, use, or maintenance of mechanical systems within this jurisdiction.
101.3 Purpose. This code is an ordinance providing minimum requirements and standards for the protection of the public health, safety, and welfare.
101.4 Unconstitutional. Where a section, subsection, sentence, clause, or phrase of this code is, for a reason, held to be unconstitutional, such decision shall not affect the validity of the remaining portions of this code. The legislative body hereby declares that it would have passed this code, and each section, subsection, sentence, clause, or phrase thereof, irrespective of the fact that one or more sections, subsections, sentences, clauses, and phrases are declared unconstitutional.
101.5 Validity. Where a provision of this code, or the application thereof to a person or circumstance, is held invalid, the remainder of the code, or the application of such provision to other persons or circumstances, shall not be affected thereby.
102.0 Applicability. 102.1 Conflicts Between Codes. Where the requirements within the jurisdiction of this mechanical code conflict with the requirements of the plumbing code, the plumbing code shall prevail. In instances where this code, applicable standards, or the manufacturer’s installation instructions conflict, the more stringent provisions shall prevail. Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall prevail. [OSHPD 1, 1R, 2, 3, 4 & 5] See Chapter 1, Division I, Section 1.1.7
102.2 Existing Installations. Mechanical systems lawfully in existence at the time of the adoption of this code shall be permitted to have their use, maintenance, or repair continued where the use, maintenance, or repair is in accordance with the original design and location and no hazard to life, health, or property has been created by such mechanical system.
102.3 Maintenance. Mechanical systems, materials, and appurtenances, both existing and new, of a premise under the Authority Having Jurisdiction shall be maintained in operating condition. Devices or safeguards required by this code shall be maintained in accordance with the code edition under
which installed.
The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a mechanical system to be reinspected.
**102.3.1 Commercial HVAC Systems.
CMC § 104.4.2 High relevance — show source text
The Authority Having Jurisdiction shall be permitted to issue a permit for the construction of a part of a mechanical system before the entire construction documents for the whole system have been submitted or approved, provided adequate information and detailed statements have been filed in accordance with pertinent requirements of this code. The holder of such permit shall be permitted to proceed at the holder’s risk without assurance that the permit for the entire building, structure, or mechanical system will be granted.
104.4.2 Validity of Permit. The issuance of a permit or approval of construction documents shall not be construed to be a permit for, or an approval of, a violation of the provisions of this code or other ordinance of the jurisdiction. No permit presuming to give authority to violate or cancel the provisions of this code shall be valid.
The issuance of a permit based upon plans, specifications, or other data shall not prevent the Authority Having Jurisdiction from thereafter requiring the correction of errors in said plans, specifications, and other data or from preventing building operations being carried on thereunder where in violation of this code or of other ordinances of this jurisdiction. 104.4.3 Expiration. A permit issued by the Authority Having Jurisdiction under the provisions of this code shall expire by limitation and become null and void where the work authorized by such permit is not commenced within 180 days from the date of such permit, or where the work authorized by such permit is suspended or abandoned at a time after the work is commenced for a period of 180 days. Before such work is recommenced, a new permit shall first be obtained to do so, and the fee, therefore, shall be one-half the amount required for a new permit for such work, provided no changes have been
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made or will be made in the original construction documents for such work, and provided further that such suspension or abandonment has not exceeded 1 year. 104.4.3.1 Expiration. [BSC] On or after January 1, 2019, every permit issued shall become invalid unless the work on the site authorized by such per- mit is commenced within 12 months after its issuance or if the work authorized on the site by such permit is suspended or abandoned for a period of 12 months after the time the work is commenced. The building official is authorized to grant, in writ- ing, one or more extensions of time, for periods not more than 180 days each. The extension shall be requested in writing and justifiable cause demon- strated. (See Health and Safety Code Section 18938.5 and 18938.6). 104.4.4 Extension. A permittee holding an unexpired permit shall be permitted to apply for an extension of the time within which work shall be permitted to commence under that permit where the permittee is unable to commence work within the time required by this section. The Authority Having Jurisdiction shall be permitted to extend the time for action by the permittee for a period not exceeding 180 days upon written request by the permittee showing that circumstances beyond the control of the permittee have prevented action from being taken. No permit shall be extended more than once. In order to renew action on a permit after expiration, the permittee shall pay a new full permit fee. **104.4.5 Suspension or Revocation.
CMC § 401.2 High relevance — show source text
401.2 Indoor Swimming Pools. The design of ventilation systems serving an indoor aquatic facility (natatorium) shall comply with the Uniform Swimming Pool, Spa and Hot Tub Code (USPSHTC).
401.3 Filters. [BSC-CG & DSA-SS] In mechanically ven- tilated buildings, provide regularly occupied areas of the building with air filtration media for outside and return air that provides at least a Minimum Efficiency Reporting Value (MERV) of 13. MERV 13 filters shall be installed prior to occupancy, and recommendations for maintenance with fil- ters of the same value shall be included in the operation and maintenance manual in compliance with Chapter 5, Division 5.5 of the California Green Building Standards Code (CAL- Green).
Exception: Existing mechanical equipment.
401.3.1 Labeling. Installed filters shall be clearly labeled by the manufacturer indicating the MERV rating.
402.0 Ventilation Air.
402.1 Occupiable Spaces. Occupiable spaces listed in Table 402.1 shall be designed to have ventilation (outdoor) air for occupants in accordance with this chapter. [DSA-SS] Ven- tilation air requirements for occupancies regulated by the California Energy Commission are found in the California Energy Code.
[CEC] Ventilation air requirements for occupancies regu- lated by the California Energy Commission and found in the California Energy Code supersede those of the California Mechanical Code.
[OSHPD 1, 2, 3, 4 & 5] Health care spaces shall meet the ventilation requirements found in Table 4-A. Ventilation rates for areas not specified in Table 4-A shall have minimum ven- tilation and air change rates per ANSI/ASHRAE Standard 62.1. Where areas with prescribed ventilation rates in both Standards 62.1 and Table 4-A exist, the higher of the two air change rates shall be used.
402.1.1 Construction Documents. The outdoor air ventilation rate and air distribution assumptions made in the design of the ventilation system shall be clearly identified on the construction documents.
402.1.2 Ventilation in Health Care Facilities.
Mechanical ventilation for health care facilities shall be designed and installed in accordance with this code, ASHRAE/ASHE 170, and NFPA 99. [OSHPD 1, 1R, 2, 3, 4 & 5] Ventilation for health care facilities shall be designed and installed in accordance with this code and Table 4-A. All supply-air, return air, and exhaust-air sys- tems shall comply with this code and ASHRAE 170. When the requirements of this code conflict with ASHRAE 170, the most restrictive requirements shall prevail. The text of ASHRAE 170 shall be modified as follows:
(1) ASHRAE 170. Section 6.1.2.1 -- Also see Section 319.0.
(2) ASHRAE 170. Section 6.3.1.3 – Modify as follows: Relief air other than class 1 shall discharge at least 10 feet (3048 mm) from any outside air intake.
CMC § 105.2.5 High relevance — show source text
105.2.5 Responsibility. It shall be the duty of the holder of a permit to make sure that the work will stand the test prescribed before giving the notification.
The equipment, material, and labor necessary for inspection or tests shall be furnished by the person to whom the permit is issued or by whom inspection is requested.
105.2.6 Reinspections. A reinspection fee shall be permitted to be assessed for each inspection or reinspection where such portion of work for which inspection is called is not complete or where required corrections have not been made.
This provision shall not be interpreted as requiring reinspection fees the first time a job is rejected for failure to be in accordance with the requirements of this code, but as controlling the practice of calling for inspections before the job is ready for inspection or reinspection.
Reinspection fees shall be permitted to be assessed where the approved plans are not readily available to the inspector, for failure to provide access on the date for which the inspection is requested, or for deviating from plans requiring the approval of the Authority Having Jurisdiction.
To obtain reinspection, the applicant shall file an application therefore in writing upon a form furnished
for that purpose and pay the reinspection fee in accordance with Table 104.5.
In instances where reinspection fees have been assessed, no additional inspection of the work will be performed until the required fees have been paid. 105.3 Testing of Systems. Mechanical systems shall be tested and approved in accordance with this code or the Authority Having Jurisdiction. Tests shall be conducted in the presence of the Authority Having Jurisdiction or the Authority Having Jurisdiction’s duly appointed representative.
No test or inspection shall be required where a mechanical system, or part thereof, is set up for exhibition purposes and has no connection with water or an energy fuel supply. In cases where it would be impractical to provide the required water or air tests, or for minor installations and repairs, the Authority Having Jurisdiction shall be permitted to make such inspection as deemed advisable in order to be assured that the work has been performed in accordance with the intent of this code. Joints and connections in the mechanical system shall be airtight, gastight, or watertight for the pressures required by the test.
105.3.1 Defective Systems. In buildings or premises condemned by the Authority Having Jurisdiction because of an insanitary condition of the mechanical system, or part thereof, the alterations in such system shall be in accordance with the requirements of this code.
105.3.2 Retesting. Where the Authority Having Jurisdiction finds that the work will not pass the test, necessary corrections shall be made, and the work shall be resubmitted for test or inspection.
105.3.3 Approval. Where prescribed tests and inspections indicate that the work is in accordance with this code, a certificate of approval shall be issued by the Authority Having Jurisdiction to the permittee on demand.
105.4 Connection to Service Utilities. No person shall make connections from a source of energy or fuel to a mechanical system or equipment regulated by this code and for which a permit is required until approved by the Authority Having Jurisdiction. The Authority Having Jurisdiction shall be permitted to authorize temporary connection of the mechanical system equipment to the source of energy or fuel for the purpose of testing the equipment.
106.0 Violations and Penalties.
CMC § 402.1 High relevance — show source text
Table 4-B Filter Efficiencies for Central
Ventilation and Air-Conditioning Systems In General Acute Care Hospitals, Outpatient Facilities,
Licensed Clinics and Acute
Psychiatric Hospitals . . . . . . . . . . . 91
Table 4-C Filter Efficiencies for Central
Ventilation and Air-Conditioning Systems In Skilled Nursing Facilities, Intermediate Care
Facilities and Correctional
Treatment Centers . . . . . . . . . . . . . 91
Table 402.1 Minimum Ventilation Rates in
Breathing Zone . . . . . . . . . . . . . . . . 92
Table 403.2.2 Zone Air Distribution Effectiveness. . 95
Table 403.7 Minimum Exhaust Rates. . . . . . . . . 96
CHAPTER 5 EXHAUST SYSTEMS . . . . . . . . . . 97
501.0 General. . . . . . . . . . . . . . . . . . . . . . 99
501.1 Applicability. . . . . . . . . . . . . . . . . . . 99
502.0 Termination. . . . . . . . . . . . . . . . . . . 99
502.1 Exhaust Opening Protection. . . . . . 99
502.2 Termination of Exhaust Ducts . . . . 99
2025 CALIFORNIA MECHANICAL CODE
Part I Environmental Air Ducts and
Product-Conveying Systems . . . . 99
503.0 Motors, Fans, and Filters . . . . . . . . 99
503.1 General. . . . . . . . . . . . . . . . . . . . . . 99
503.2 Fans . . . . . . . . . . . . . . . . . . . . . . . . 99
504.0 Environmental Air Ducts . . . . . . . . . 99
504.1 General. . . . . . . . . . . . . . . . . . . . . . 99
504.2 Independent Exhaust Systems. . . 100
504.3 Domestic Cooking Exhaust Equipment . . . . . . . . . . . . . . . . . . 100
504.4 Clothes Dryers . . . . . . . . . . . . . . . 100
504.5 Heat Recovery Ventilation (HRV) and Energy Recovery Ventilation (ERV) Systems . . . . . . 101
505.0 Product-Conveying Systems . . . . 101
505.1 General. . . . . . . . . . . . . . . . . . . . . 101
505.2 Incompatible Materials . . . . . . . . . 102
505.3 Flammability Limit. . . . . . . . . . . . . 102
505.4 Air-Moving Devices. . . . . . . . . . . . 102
505.5 Generating Flames, Sparks, or Hot Materials . . . . . . . . . . . . . . 102
505.6 Fire Dampers . . . . . . . . . . . . . . . . 102
505.7 Fire Detection, Smoke Control and Alarm Systems . . . . . . . . . . . . 102
CMC § 1.1.3.2 High relevance — show source text
1.1.3.2 State-Regulated Buildings, Structures, and Applications. The model code, state amendments to the model code, and/or state amendments where there are no relevant model code provisions shall apply to the following buildings, structures, and applications regu- lated by state agencies as specified in Sections 1.2.0 through 1.14.0, except where modified by local ordinance pursuant to Section 1.1.8. When adopted by a state agency, the provisions of this code shall be enforced by the appropriate enforcing agency, but only to the extent of authority granted to such agency by the state legislature.
Note: See “How to Distinguish Between Model Code Language and California Amendments” in the front of the code.
(1) State-owned buildings, including buildings constructed by the Trustees of the California State University, and to the extent permitted by California laws, buildings designed and constructed by the
Regents of the University of California, and regu- lated by the Building Standards Commission. See Section 1.2.0 for additional scope provisions.
(2) Section 1.3.0 is reserved for the Board of State and Community Corrections.
(3) Section 1.4.0 is reserved for the Department of Consumer Affairs.
(4) Section 1.5.0 is reserved for the California Energy Commission.
(5) Section 1.6.0 is reserved for the Department of Food and Agriculture.
(6) Organized camps, laboratory animal quarters, public swimming pools, radiation protection, commissaries serving mobile food preparation vehi- cles, and wild animal quarantine facilities regulated by the Department of Public Health. See Section 1.7.0 for additional scope provisions.
(7) Hotels, motels, lodging houses, apartments, dwellings, dormitories, condominiums, shelters for homeless persons, congregate residences, employee housing, factory-built housing and other types of dwellings containing sleeping accommodations with or without common toilets or cooking facilities. See Section 1.8.2.1.1 for additional scope provisions.
(8) Accommodations for persons with disabilities in buildings containing newly constructed covered multifamily dwellings, new common use areas serving existing covered multifamily dwellings, additions to existing buildings where the addition alone meets the definition of covered multifamily dwellings and new common-use areas serving new covered multifamily dwellings which are regulated by the Department of Housing and Community Development. See Section 1.8.2.1.2 for additional scope provisions.
(9) Permanent buildings and permanent accessory build- ings or structures constructed within mobilehome parks and special occupancy parks regulated by the Department of Housing and Community Development. See Section 1.8.2.1.3 for additional scope provisions.
(10)Accommodations for persons with disabilities regu- lated by the Division of the State Architect. See Section 1.9.1 for additional scope provisions.
(11) Public elementary and secondary schools, commu- nity college buildings and state-owned or state- leased essential service buildings regulated by the Division of the State Architect. See Section 1.9.2 for additional scope provisions.
(12)Reserved for the State Historical Building Safety Board with the Division of the State Architect.
CMC § 4.54 High relevance — show source text
Electrical:
Repairs and maintenance: Minor repair work, including the replacement of lamps or the connection of approved portable electrical equipment to approved permanently installed receptacles.
Radio and television transmitting stations: The provisions of this code shall not apply to electrical equipment used for radio and television transmissions, but do apply to equipment and wiring for power supply, the installations of towers and antennas.
Temporary testing systems: A permit shall not be required for the installation of any temporary system required for the testing or servicing of electrical equipment or apparatus.
Gas:
- Portable heating appliance.
- Replacement of any minor part that does not alter approval of equipment or make such equipment unsafe.
Mechanical:
- Portable heating appliance.
- Portable ventilation equipment.
- Portable cooling unit.
- Steam, hot or chilled water piping within any heating or cooling equipment regulated by this code.
- Replacement of any part that does not alter its approval or make it unsafe.
- Portable evaporative cooler.
- Self-contained refrigeration system containing 10 pounds (4.54 kg) or less of refrigerant and actuated by motors of 1 horsepower (746 W) or less.
Plumbing:
The stopping of leaks in drains, water, soil, waste or vent pipe; provided, however, that if any concealed trap, drainpipe, water, soil, waste or vent pipe becomes defective and it becomes necessary to remove and replace the same with new material, such work shall be considered as new work, and a permit shall be obtained and inspection made as provided in this code.
The clearing of stoppages or the repairing of leaks in pipes, valves or fixtures, and the removal and reinstallation of water closets, provided that such repairs do not involve or require the replacement or rearrangement of valves, pipes or fixtures.
[A] 105.2.1 Emergency repairs. Where equipment replacements and repairs must be performed in an emergency situation, the permit application shall be submitted within the next working business day to the code official.
2025 CALIFORNIA EXISTING BUILDING CODE 1-25
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ADMINISTRATION
[A] 105.2.2 Repairs. Application or notice to the code official is not required for repairs to structures and items listed in Section 105.2 provided that such repairs do not include any of the following:
- The cutting away of any wall, partition or portion thereof.
- The removal or cutting of any structural beam or load-bearing support.
- The removal or change of any required means of egress or rearrangement of parts of a structure affecting the egress requirements.
- Any addition to, alteration of, replacement or relocation of any standpipe, water supply, sewer, drainage, drain leader, gas, soil, waste, vent or similar piping, or electric wiring.
- Mechanical or other work affecting public health or general safety.
[A] 105.2.3 Public service agencies. A permit shall not be required for the installation, alteration or repair of generation, transmission, distribution or metering, or other related equipment that is under the ownership and control of public service agencies by established right.
[A] 105.3 Application for permit. To obtain a permit, the applicant shall first file an application therefor in writing on a form furnished by the Department of Building Safety for that purpose. Such application shall:
- Identify and describe the work in accordance with Chapter 3 to be covered by the permit for which application is made.
Frequently asked questions
Do I always need a permit to replace an HVAC unit?
Generally yes — replacement of HVAC equipment that alters, replaces, or installs regulated mechanical systems requires a permit under § 104.1, unless the work fits a narrow exemption list in § 104.2 (for example, certain portable units or closed internal piping).
What is the single most important section to check for applicability?
Check § 101.2 first — it states the code applies to erection, installation, alteration, repair, relocation, replacement, addition to, use, or maintenance of mechanical systems.
If my job is “minor,” can I skip plans and inspections?
Not necessarily. The Authority Having Jurisdiction may waive document submission in limited cases, but inspections and required tests under § 105.3 still apply unless specifically exempted in § 104.2. Always confirm with the local permitting office.
What happens if another code conflicts with the CMC?
Where a conflict exists with the Plumbing Code or other referenced codes, the provisions of that code may prevail; in conflicts among code, standards, or manufacturer instructions the more stringent requirement controls. See § 102.1.
Who is responsible for maintaining mechanical systems?
The owner or the owner’s designated agent is responsible to maintain mechanical systems and required safeguards in operating condition, per § 102.3.
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