CMC · California Mechanical Code
System types & applicability
This hub explains what systems the CMC covers, why determining applicability matters, and points readers to the primary chapters and sections to check.
Last reviewed: July 6, 2026
Overview
This part of the California Mechanical Code (CMC) defines which mechanical systems the code regulates — heating, ventilation, air‑conditioning, refrigeration, fuel‑gas and process piping, ducts and plenums, chimneys/vents, geothermal loops, and the installation of specific appliances — and sets the basic scope and limits for those provisions (see §301.1 for the general coverage).
Knowing which system chapter applies is essential for safe, compliant design and for resolving overlapping rules: the code establishes chapter‑level scopes (for example, duct systems in Chapter 6, §601.1), combustion‑air rules (Chapter 7, §701.1), appliance installation (Chapter 9, §901.1), and fuel‑gas piping scope (Chapter 13, §1301.1), among others.
The CMC also tells users how to handle conflicts between codes and standards (the more‑stringent provision or the plumbing code where noted) and addresses applicability to existing installations and required maintenance — provisions that affect whether a new rule applies to repairs, alterations, or continued operation. See §102.1 and related sections for those principles.
In this section
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 4.0 High relevance — show source text
EQUIPMENT TYPE SUBCATEGORY OR CONDITION MINIMUM EFFICIENCY TEST PROCEDURE Air cooled
(dehumidification mode)– 4.0_ISMRE_ AHRI 920 Air source heat pumps
(dehumidification mode)– 4.0_ISMRE_ AHRI 920 Water cooled
(dehumidification mode)Cooling tower condenser water 4.9_ISMRE_ AHRI 920 Water cooled
(dehumidification mode)Chilled Water 6.0_ISMRE_ 6.0_ISMRE_ Air source heat pump
(heating mode)– 2.7_ISCOP_ AHRI 920 Water source heat pump
(dehumidification mode)Ground source, closed loop 4.8_ISMRE_ AHRI 920 Water source heat pump
(dehumidification mode)Ground-water source 5.0_ISMRE_ 5.0_ISMRE_ Water source heat pump
(dehumidification mode)Water source 4.0_ISMRE_ 4.0_ISMRE_ Water source heat pump
(heating mode)Ground source, closed loop 2.0_ISCOP_ AHRI 920 Water source heat pump
(heating mode)Ground-water source 3.2_ISCOP_ 3.2_ISCOP_ Water source heat pump
(heating mode)Water source 3.5_ISCOP_ 3.5_ISCOP_ TABLE E 503.7.1(14) ELECTRICALLY OPERATED DX-DOAS UNITS, SINGLE-PACKAGE AND REMOTE CONDENSER, WITH ENERGY RECOVERY—MINIMUM EFFICIENCY REQUIREMENTS
[ASHRAE 90.1: TABLE 6.8.1-14]
TABLE E 503.7.1(13) ELECTRICALLY OPERATED DX-DOAS UNITS, SINGLE-PACKAGE AND REMOTE CONDENSER, WITHOUT ENERGY RECOVERY—MINIMUM EFFICIENCY REQUIREMENTS
[ASHRAE 90.1: TABLE 6.8.1-13]
EQUIPMENT TYPE SUBCATEGORY OR RATING CONDITION MINIMUM EFFICIENCY TEST PROCEDURE Air cooled
(dehumidification mode)– 5.2_ISMRE_ AHRI 920 Air source heat pumps
(dehumidification mode)– 5.2_ISMRE_ AHRI 920 Water cooled
(dehumidification mode)Cooling tower condenser water 5.3_ISMRE_ AHRI 920 Water cooled
(dehumidification mode)Chilled Water 6.6_ISMRE_ 6.6_ISMRE_ Air source heat pump
(heating mode)– 3.3_ISCOP_ AHRI 920 Water source heat pump
(dehumidification mode)Ground source, closed loop 5.2_ISMRE_ AHRI 920 Water source heat pump
(dehumidification mode)Ground-water source 5.8_ISMRE_ 5.8_ISMRE_ Water source heat pump
(dehumidification mode)Water source 4.8_ISMRE_ 4.8_ISMRE_ Water source heat pump
(heating mode)Ground source, closed loop 3. CMC § 120.4 High relevance — show source text
Nonresidential and hotel/motel buildings shall comply with the applicable requirements of Sections 120.4(a) through 120.4(g).
Exception to Section 120.4: Systems serving healthcare facilities shall comply with the applicable requirements of the California Mechanical Code.
(a) CMC compliance. All air distribution system ducts and plenums, including but not limited to building cavities, mechanical closets, air-handler boxes and support platforms used as ducts or plenums, shall meet the requirements of the CMC Sections 601.0, 602.0, 603.0, 604.0, and 605.0, and ANSI/SMACNA-006-2006 HVAC Duct Construction Standards Metal and Flexible, 3rd Edition incorporated herein by reference. Connections of metal ducts and the inner core of flexible ducts shall be mechanically fastened. Openings shall be sealed with mastic, tape, aerosol sealant or other duct-closure system that meets the applicable requirements of UL 181, UL 181A, or UL 181B. If mastic or tape is used to seal openings greater than [1] / 4 inch, the combination of mastic and either mesh or tape shall be used.
Portions of supply-air and return-air ducts conveying heated or cooled air located in one or more of the following spaces shall be insulated to a minimum installed level of R-8:
Outdoors; or
In a space between the roof and an insulated ceiling; or
In a space directly under a roof with fixed vents or openings to the outside or unconditioned spaces; or
In an unconditioned crawlspace; or
In other unconditioned spaces.
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NONRESIDENTIAL, HOTEL/MOTEL OCCUPANCIES, AND COVERED PROCESSES—MANDATORY REQUIREMENTS
Portions of supply-air ducts that are not in one of these spaces, including ducts buried in concrete slab, shall be insulated to a minimum installed level of R-4.2 or be enclosed in directly conditioned space.
(b) Duct and plenum materials.
- Factory-fabricated duct systems. A. All factory-fabricated duct systems shall comply with UL 181 for ducts and closure systems, including collars, connections and splices, and be labeled as complying with UL 181. UL 181 testing may be performed by UL laboratories or a laboratory approved by the Executive Director. B. All pressure-sensitive tapes, heat-activated tapes, and mastics used in the manufacture of rigid fiberglass ducts shall comply with UL 181 and UL 181A. C. All pressure-sensitive tapes and mastics used with flexible ducts shall comply with UL 181 and UL 181B. D. All ductwork and plenums with pressure class ratings shall be constructed to Seal Class A. Joints and seams of duct systems and their components shall not be sealed with cloth-back rubber adhesive duct tapes unless such tape is used in combination with mastic and drawbands.
Exception to Section 120.4(b)1D: Ductwork located in occupied space and exposed to view is not required to meet Seal Class A.
CMC § 608.0 High relevance — show source text
(3) Heating and cooling equipment in accordance with ACCA Manual S or other equivalent methods.
E 608.0 Low VOC Solvent Cement and Primer.
E 608.1 General. Primers and solvent cements used to join plastic pipe, and fittings shall be in accordance with Section E 608.1.1 and Section E 608.1.2.
E 608.1.1 Solvent Cement. Solvent cement, including one-step solvent cement, shall have a volatile organic compound (VOC) content of less than or equal to 65 ounces per gallon (oz/gal) (487 g/L) for CPVC cement, 68 oz/gal (509 g/L) for PVC cement, and 43 oz/gal (322 g/L) for ABS cement, as determined by the South Coast Air Quality Management District’s Laboratory Methods of Analysis for Enforcement Samples, Method 316A. E 608.1.2 Primer. Primer shall have a volatile organic compound (VOC) content of less than or equal to 73 oz/gal (546 g/L), as determined by the South Coast Air Quality Management District’s Laboratory Methods of Analysis for Enforcement Samples, Method 316A.
E 701.0 Installer Qualifications.
E 701.1 Scope. The provisions of this section address minimum qualifications of installers of mechanical systems covered within the scope of this appendix.
E 702.0 Qualifications.
E 702.1 General. Where permits are required, the Authority Having Jurisdiction shall have the authority to require contractors, installers, or service technicians to demonstrate competency. Where determined by the Authority Having Jurisdiction, the contractor, installer, or service technician shall be licensed to perform such work.
Part I
E 801.0 Heating, Ventilation, and Air Conditioning Systems Commissioning. E 801.1 Applicability. The provisions of this section apply to the commissioning of commercial and institutional HVAC systems.
E 802.0 Commissioning. E 802.1 Commissioning Requirements. HVAC commissioning shall be included in the design and construction processes of the project to verify that the HVAC systems and components meet the owner’s project requirements and in accordance with this appendix. Commissioning shall be performed in accordance with this appendix by personnel trained and certified in commissioning by a nationally recognized organization. Commissioning requirements shall include the following:
(1) Owner’s project requirements
(2) Basis of design
(3) Commissioning measures shown in the construction doc uments
(4) Commissioning plan
(5) Functional performance
(6) Testing
(7) Post construction documentation and training
(8) Commissioning report
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APPENDIX E
HVAC systems and components covered by this appendix as well as process equipment and controls, and renewable energy systems shall be included in the scope of the commissioning requirements. E 802.2 Owner’s Project Requirements (OPR). The performance goals and requirements of the HVAC system shall be documented before the design phase of the project begins. This documentation shall include not less than the following:
(1) Environmental and sustainability goals
(2) Energy efficiency goals
(3) Indoor environmental quality requirements
(4) Equipment and systems performance goals
CMC § 911.0 High relevance — show source text
2||||||||||X|X|X||X|X|||||||||| |911.0||||||||||||||||||X||||||| |911.2||||||||||X|X|X||X|X|||||||||| |912.3(1)||||X|X|||||||||||||||||||| |915.3.1||||X|X|||||||||||||||||||| |915.3.1.1||||X|X|||||||||||||||||||| |929.0||||†|†|||||||||||||||||||| |929.1||||†|†||||||||||||||||||||
This state agency does not adopt sections identified with the following symbol: 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.
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CHAPTER 9
INSTALLATION OF SPECIFIC APPLIANCES
901.0 General.
901.1 Applicability. This chapter addresses requirements for the design, construction, and installation of specific appliances. In addition to the requirements of this chapter, appliances shall comply with the general requirements of Chapter 3.
902.0 General.
902.1 Nonindustrial Appliances. This chapter is applicable primarily to nonindustrial-type appliances and installations and, unless specifically indicated, does not apply to industrial-type appliances and installations. Listed appliances shall be installed in accordance with their listing and the manufacturer’s installation instructions or, as elsewhere specified in this chapter, as applicable to the appliance. Unlisted appliances shall be installed as specified in this part as applicable to the appliances.
902.2 Combustion Air from Bedroom or Bathroom. Appliances shall not be installed so their combustion, ventilation, and dilution air are obtained only from a bedroom or bathroom unless the bedroom or bathroom has the required volume in accordance with Section 701.4. [NFPA 54:10.1.2]
[OSHPD 1, 1R, 2, 4 & 5] Warm air furnaces shall not be installed under openable windows on exterior walls. 902.3 Added or Converted Appliances. When additional or replacement appliances or equipment is installed or an appliance is converted to gas from another fuel, the location in which the appliances or equipment is to be operated shall be checked to verify the following:
(1) Air for combustion and ventilation is provided where required, in accordance with the provisions of Section 701.0. Where existing facilities are not adequate, they shall be upgraded to meet Section 701.0 specifications.
(2) The installation components and appliances meet the clearances to combustible material provisions of Section 303.10. It shall be determined that the installation and operation of the additional or replacement appliances do not render the remaining appliances unsafe for continued operation.
(3) The venting system is constructed and sized in accordance with the provisions of Section 802.0.
CMC § 519.0 Medium relevance — show source text
519.0 Type II Hood Exhaust System Requirements . . . . . . . . . . . . . . . . 132
519.1 Where Required . . . . . . . . . . . . . . 132
519.2 Construction of Type II Hoods . . . 132
519.3 Type II Hood Exhaust System Net Airflow . . . . . . . . . . . . . . . . . . 132
519.4 Type II Exhaust Duct Systems . . . 132
519.5 Termination of Type II Hood Exhaust System . . . . . . . . . . . . . . 132
519.6 Makeup Air . . . . . . . . . . . . . . . . . . 133
519.7 Independent Exhaust Duct System . . . . . . . . . . . . . . . . . 133
CHAPTER 6 DUCT SYSTEMS . . . . . . . . . . . . . 135
601.0 General. . . . . . . . . . . . . . . . . . . . . 137
601.1 Applicability. . . . . . . . . . . . . . . . . . 137
601.2 Sizing Requirements . . . . . . . . . . 137
602.0 Material. . . . . . . . . . . . . . . . . . . . . 137
602.1 General. . . . . . . . . . . . . . . . . . . . . 137
602.2 Combustibles Within Ducts or
Plenums . . . . . . . . . . . . . . . . . . . . 137
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602.3 Tall Wood (Mass Timber) Buildings . . . . . . . . . . . . . . . . . . . . 137
602.4 Metallic . . . . . . . . . . . . . . . . . . . . . 138
602.5 Nonmetallic Ducts. . . . . . . . . . . . . 138
602.6 Vibration Isolators. . . . . . . . . . . . . 138
602.7 Corridors. . . . . . . . . . . . . . . . . . . . 138
603.0 Installation of Ducts . . . . . . . . . . . 138
603.1 General. . . . . . . . . . . . . . . . . . . . . 138
603.2 Under-Floor or Crawl Space. . . . . 138
603.3 Metal Ducts. . . . . . . . . . . . . . . . . . 138
603.4 Flexible Air Ducts . . . . . . . . . . . . . 138
603.5 Plastic Ducts. . . . . . . . . . . . . . . . . 139
603.6 Protection of Ducts . . . . . . . . . . . . 139
603.7 Support of Ducts. . . . . . . . . . . . . . 139
603.8 Protection Against Flood Damage . 139
603.9 Joints and Seams of Ducts. . . . . . 139
Table 603.9.1 Closure Markings . . . . . . . . . . . . . 140
CMC § 1.11.0. Medium relevance — show source text
Adopting Agency BSC BSC-
CGSFM HCD Col6 Col7 DSA Col9 Col10 OSHPD Col12 Col13 Col14 Col15 Col16 Col17 BSCC DPH AGR DWR CEC CA SL SLC Adopting Agency BSC BSC-
CGSFM 1 2 1-AC AC ** SS** ** SS/CC** 1 1R 2 3 4 5 6 6 6 6 6 6 6 6 6 Adopt Entire Chapter X X X X X X X X X X X X X Adopt Entire Chapter as
amended (amended sections
listed below)Adopt only those sections
that are listed belowChapter/Section This state agency does not adopt sections identified with the following symbol: 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.
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CHAPTER 7
COMBUSTION AIR
701.0 General.
701.1 Applicability. Air for combustion, ventilation, and dilution of flue gases for appliances installed in buildings shall be obtained by application of one of the methods covered in Section 701.4 through Section 701.9.3. Where the requirements of Section 701.4 are not met, outdoor air shall be introduced in accordance with methods covered in Section
701.6 through Section 701.9.3.
Exceptions:
(1) This provision shall not apply to direct vent appliances.
(2) Type 1 clothes dryers that are provided with makeup air in accordance with Section 504.4.1. [NFPA 54:9.3.1.1]
701.1.1 Other Types of Appliances. Appliances of other than natural draft design, appliances not designated as Category I vented appliances, and appliances equipped with power burners shall be provided with combustion, ventilation, and dilution air in accordance with the appliance manufacturer’s instructions. [NFPA 54:9.3.1.2]
CMC § 1.11.0. Medium relevance — show source text
5_||||||||||X|X|X||X|X|||||||||| |321.0||||||||||X||X|X|X|X|||||||||| |322.0
||||||||||X||X|X|X|X|||||||||| |323.0
||||||||||X|X|X||X|X|||||||||| |324.0||||||||||X|X|X|X|X|X|||||||||| |325.0||||||||||||X|||||||||||||This state agency does not adopt sections identified with the following symbol: 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.
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CHAPTER 3
GENERAL REGULATIONS
301.0 General.
301.1 Applicability. This chapter covers general requirements for heating, ventilating, air-conditioning, refrigeration, miscellaneous heat-producing, and energy-utilizing equipment or appliances. Such equipment or appliances shall comply with the requirements of this code.
301.2 Approval. Equipment or appliance shall be approved by the Authority Having Jurisdiction for safe use or comply with applicable nationally recognized standards as evidenced by the listing and label of an approved agency. A list of accepted standards is included in Chapter 18. Defective materials or parts shall be replaced in such a manner as not to invalidate an approval.
301.3 Design of Equipment. The installer or contractor shall furnish satisfactory evidence that the appliance is constructed in accordance with the requirements of this code. The permanently attached label of an approved agency shall be permitted to be accepted as such evidence. 301.4 Electrical Connections. For equipment regulated by this code:
(1) Equipment requiring electrical connections of more than 50 volts shall have a positive means of disconnect adjacent to and in sight from the equipment served.
Exception: Other power disconnect means shall be acceptable where in accordance with the California Elec- trical Code .
(2) A 120 volt receptacle shall be located within 25 feet (7620 mm) of the equipment for service and maintenance purposes. The receptacle outlet shall be on the supply side of the disconnect switch. The receptacle need not be located on the same level as the equipment.
(3) Electrical wiring, controls, and connections to equipment and appliances regulated by this code shall be in accordance with the California Electrical Code . 301.5 Oil-Burning Appliances. The tank, piping, and valves for appliances burning oil shall be installed in accordance with the requirements of NFPA 31.
CMC § 1707.6 Medium relevance — show source text
1707.6 Subsurface Conditions . . . . . . . . . 350
1707.7 Ground-Heat Exchanger Installation Practices. . . . . . . . . . . 350
1707.8 Trenching, Excavation, and Backfill . . . . . . . . . . . . . . . . . . 351
1707.9 Trenches, Tunneling, and Driving . . . . . . . . . . . . . . . . . . 351
1707.10 Excavations and
Open Trenches. . . . . . . . . . . . . . . 351
1707.11 Protection of Piping, Materials, and Structures . . . . . . . 351
1707.12 Sleeves. . . . . . . . . . . . . . . . . . . . . 351
1707.13 Steel Nail Plates . . . . . . . . . . . . . . 351
1707.14 Exterior Piping Protection . . . . . . . 351
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1707.15 Heat Pump and Distribution System Installation . . . . . . . . . . . . 351
1707.16 Pressurizing During Installation . . . . . . . . . . . . . . . . . . 351
1707.17 Horizontal Geothermal
Piping - Materials and Methods . . 351
1707.18 Trenches, Excavation,
and Backfill . . . . . . . . . . . . . . . . . . 351
1708.0 System Start-Up . . . . . . . . . . . . . . 352
1708.1 General. . . . . . . . . . . . . . . . . . . . . 352
1708.2 Operation and Maintenance Manual . . . . . . . . . . . . . . . . . . . . . 352
1708.3 Labeling and Marking . . . . . . . . . . 352
1708.4 Documentation . . . . . . . . . . . . . . . 352
1708.5 Maintenance . . . . . . . . . . . . . . . . . 352
1708.6 Records . . . . . . . . . . . . . . . . . . . . 352
1708.7 System Start-Up . . . . . . . . . . . . . . 352
1708.8 Contaminants . . . . . . . . . . . . . . . . 352
1709.0 Decommissioning and Abandonment . . . . . . . . . . . . . . . . 352
1709.1 General. . . . . . . . . . . . . . . . . . . . . 352
Part II Closed-Loop Systems . . . . . . . . 352
1710.0 General. . . . . . . . . . . . . . . . . . . . . 352
1710.1 Applicability. . . . . . . . . . . . . . . . . . 352
1710.2 Piping and Tubing. . . . . . . . . . . . . 352
1710.3 Borehole Piping and Tubing . . . . . 352
CMC § 2025 Medium relevance — show source text
Materials for piping and tubing must meet the working temperature and pressure of the system. In addition, materials must be compatible with the transfer medium to prevent deformation, bursting, or any chemical action between the material and the transfer medium. The allowable joining methods for piping or tubing are provided for application and enforcement purposes.
Chapter 13 Fuel Gas Piping. Chapter 13 regulates gas piping systems in a building, structure or within the property lines of buildings up to 5 psi. Gas piping systems must supply the minimum volume of gas required by each gas appliance to perform their proper operation under working conditions without exceeding the maximum pressure specified by each manufacturer. Because of the hazards associated with fuel gas, it is important to ensure the gas system has been inspected and tested, and that it is safe to turn on the gas supply to the building.
Chapter 14 Process Piping. Chapter 14 regulates process piping that typically is found in refineries. Process piping is considered the piping or tubing portion that transports liquid or gas, which is used directly in research, laboratory, or production process. This chapter may be used with another chapter of the code. For example, refrigeration piping, fuel gas piping, or fuel oil piping may need to comply with this chapter for process piping and the applicable chapter for materials, design, and installation.
Chapter 15 Solar Energy Systems. Chapter 15 refers the user to the Uniform Solar, Hydronics and Geothermal Code (USHGC) for solar energy system requirements. The USHGC contains comprehensive design, installation, and construction requirements for all types of solar thermal systems, such as drainback, thermosiphon, open-loop, and closed-loop systems. The USHGC also addresses installation of solar photovoltaic (PV) systems including array circuit(s), inverter(s), and controller(s) for such systems.
Chapter 16 Stationary Power Plants. This chapter provides minimum requirements for stationary fuel cell power plants. A fuel cell is a device that produces electricity by a chemical reaction. Fuel cells have been used mostly for satellites. However, the costs of fuel cells have decreased to a point where they are now economically attainable. With the increase in electricity costs, fuel cells are being considered as an alternative for producing electricity.
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FORMAT OF THE UNIFORM MECHANICAL CODE
Chapter 17 Geothermal Energy Systems and Ambient Temperature Loops. Chapter 17 regulates the design, installation, construction, and location of geothermal energy systems and ambient temperature loops (ATLs). This chapter provides the minimum safety requirements for various types of geothermal systems, including building systems coupled with a ground-heat exchangers, submerged heat exchangers using water-based fluid as a heat transfer medium, and groundwater (well). For ease of use and clarification on the applicability of geothermal provisions, Chapter 17 is divided into five parts pertaining to general provisions for all types of geothermal systems, closed-loop systems, open-loop systems, direct-exchange (DX) systems, and ambient temperature loops. For district ambient temperature loops, including those utilizing multiple hybrid systems, Part I through Part V are applicable.
In order to properly design a geothermal system, it is important to know the seasonal variation in the soil temperature, as well as the soil’s inherent capability to store and transmit heat, namely its heat capacity and thermal conductivity. In addition, a properly designed heat pump distribution system is essential for the distribution of geothermal energy.
CMC § 303.7 Medium relevance — show source text
2||||||||||†|†|†|†|†|†|||||||||| |303.7|||X|||||||||||||||||||||| |303.7.1||||X|X|||||||||||||||||||| |305.2_Exception_||||X|X|||||||||||||||||||| |306.2
||||||||||X||||||||||||||| |311.5
|||||||||||||||||||||X|||| |316.2||||X|X|||||||||||||||||||| |316.5||||X|X|||||||||||||||||||| |316.9||||X|X|||||||||||||||||||| |318.0||||||||||X|X|X|X|X|X|||||||||| |319.1||||||||||X|X|||X|X|||||||||| |319.2||||||||||||X||X||||||||||| |320.1||||||||||X|X|||X|X|||||||||| |320.2||||||||||||X||X||||||||||| |320.3|||||||||||||X|||||||||||| |320.4||||||||||X||||X||||||||||| |320.5||||||||||X|X|X||X|X|||||||||| |321.0||||||||||X||X|X|X|X|||||||||| |322.0
||||||||||X||X|X|X|X|||||||||| |323.0
||||||||||X|X|X||X|X|||||||||| |324.0||||||||||X|X|X|X|X|X|||||||||| |325.0||||||||||||X|||||||||||||This state agency does not adopt sections identified with the following symbol: 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.
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CHAPTER 3
GENERAL REGULATIONS
301.0 General.
301.1 Applicability. This chapter covers general requirements for heating, ventilating, air-conditioning, refrigeration, miscellaneous heat-producing, and energy-utilizing equipment or appliances. Such equipment or appliances shall comply with the requirements of this code.
CMC § 104.4.6 Medium relevance — show source text
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INDEX
Retention of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.4.6
Review fees . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.3.2
PLENUMS
Applicability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601.1 Closure systems . . . . . . . . . . . . . . . . . . . . . . . . . . 603.9
Combustibles within . . . . . . . . . . . . . . . . . . . . . . . 602.2
Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
Furnace. . . . . . . . . . . . . . . . . . . . . . . . 802.3.5, 903.2.4,
603.13.4, 904.3, 604.1
Heating and cooling system . . . . . . . . 605.1, E 503.3.1
Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516.6.3
Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . E 503.4.7.1.1
Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . E 503.4.7.2.1
Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.1
Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.5
Serving type II hoods . . . . . . . . . . . . . . . . . . . . . 510.1.7 Supply-air. . . . . . . . . . . . . . . . . . . . . 508.3.5, 508.3.5.3,
508.3.5.3.3, 608.0,
E 503.4.7.1.1
Use of under-floor as supply plenum. . . . . . . . . . . 608.0 Where dampers are required . . . . . . . . . . . . . . . . 701.12
PLUMBING CODE
Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.0
POLYETHYLENE (PE) PIPE OR TUBING
Frequently asked questions
Which CMC chapters govern ducts and plenums?
Ducts and plenums are covered primarily in Chapter 6 (see §601.1 and the Chapter 6 scope and installation sections), which sets material, sizing, installation, and plenum applicability requirements.
Does the CMC regulate fuel‑gas piping?
Yes — fuel‑gas piping up to specified pressures is governed by Chapter 13; see §1301.1 for the scope and applicability of gas piping provisions.
What if the CMC conflicts with another code or a manufacturer’s instructions?
When codes or standards conflict, the CMC directs that the more stringent provision controls; where the mechanical code conflicts with the plumbing code, the plumbing code prevails. See §102.1 for conflict‑resolution rules.
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