CMC · California Mechanical Code

When does Chapter 7 (Combustion Air) apply to appliances?

If an appliance needs air for combustion, ventilation, or dilution of flue gases, Chapter 7 applies unless the unit is a direct‑vent appliance or otherwise excluded; use the indoor method (50 ft³ per 1,000 Btu/h) in § 701.4 when the space volume meets the requirement, and if it does not, you must provide outdoor or mechanical/engineered combustion air per § 701.6–§ 701.9.3 — except where § 701.1.1 says follow the manufacturer.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

Chapter 7 applies whenever an appliance installed in a building needs air for combustion, ventilation, or dilution of flue gases; that air must be supplied using one of the methods in § 701.4 through § 701.9.3. If the indoor‑air criteria of § 701.4 cannot be met, the code requires introducing outdoor air using the methods in § 701.6 through § 701.9.3. These applicability rules are set out in § 701.1 (with general scope in § 701.0) and the appliance‑type direction in § 701.1.1.

The single most important rule: use one of the Chapter 7 supply methods (indoors, outdoors, combination, mechanical, or engineered) — and if the indoor method in § 701.4 is not met, you must provide outdoor air per § 701.6–§ 701.9.3.

Requirements in detail

Scope / applicability (who this affects)

Applies to air for combustion, ventilation, and dilution of flue gases for appliances installed in buildings (see § 701.0 and § 701.1).
If the criteria of § 701.4 (indoor combustion air) are not satisfied, the installer must use the outdoor methods in § 701.6–§ 701.9.3.

Built‑in exceptions and alternative paths

Direct vent appliances are explicitly excluded from Chapter 7 applicability.
Type I clothes dryers are excluded if they are provided with makeup air in accordance with § 504.4.1.
Appliances that are not natural‑draft, not Category I, or that have power burners must be provided combustion/ventilation/dilution air in accordance with the appliance manufacturer’s instructions (per § 701.1.1).

Decision table — which rule to follow

Decision dimension	Key values / thresholds	What to do	Code reference
Appliance is a direct‑vent appliance	Any direct‑vent design	Chapter 7 does not apply	§ 701.1
Appliance type	Non‑natural draft, non‑Category I, or power burner	Follow manufacturer’s combustion‑air instructions	§ 701.1.1
You can supply air from inside the building?	Indoor volume meets method in § 701.4	Use indoor combustion‑air method (no outdoor openings needed)	§ 701.1, § 701.4
Indoor method not met	Any	Provide outdoor air per § 701.6–§ 701.9.3 (or combination/mechanical/engineered)	§ 701.1
Minimum indoor volume (standard method)	50 cubic feet per 1,000 Btu/h	Compute required room volume using this factor	§ 701.4.1
Known infiltration rate	< 0.40 ACH or known value	Use the known infiltration method in § 701.4.2	§ 701.4

Key definitions and thresholds (first use is bold)

Direct vent appliance — excluded from Chapter 7 applicability (see § 701.1).
Manufacturer’s instructions — controlling for appliances listed in § 701.1.1 (other than natural‑draft / Category I / power burner appliances).
Minimum volume: 50 ft³ per 1,000 Btu/h — the standard method for indoor combustion air in § 701.4.1.

Exceptions & special cases

Direct‑vent appliances: Chapter 7 does not apply — these appliances draw combustion air from a sealed intake and are regulated by the appliance listing/installation instructions instead. § 701.1 excludes them.
Type I clothes dryers with makeup air: If makeup air is installed per § 504.4.1, the clothes dryer is not covered by Chapter 7’s combustion‑air rules.
Appliances with forced‑draft, power burners, or other non‑natural draft designs: follow the appliance manufacturer’s combustion‑air instructions (manufacturer control supersedes the standard Chapter 7 sizing methods in these cases). § 701.1.1.
Where air infiltration is known and is less than 0.40 ACH, the known‑infiltration method of § 701.4.2 must be used instead of the standard 50 ft³/1,000 Btu/h method.

Common mistakes

Assuming Chapter 7 never applies to appliances inside a mechanical room — it does unless the appliance is a direct‑vent appliance or otherwise excluded. Check § 701.1.
Using the 50 ft³/1,000 Btu/h figure for appliances that are explicitly required to follow the manufacturer’s instructions (non‑Category I / power‑burner appliances). Use § 701.1.1 first.
Forgetting to switch to outdoor‑air methods when indoor volume criteria in § 701.4 can't be met; the code requires outdoor openings or other approved methods in § 701.6–§ 701.9.3.
Treating a Type I clothes dryer as covered by Chapter 7 when makeup air is provided per § 504.4.1; that dryer is an exception.

Worked example — concrete scenario with numbers

Scenario: A gas‑fired natural‑draft furnace (Category I) with input rating 80,000 Btu/h is installed in a room that measures 20 ft × 20 ft × 8 ft (room volume = 3,200 ft³). The appliance is not direct‑vent and has no forced power burner; manufacturer instructions do not override Chapter 7.

Decision steps:

Is Chapter 7 applicable? Yes — the appliance requires combustion/dilution air and is not direct vent; § 701.1 applies.
Can we use the indoor method? Compute the required minimum volume using § 701.4.1 (standard method): 50 ft³ per 1,000 Btu/h. For 80,000 Btu/h → 80 × 50 = 4,000 ft³ required.
Compare to actual room volume: actual = 3,200 ft³ < required 4,000 ft³ → the indoor method is not met.
Code action: because § 701.4 criteria are not met, the installer must provide outdoor air using methods in § 701.6–§ 701.9.3 (for example, outdoor openings sized per the tables/methods in those sections, or mechanical/engineered makeup air). § 701.1 requires this step.

Result: Provide outdoor combustion air (or combination/mechanical/engineered solution) sized per the relevant sections of Chapter 7.

Related provisions

§ 701.0 — General (scope / topic introduction).
§ 701.1 — Applicability (methods, when to use outdoor air; exceptions for direct vent and clothes dryers).
§ 701.1.1 — Other types of appliances; manufacturer’s instructions control for non‑natural draft / non‑Category I / power‑burner appliances.
§ 701.2 — Pressure difference (draft hood/barometric regulator location).
§ 701.3 — Makeup air when exhaust systems interfere with appliances.
§ 701.4, § 701.4.1, § 701.4.2 — Indoor combustion air methods and the 50 ft³/1,000 Btu/h standard and known‑infiltration method.
§ 701.6–§ 701.9.3 — Outdoor, combination, mechanical, and engineered combustion air supply methods (use when § 701.4 is not met).
See Chapter 9 installation rules where appliance location and added/converted appliances require verification that Chapter 7 provisions are met (e.g., § 902.3).

If you want, I can:

produce a one‑page checklist you can print for site use (appliance type → which § to follow → required calculations), or
run another worked example with multiple appliances in the same space (sum inputs, check volume, size openings).

Code references

Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:

CMC § 1.11.0. High relevance — show source text

Adopting Agency	BSC	BSC- CG	SFM	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- CG	SFM	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 below
Chapter/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 § 2025 High relevance — show source text
Systems that carry nonabrasive exhaust, such as smoke, moderate abrasives such as sawdust, and high abrasives such as manganese or acid vapors use product-conveying ducts. Part II provides the minimum fire safety requirements related to the design, installation, inspection, and maintenance of grease-type operations, such as cooking, for both fuel-gas and solid fuel. Cooking produces a significant amount of smoke, fumes, vapors, heat, and other pollutants. Therefore, acceptable kitchen ventilation is necessary to prevent fires from the build-up of grease and to provide the occupants protection from smoke, unpleasant odors, pollutants, and dangerous gases. There are two types of exhaust hoods (Type I and Type II) used in commercial kitchen applications.

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Type I hoods are intended to be installed above equipment or appliances that generate grease or smoke. Type II hoods are intended to be installed above equipment or appliances that generate steam, vapor, heat, or odors and do not generate grease or smoke.

Chapter 6 Duct Systems. Chapter 6 regulates requirements for ducts and plenums that are portions of a heating, cooling, ventilation, or exhaust system. This chapter contains material and installation requirements for metal, gypsum, factory-made, flexible, and plastic ducts. It also contains provisions for duct insulation, dampers, fire protection, and automatic shutoff for the building’s air distribution system. It is worth noting that exhaust ducts are regulated by Chapter 5, and combustion air ducts are regulated by Chapter 7.

Chapter 7 Combustion Air. Chapter 7 regulates combustion air requirements for ventilation and dilution of flue gases for appliances installed in buildings. Fuel-gas appliances not regulated by chapter include direct vent appliances and Type I clothes dryers. Makeup air requirements for Type I clothes dryers are located in Chapter 5. Chapter 7 provides acceptable methods for supplying satisfactory combustion air to ensure proper combustion. Combustion air can be supplied by using indoor combustion air or by introducing the air from the outdoors.

Combustion is the rapid oxidation of fuel to release energy. The oxygen required to release the energy from the fuel normally comes from the air. Incomplete combustion of fuel occurs when inadequate oxygen is provided to the appliance. Combustion is needed to provide ventilation cooling for the casing and internal controls. When a lack of oxygen occurs, some of the carbon is not oxidized, and carbon monoxide forms.

Chapter 8 Chimneys and Vents. Chapter 8 regulates the installation, design, and construction of venting systems for fuel-burning appliances. The provisions addressed within this chapter follow procedures an installer would use to design or evaluate a venting system. Many requirements apply to the design and construction of venting systems, chimneys, installation of gas vents, and the sizing of venting system for a Category I appliance. Sizing venting systems require rigorous engineering calculations. However, the venting sizing requirements and sizing tables in this chapter already perform the calculations for the benefit of the end user.

Combustion appliances produce products of incomplete combustion, including potentially harmful carbon monoxide (CO). It is desirable to vent these products to the outdoors. Although the gas is clean-burning fuel, the products of combustion must not be allowed to collect within a building.
CMC § 701.0 High relevance — show source text
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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]

701.2 Pressure Difference. Where used, a draft hood or a barometric draft regulator shall be installed in the same room or enclosure as the appliance served so as to prevent any difference in pressure between the hood or regulator and the combustion air supply. [NFPA 54:9.3.1.4]

701.3 Makeup Air. Where exhaust fans, clothes dryers, and kitchen ventilation systems interfere with the operation of appliances, makeup air shall be provided. [NFPA 54:9.3.1.5]

701.4 Indoor Combustion Air. The required volume of indoor air shall be determined in accordance with the method

in Section 701.4.1 or Section 701.4.2 except that where the air infiltration rate is known to be less than 0.40 ACH (air change per hour), the method in Section 701.4.2 shall be used. The total required volume shall be the sum of the required volume calculated for appliances located within the space. Rooms communicating directly with the space in which the appliances are installed through openings not furnished with doors, and through combustion air openings sized and located in accordance with Section 701.5, are considered a part of the required volume. [NFPA 54:9.3.2]

701.4.1 Standard Method. The minimum required volume shall be 50 cubic feet per 1000 British thermal units per hour (Btu/h) (4.83 m [3] /kW). [NFPA 54:9.3.2.1]

701.4.2 Known Air Infiltration Rate Method. Where

the air infiltration rate of a structure is known, the minimum required volume shall be determined as follows

[NFPA 54:9.3.2.2]:
CMC § 2025 High relevance — show source text
Chapter 7 Combustion Air. Chapter 7 regulates combustion air requirements for ventilation and dilution of flue gases for appliances installed in buildings. Fuel-gas appliances not regulated by chapter include direct vent appliances and Type I clothes dryers. Makeup air requirements for Type I clothes dryers are located in Chapter 5. Chapter 7 provides acceptable methods for supplying satisfactory combustion air to ensure proper combustion. Combustion air can be supplied by using indoor combustion air or by introducing the air from the outdoors.

Combustion is the rapid oxidation of fuel to release energy. The oxygen required to release the energy from the fuel normally comes from the air. Incomplete combustion of fuel occurs when inadequate oxygen is provided to the appliance. Combustion is needed to provide ventilation cooling for the casing and internal controls. When a lack of oxygen occurs, some of the carbon is not oxidized, and carbon monoxide forms.

Chapter 8 Chimneys and Vents. Chapter 8 regulates the installation, design, and construction of venting systems for fuel-burning appliances. The provisions addressed within this chapter follow procedures an installer would use to design or evaluate a venting system. Many requirements apply to the design and construction of venting systems, chimneys, installation of gas vents, and the sizing of venting system for a Category I appliance. Sizing venting systems require rigorous engineering calculations. However, the venting sizing requirements and sizing tables in this chapter already perform the calculations for the benefit of the end user.

Combustion appliances produce products of incomplete combustion, including potentially harmful carbon monoxide (CO). It is desirable to vent these products to the outdoors. Although the gas is clean-burning fuel, the products of combustion must not be allowed to collect within a building.

Chapter 9 Installation of Specific Appliances. Chapter 9 regulates the minimum requirements for the design, construction and installation of specific appliances. The provisions address the minimum requirements for gas-fired appliances, oil-fired appliances, wood-fired appliances, and electric-type appliances. In addition to the requirements of this chapter, appliances are also required to comply with the general requirements of Chapter 3.

Chapter 10 Boilers and Pressure Vessels. Chapter 10 regulates the construction, installation, operation, repair, and alteration of boilers and pressure vessels. The safety provisions within this chapter address controls and limit devices for automatic boilers, methods of determining expansion tank capacities, discharge piping, relief valves, shutoff valves, gas-pressure and combustion regulators, and inspections and tests. Potable water heaters are free from the requirements of Chapter 10 as they are within the scope of the Uniform Plumbing Code (UPC).

Pressure vessels store large amounts of energy and must comply with ASME Boiler and Pressure Vessel Code (BPVC) Section VIII.1. The stored energy must be contained to prevent disastrous failures. Boilers must comply with ASME BPVC Section I, ASME BPVC Section IV, or NFPA 85. Installing a safety relief valve and expansion tank prevents pressures in the tank from exceeding the design threshold.

Chapter 11 Refrigeration. Chapter 11 regulates the design, installation, and construction requirements of refrigeration systems and the installation and construction of cooling towers. Refrigeration is a method used for achieving heat transfer to cool spaces. Refrigerants are the most common medium used to transfer the heat energy from the low-temperature level to the high-temperature level. Table

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CMC § 902.0 High relevance — show source text
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. Where the existing venting system is not adequate, it shall be upgraded to comply with Section 802.0. [NFPA 54:9.1.2] 902.4 Type of Gas(es). The appliance shall be connected to the fuel gas for which it was designed. No attempt shall be made to convert the appliance from the gas specified on the rating plate for use with a different gas without consulting the installation instructions, the serving gas supplier, or the appliance manufacturer for complete instructions. Listed appliances shall not be converted unless permitted by and in accordance with the manufacturer’s installation instructions. [NFPA 54:9.1.3] 902.5 Safety Shutoff Devices for Unlisted LP-Gas Appliances Used Indoors. Unlisted appliances for use

with undiluted LP-Gases and installed indoors, except attended laboratory equipment, shall be equipped with safety shutoff devices of the complete shutoff type. [NFPA 54:9.1.4] 902.6 Fuel Input Rate. The fuel input rate to the appliance shall not be increased or decreased in violation of the approved rating at the altitude where it is being used. 902.7 Use of Air or Oxygen Under Pressure. Where air or oxygen under pressure is used in connection with the gas supply, effective means such as a back pressure regulator and relief valve shall be provided to prevent air or oxygen from passing back into the gas piping. Where oxygen is used, installation shall be in accordance with NFPA 51. [NFPA 54:9.1.5] 902.8 Appliance Support. Appliances and equipment shall be furnished either with load-distributing bases or with a sufficient number of supports to prevent damage to either the building structure or the appliance and the equipment.
CMC § 608.9 High relevance — show source text
608.9 Floor Registers . . . . . . . . . . . . . . . 143

608.10 Exterior Wall and Interior Stud

Partitions. . . . . . . . . . . . . . . . . . . . 143

608.11 Wall Register . . . . . . . . . . . . . . . . 143

608.12 Distance from Combustible . . . . . 143

608.13 Vapor Barrier . . . . . . . . . . . . . . . . 143

608.14 Prohibited . . . . . . . . . . . . . . . . . . . 143

609.0 Automatic Shutoffs . . . . . . . . . . . . 143

609.1 Air-Moving Systems and Smoke Detectors . . . . . . . . . . . . . . . . . . . 143

609.2 Air-Moving Systems and Smoke Detectors in Group I-2 Occupancies . . . . . . . . . . . . . . . . 144

CHAPTER 7 COMBUSTION AIR . . . . . . . . . . . 145

701.0 General. . . . . . . . . . . . . . . . . . . . . 147

701.1 Applicability. . . . . . . . . . . . . . . . . . 147

701.2 Pressure Difference . . . . . . . . . . . 147

701.3 Makeup Air . . . . . . . . . . . . . . . . . . 147

701.4 Indoor Combustion Air . . . . . . . . . 147

701.5 Indoor Opening Size and Location . . . . . . . . . . . . . . . . . . . . 147

701.6 Outdoor Combustion Air . . . . . . . . 147

701.7 Combination Indoor and Outdoor

Combustion Air . . . . . . . . . . . . . . . 148

701.8 Engineered Installations . . . . . . . . 149

701.9 Mechanical Combustion Air

Supply. . . . . . . . . . . . . . . . . . . . . . 149

701.10 Louvers, Grilles, and Screens . . . 149

701.11 Combustion Air Ducts. . . . . . . . . . 150

701.12 Dampers Prohibited . . . . . . . . . . . 150

702.0 Extra Device or Attachment . . . . . 150

702.1 General. . . . . . . . . . . . . . . . . . . . . 150

CHAPTER 8 CHIMNEYS AND VENTS. . . . . . . 151

801.0 General. . . . . . . . . . . . . . . . . . . . . 153

801.1 Applicability. . . . . . . . . . . . . . . . . . 153

801.2 Venting of Gas Appliances . . . . . . 153

801.3 Appliances Fueled by Other Fuels. 153

802.0 Venting of Appliances. . . . . . . . . . 153

xxxiv
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 § 101.2 High relevance — show source text
Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.2

COMBUSTIBLE CONSTRUCTION, CLOSED

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0

COMBUSTIBLE CONSTRUCTION, OPEN

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217.0

COMBUSTIBLE MATERIAL

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0

COMBUSTIBLE MATERIAL, LIMITED

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214.0

COMBUSTION AIR

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0

Duct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701.11, 701.12

General requirements . . . . . . . . . . . . . . . . . . Chapter 7

COMBUSTION AIR FOR

Boilers, low pressure,

installed in closets . . . . . . . . . . . . . . . . . . . . . . . 904.2

Engineered installations. . . . . . . . . . . . . . . . . . . . . 701.8

Fireplaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912.4

Fossil fuel heating equipment. . . . . . . . . . . . . E 502.6.1

Furnaces, central heating . . . . . . . . . . . . . . 904.2, 907.4

COMBUSTION AIR FROM

Bedroom or bathroom. . . . . . . . . . . . . . . . . . . . . . 902.2

Chimneys and vents . . . . . . . . . . . . . . . . . . . 802.5.11.1

Combination, indoor and outdoor. . . . . . . 701.7, F 103.0

Indoors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701.4

Louvers, grilles and screens . . . . . . . . . . . . . . . . 701.10

Mechanical supply . . . . . . . . . . . . . . . . . . . . . . . . . 701.9

Outdoors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701.6

Refrigeration machinery rooms . . . . . . . . . . . . . . 1106.5

COMMERCIAL FOOD

HEAT-PROCESSING EQUIPMENT
CMC § 2025 Medium relevance — show source text
Appendix B Procedures to be Followed to Place Gas Equipment in Operation. Appendix B provides requirements for the procedures that apply after an appliance is installed in place, piped, and connected to its venting system. The requirements include adjusting the burner input, air adjustments, verifying operation of safety shutoffs, automatic ignition, and protective devices, checking draft for vent-connected appliances, and operating instructions.

Appendix C Installation and Testing of Oil (Liquid) Fuel-Fired Equipment. Appendix C governs the installation, testing, or repair of oil or liquid fuel-burning equipment used in buildings or structures and equipment.

Appendix D Fuel Supply: Manufactured/Mobile Home Parks and Recreational Vehicle Parks. The provisions of this appendix apply to the fuel gas piping systems of mobile home and recreational vehicle parks. These provisions also apply to the use, maintenance, and installation for supplying fuel gas for accessory buildings or structures, and building components.

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FORMAT OF THE UNIFORM MECHANICAL CODE

Appendix E Sustainable Practices. This appendix provides a comprehensive set of technically sound provisions that encourage sustainable practices and works toward improving the design and construction of mechanical systems that result in a positive long-term environmental impact. Environmental sustainability is important because it involves natural resources that human beings need for economic or manufactured capital. Their sustainability is defined by their reliance on infinitely available resources that are naturally occurring, constant, and free to access.

Appendix F Sizing of Venting Systems and Outdoor Combustion and Ventilation Opening Design. Appendix F provides added information on the sizing of gas vents. This appendix is useful to the end user for the proper sizing of venting systems. A series of examples are given that show how to use the tables and other requirements of Chapter 8. In addition, Appendix F shows an example of how to determine the required combination of indoor and outdoor combustion air opening sizes for appliances under Chapter 7. The combustion air example also provides a table that contains the required volume of space per the appliance Btu/h input based on the standard method.

Appendix G Example Calculation of Outdoor Air Rate. Appendix G gives an example of how to calculate the required outdoor air rate under Chapter 4.

Appendix H Professional Qualifications. Appendix H provides a baseline of knowledge for installers, inspectors, or employers working with and around systems covered within the scope of this code to maintain health and safety.

Appendix I Indoor Horticultural Facilities. Appendix I addresses indoor spaces using environmental controls for horticultural cultivation and processing of plants for human ingestion, inhalation, and topical application. The appendix includes recommendations pertaining to fire protection and suppression systems, carbon dioxide detection systems, flammable solvents, ventilation and exhaust systems, particulate and odor control, and fumigation.

Appendix J Clean Air Delivery. Appendix J provides criteria for an increased level of protection for occupant health by delivering and monitoring clean air in occupied areas of certain buildings. This appendix addresses Demand Control Ventilation (DCV) for occupancy groups A, B, E, and I and recommends that each occupiable zone have CO 2 sensors which communicate with building mechanical systems to adjust airflow rates and maintain acceptable CO 2 levels. Additionally, this appendix contains provisions for mechanical system controls pertaining to sensor calibration, intervals for collected data, and automatic remediation actions to increase the amount of outdoor
CMC § 803.1.2 Medium relevance — show source text
Table 803.1.2(4) Masonry Chimney. . . . . . . . . . . . . 179

Table 803.1.2(5) Single-Wall Metal Pipe or Type B Asbestos-Cement Vent. . . . . . . . . 181

Table 803.1.2(6) Exterior Masonry Chimney . . . . . . 182

2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

TABLE OF CONTENTS

Table 803.2(1) Type B Double-Wall Vent . . . . . . 183

Table 803.2(2) Type B Double-Wall Vent . . . . . . . 187

Table 803.2(3) Masonry Chimney. . . . . . . . . . . . . 189

Table 803.2(4) Masonry Chimney. . . . . . . . . . . . . 191

Table 803.2(5) Single-Wall Metal Pipe or Type B Asbestos-Cement Vent . . . 193

Table 803.2(6) Exterior Masonry Chimney . . . . . . 193

Table 803.2(7) Exterior Masonry Chimney . . . . . . 194

Table 803.2(8) Exterior Masonry Chimney . . . . . . 195

Table 803.2(9) Exterior Masonry Chimney . . . . . . 196

CHAPTER 9 INSTALLATION OF

SPECIFIC APPLIANCES. . . . . . . 197

901.0 General. . . . . . . . . . . . . . . . . . . . . 199

901.1 Applicability. . . . . . . . . . . . . . . . . . 199

902.0 General. . . . . . . . . . . . . . . . . . . . . 199

902.1 Nonindustrial Appliances . . . . . . . 199

902.2 Combustion Air from Bedroom

or Bathroom . . . . . . . . . . . . . . . . . 199

902.3 Added or Converted Appliances. . 199

902.4 Type of Gas(es) . . . . . . . . . . . . . . 199

902.5 Safety Shutoff Devices for Unlisted LP-Gas Appliances Used Indoors . . . . . . . . . . . . . . . . 199

902.6 Fuel Input Rate . . . . . . . . . . . . . . . 199

902.7 Use of Air or Oxygen Under Pressure . . . . . . . . . . . . . . . . . . . . 199

902.8 Appliance Support . . . . . . . . . . . . 199

902.9 Flammable Vapors . . . . . . . . . . . . 199

902.10 Solid-Fuel-Burning Appliances . . . 199

902.11 Combination of Appliances and Equipment . . . . . . . . . . . . . . . 199

902.12 Protection of Gas Appliances from Fumes or Gases Other

than Products of Combustion . . . . 199

902.13 Process Air . . . . . . . . . . . . . . . . . . 200
California Plumbing Code Medium relevance — show source text
Chapter 1 Administration.

Chapter 1 regulates the application, enforcement, and administration of subsequent requirements of the code. As well as establishing the scope of the code, this chapter is concerned with enforcing the requirements contained in the body of the code. A plumbing code, as with any other code, is intended to be adopted as a legally enforceable document to safeguard health, safety, property, and public welfare. The code cannot be effective without satisfactory provisions for its administration and enforcement. The Authority Having Jurisdiction is to review the proposed and completed work and to decide whether a plumbing system conforms to the code requirements. As a public servant, the Authority Having Jurisdiction enforces the code in an unbiased, proper manner. The design professional is responsible for the design of a safe plumbing system. The contractor is responsible for installing the system in accordance with the plans.

Chapter 2 Definitions.

To maintain consistency and encourage the use of common terminology, Chapter 2 establishes definitions to provide clarity of terms and promote the use of a common language throughout the code. Understanding definitions within the context of their application enables greater collaboration, efficiency, standardization, and interpretation in applying and enforcing terms used throughout the code. Codes are technical documents, and every term can impact the meaning of the code text. Terms not defined have a normally accepted meaning.

Chapter 3 General Regulations.

Chapter 3 regulates the general requirements, not specific to other chapters, for installing plumbing systems. Many regulations are not specific plumbing requirements but relate to the overall plumbing system. This chapter contains safety requirements for installing plumbing and also contains nonplumbing requirements for identifying pipes, pipe fittings, traps, fixtures, materials, and devices used in plumbing systems. Listing method of approval, based on applicable nationally recognized standards, for the safe and proper installation of plumbing systems, is essential to ensure the protection of public health, safety, and welfare. The safety requirements provide protection for piping, material, and structures, with provisions for installation practices, removing stress and strain of the pipe, sleeving, and hanger support. The building’s structural stability is protected by the regulations for cutting and notching of structural members.

Chapter 4 Plumbing Fixtures and Fixture Fittings.

This chapter regulates the minimum number of plumbing fixtures of a specific type and quality for each building. The fixtures must be properly installed to be usable by the individuals occupying the building. The quality and design of every fixture must conform to the applicable referenced standard. Compliance with this chapter will result in a building or structure having acceptable plumbing fixtures for the sanitary, hygienic, cleaning, washing, and food preparation needs of the occupants. In addition to ensuring resilient fixtures, the chapter also takes into consideration gender-neutral facilities and contains provisions for privacy compartments.

Chapter 5 Water Heaters.

Chapter 5 regulates the design, approval, installation, and safety devices of fuel burning and other types of water heaters with the combustion air requirements for ventilation and dilution of flue gases for appliances installed in buildings. This chapter does not apply to direct-vent appliances. In addition, this chapter regulates the design, construction, installation, and maintenance of chimneys, vents, and their connections to fuel-burning appliances. Methods to supply combustion air may be supplied from an indoor air supply, outdoor air supply, a combination of indoor and outdoor air supply, mechanical air supply, or an engineered system. Combustion air provisions are based on the number of openings and the total

CFC § 2025 Medium relevance — show source text

generally by providing oxygen,
cause or contribute to the combustion of other mate-
rial more than air does.
H280, compressed gas would also apply.|

APPENDIX E-16 2025 CALIFORNIA FIRE CODE

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

APPENDIX E—HAZARD CATEGORIES

TABLE E104.2—CFC AND GHS HAZARD DEFINITIONS COMPARISONa—continued	Col2	Col3	Col4
**CFC MATERIAL**	**CFC CLASS**	CFC DEFINITION	GHS 2017 (REV 7) CLASSIFICATION (H-CODE AND CATEGORY); HAZARD STATEMENT; DEFINITION
Oxidizing gas	Liquified	An oxidizing gas that is liquefied [liquefied gases are gases that, in a packaging under the charged pressure, are partially liquid at 68°F (20°C)].	Any gas which may, generally by providing oxygen, cause or contribute to the combustion of other mate- rial more than air does. H270, Category 1; May cause or intensify fire; oxidizer. Any gas which may, generally by providing oxygen, cause or contribute to the combustion of other mate- rial more than air does. H280, liquefied gas, would also apply.
Pyrophoric	—	A chemical with an autoignition temperature in air, at or below a temperature of 130°F (54°C).	Separate definitions based on physical state; see each category of pyrophoric:
Pyrophoric	Solid	A solid with an autoignition temperature in air, at or below a temperature of 130°F (54°C).	H250, Category 1; Pyrophoric solid; Catches fire spon- taneously if exposed to air. A pyrophoric solid is a solid which, even in small quantities, is liable to ignite within 5 minutes after coming into contact with air. Classification criteria: The solid ignites within 5 minutes of coming into contact with air.
Pyrophoric	Liquid	A liquid with an autoignition temperature in air, at or below a temperature of 130°F (54°C).	H250, Category 1; Pyrophoric liquid; Catches fire spon- taneously if exposed to air: A pyrophoric liquid is a liquid which, even in small quantities, is liable to ignite within 5 minutes after coming into contact with air. Classification criteria: The liquid ignites within 5 minutes when added to an inert carrier and exposed to air, or it ignites or chars a filter paper on contact with air within 5 minutes. Testing is performed at 25 ±2°C and 50 ±5% relative humidity.
Pyrophoric	Gas	A gas with an autoignition temperature in air, at or below a temperature of 130°F (54°C).	H220, Category 1A; Extremely flammable gas.

Frequently asked questions

When is an appliance treated per the manufacturer's instructions instead of Chapter 7 sizing?

If the appliance is other than natural draft, not a Category I vented appliance, or is equipped with power burners, § 701.1.1 requires following the appliance manufacturer’s instructions for combustion/ventilation/dilution air.

Do direct‑vent appliances ever need Chapter 7 combustion air?

No — direct vent appliances are explicitly excluded from Chapter 7 applicability per § 701.1.

What is the quick test to see if indoor combustion air is acceptable?

Use the standard method in § 701.4.1: required room volume = 50 ft³ × (appliance input in 1,000 Btu/h). If the space meets or exceeds that volume (or meets the known‑infiltration method in § 701.4.2), indoor air may be acceptable; otherwise use outdoor methods in § 701.6–§ 701.9.3.

Are Type I clothes dryers covered by Chapter 7?

Type I clothes dryers are an exception to Chapter 7 if provided with makeup air in accordance with § 504.4.1.

What if exhaust fans or kitchen ventilation affect appliance draft?

Provide makeup air as required by § 701.3 so appliance operation isn't compromised.

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