CMC · California Mechanical Code
Which appliances are required to be vented?
Most fuel‑burning appliances must be vented under Chapter 8 of the California Mechanical Code. Low‑ and medium‑heat gas appliances are explicitly required to be vented; §802.2 says all appliances must connect to vents unless they match one of the exceptions listed in §802.2.1 (for example, listed ranges, certain listed small appliances, listed refrigerators, and a few other listed items). Always confirm appliance listing and follow manufacturer instructions and related Chapter 8 provisions.
Last reviewed: July 6, 2026
What the code requires — plain English
The California Mechanical Code requires that the venting of fuel‑burning appliances be governed by Chapter 8 — i.e., the chapter controls which appliances must have vents (§ 801.1) . Low‑heat and medium‑heat gas appliances must be vented under that chapter (§ 801.2) . In general, all appliances must be connected to a venting system except those specifically listed as not required to be vented in § 802.2.1 — the Code’s enumerated exceptions control which appliances may remain unvented (§ 802.2) .
The single most important rule: unless an appliance is specifically listed as not required to be vented in § 802.2.1, it must be connected to a venting system per § 802.2 .
Requirements in detail
Scope and basic rule
- Chapter 8 governs venting of fuel‑burning appliances; see § 801.1 .
- Low‑heat and medium‑heat gas appliances are required to be vented under this chapter; other gas appliances follow NFPA 211 or other applicable standards (§ 801.2) .
- All appliances shall be connected to venting systems except as permitted by the enumerated exceptions in § 802.2.1 (§ 802.2) .
Which appliances are NOT required to be vented (enumerated exceptions)
Section § 802.2.1 lists appliances that are not required to be vented. Key items from that list:
| Appliance (short) | Required to be vented? | Notes / decision‑relevant detail | Code Reference |
|---|---|---|---|
| Listed ranges | No | “Listed” = appliance listed by a recognized testing lab | § 802.2.1 (1) |
| Built‑in domestic cooking units marked for optional venting | No (if so marked) | Manufacturer listing/marking controls | § 802.2.1 (2) |
| Listed hot plates | No | Must be listed for unvented operation | § 802.2.1 (3) |
| Listed Type 1 clothes dryers exhausted per § 504.4 | No (when exhausted per § 504.4) | Must meet exhaust requirements in § 504.4 | § 802.2.1 (4) |
| Single listed booster‑type water heater used only for dishwashing sanitizing rinse in a commercial kitchen (with draft hood intact and mechanical exhaust present; outlet clearances specified) | No (very limited commercial condition) | Draft hood must be unaltered; outlet clearance requirements stated in the exception | § 802.2.1 (5) |
| Listed refrigerators | No | Only if listed for unvented use | § 802.2.1 (6) |
| Counter appliances (listed) | No | Small countertop appliances that are listed | § 802.2.1 (7) |
| Room heaters listed for unvented use | No | Must be listed for unvented use | § 802.2.1 (8) |
| Direct gas‑fired makeup‑air heaters | No | Listed direct gas‑fired makeup‑air equipment | § 802.2.1 (9) |
| Other appliances listed for unvented use and not provided with flue collars | No | Listing and absence of flue collar are the conditions | § 802.2.1 (10) |
| Specialized limited‑input appliances (lab burners, gas lights) | No | Narrow, specialized uses listed as exceptions | § 802.2.1 (11) |
(These items come directly from § 802.2.1; see that section for the full, exact list and precise wording.)
Design / performance requirements when appliances are vented
- Appliances required to be vented must be connected to a venting system designed to convey all flue/vent gases outdoors and to meet appliance draft requirements per manufacturer's instructions (§ 802.3, § 802.3.1, § 802.3.2) — see Chapter 8 for system design and installation requirements .
Exceptions & special cases
- The Code’s primary exceptions to the general venting requirement are the list in § 802.2.1; each item must meet the specific condition (for example, being listed or installed per another CMC section) to qualify for the exception .
- Direct‑vent appliances and appliances with integral vents are treated specially and must be installed per manufacturer instructions and specific Code subsections (see related provisions below) — they are handled under other subsections of § 802.2 et seq. .
- The Code text shown in the controlling sections does not include a numeric aggregate input‑rating limit in § 801.1 / § 801.2 / § 802.2 / § 802.2.1. (A separate provision with an aggregate input threshold appears in the California Plumbing Code at § 509.2.2; that is not one of your specified controlling sections but may be relevant where multiple unvented appliances are installed) .
Common mistakes
- Assuming “no vent” means “no exhaust to outdoors.” The Code’s exceptions are specific: most unvented allowances depend on the appliance being listed for unvented operation or meeting specific installation conditions in the exception language (§ 802.2.1) .
- Overlooking manufacturer listings and instructions. Several exceptions require the appliance to be listed or installed per the manufacturer; listing status is decisive for applicability of the exception (§ 802.2.1) .
- Forgetting other Code cross‑references. The Code permits certain non‑conventional venting (e.g., ventilating hoods for industrial appliances, direct‑vent terminations) but those are handled in other subparts of Chapter 8 and by appliance listings — do not rely solely on the § 802.2.1 list without checking related sections and the manufacturer’s instructions .
Worked example
Scenario: A single‑family kitchen contains:
- a listed gas range,
- a storage‑type gas water heater (listed), and
- a listed refrigerator.
Step 1 — Apply the general rule: all fuel‑burning appliances are governed by Chapter 8 (§ 801.1) and, unless excepted, must be connected to a venting system (§ 802.2) .
Step 2 — Check the exception list in § 802.2.1:
- Listed ranges are specifically not required to be vented under § 802.2.1(1) — so the gas range does not require a building vent/chimney connection by itself; local kitchen ventilation (hood) remains separate code/business practice (§ 802.2.1(1)) .
- Listed refrigerators are listed in § 802.2.1(6) as not required to be vented — so the refrigerator does not require a vent connection (§ 802.2.1(6)) .
- The storage water heater is not listed among the § 802.2.1 exceptions, so it must be connected to a venting system per Chapter 8 (i.e., vented to the outdoors per the venting rules and appliance instructions) (§ 802.2, § 801.2) .
Result: In this scenario, the water heater must be vented; the listed range and listed refrigerator are not required to be vented under § 802.2.1. Always confirm appliance listing statements and installation instructions to verify applicability of an exception (§ 802.2.1) .
Related provisions (select)
- § 801.3 — Appliances fueled by fuels other than gas; NFPA 211 and manufacturer instructions apply .
- § 802.3 — Minimum safe performance; venting systems must convey all flue gases to the outdoors; draft and mechanical draft requirements .
- § 802.2.6 — Direct‑vent appliances (installation per manufacturer instructions) .
- § 802.2.7 — Appliances with integral vents; installation requirements .
- § 701.1 — Combustion air applicability (combustion air rules affect venting/installation) .
- California Plumbing Code § 509.2.2 — (Not in your listed controlling sections) contains an aggregate input‑rating limit that may apply when multiple unvented appliances are installed; consult that section where multiple unvented appliances are present .
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
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 8
CHIMNEYS AND VENTS
801.0 General.
801.1 Applicability. The requirements of this chapter shall govern the venting of fuel-burning appliances.
801.2 Venting of Gas Appliances. Low-heat and medium-heat gas appliances shall be vented in accordance with this chapter. Other gas appliances shall be vented in accordance with NFPA 211 or other applicable standards.
801.3 Appliances Fueled by Other Fuels. Appliances fueled by fuels other than gas shall be vented in accordance with NFPA 211 and the appliance manufacturer’s instructions.
802.0 Venting of Appliances.
802.1 Listing. Type B and Type B-W gas vents shall comply with UL 441, Type L gas vents shall comply with UL 641.
802.1.1 Installation. Listed chimneys and vents shall be installed in accordance with this chapter and the manufacturer’s installation instructions. [NFPA 54:12.2.1]
802.1.2 Prohibited Discharge. Appliance vents shall not discharge into a space enclosed by screens having openings less than [1] ⁄ 4 of an inch (6.4 mm) mesh.
802.2 Connection to Venting Systems. Except as permitted in Section 802.2.1 through Section 802.2.7, all appliances shall be connected to venting systems. [NFPA 54:12.3.1]
802.2.1 Appliances Not Required to be Vented. The following appliances shall not be required to be vented:
(1) Listed ranges.
(2) Built-in domestic cooking units listed and marked for optional venting.
(3) Listed hot plates.
(4) Listed Type 1 clothes dryers exhausted in accordance with Section 504.4.
(5) A single listed booster-type (automatic instantaneous) water heater, when designed and used solely for the sanitizing rinse requirements of a dishwashing machine, provided that the appliance is installed with the draft hood in place and unaltered, if a draft hood is required, in a commercial kitchen having a mechanical exhaust system. [Where installed in this manner, the draft hood outlet shall not be less than 36 inches (914 mm) vertically and 6 inches (152 mm) horizontally from any surface other than the appliance.]
(6) Listed refrigerators.
(7) Counter appliances.
(8) Room heaters listed for unvented use.
(9) Direct gas-fired makeup-air heaters.
(10)Other appliances listed for unvented use and not provided with flue collars.
(11)Specialized appliances of limited input such as laboratory burners or gas lights. [NFPA 54:12.3.2]
CMC § 1.11.0. High 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 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 8
CHIMNEYS AND VENTS
801.0 General.
801.1 Applicability. The requirements of this chapter shall govern the venting of fuel-burning appliances.
801.2 Venting of Gas Appliances. Low-heat and medium-heat gas appliances shall be vented in accordance with this chapter. Other gas appliances shall be vented in accordance with NFPA 211 or other applicable standards.
801.3 Appliances Fueled by Other Fuels. Appliances fueled by fuels other than gas shall be vented in accordance with NFPA 211 and the appliance manufacturer’s instructions.
802.0 Venting of Appliances.
802.1 Listing. Type B and Type B-W gas vents shall comply with UL 441, Type L gas vents shall comply with UL 641.
802.1.1 Installation. Listed chimneys and vents shall be installed in accordance with this chapter and the manufacturer’s installation instructions. [NFPA 54:12.2.1]
CMC § 802.3 High relevance — show source text
802.3 Minimum Safe Performance. Venting systems shall be designed and constructed to convey all flue and vent gases to the outdoors. [NFPA 54:12.1]
802.3.1 Appliance Draft Requirements. A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer’s instructions. [NFPA 54:12.4.1]
802.3.2 Appliance Venting Requirements. Appliances required to be vented shall be connected to a vent
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CHIMNEYS AND VENTS
ing system designed and installed in accordance with the provisions of Section 802.4 through Section 802.15.
[NFPA 54:12.4.2]
802.3.3 Mechanical Draft Systems. Mechanical draft systems shall be listed in accordance with UL 378 and installed in accordance with both the appliance and the mechanical draft system manufacturer’s installation instructions. [NFPA 54:12.4.3.1]
802.3.3.1 Venting. Appliances requiring venting shall be permitted to be vented by means of mechanical draft systems of either forced or induced draft design. [NFPA 54:12.4.3.2]
802.3.3.2 Leakage. Forced draft systems and all portions of induced draft systems under positive pressure during operation shall be designed and installed so as to prevent leakage of flue or vent gases into a building. [NFPA 54:12.4.3.3]
802.3.3.3 Vent Connectors. Vent connectors
serving appliances vented by natural draft shall not be connected into any portion of mechanical draft systems operating under positive pressure. [NFPA 54:12.4.3.4]
802.3.3.4 Operation. Where a mechanical draft system is employed, provision shall be made to prevent the flow of gas to the main burners when the draft system is not performing so as to satisfy the operating requirements of the appliance for safe performance. [NFPA 54:12.4.3.5]
802.3.4 Ventilating Hoods and Exhaust Systems. Where automatically operated appliances, other than food service appliances, are vented through a ventilating hood or exhaust system equipped with a damper or with a power means of exhaust, provisions shall be made to allow the flow of gas to the main burners only when the damper is open to a position to properly vent the appliance and when the power means of exhaust is in operation. [NFPA 54:12.4.4.1]
802.3.5 Circulating Air Ducts, Above-Ceiling Air- Handling Spaces, and Furnace Plenums. Venting systems shall not extend into or pass through any fabricated air duct or furnace plenum. [NFPA 54:12.4.5.1]
802.3.6 Above-Ceiling or Nonducted Air Han- dling System. Where a venting system passes through an above-ceiling air space or other nonducted portion of an air-handling system, it shall conform to one of the following requirements:
CMC § 802.2.3 High relevance — show source text
802.2.3 Adjacent Room or Space. Where the calculation includes the volume of an adjacent room or space, the room or space in which the appliances are installed shall be directly connected to the adjacent room or space by a doorway, archway, or other opening of comparable size that cannot be closed. [NFPA 54:12.3.2.2]
802.2.4 Ventilating Hoods. The use of ventilating hoods and exhaust systems to vent appliances shall be limited to industrial appliances and appliances installed in commercial applications. [NFPA 54:12.3.3]
802.2.5 Well-Ventilated Spaces. The flue gases from industrial-type appliances shall not be required to be vented to the outdoors where such gases are discharged into a large and well-ventilated industrial space. [NFPA 54:12.3.4]
802.2.6 Direct Vent Appliances. Listed direct vent appliances shall be installed in accordance with the manufacturer’s installation instructions. [NFPA 54:12.3.5.1]
802.2.6.1 Through-the-Wall Vent Terminations. Through-the-wall vent terminations for listed direct vent appliances shall be in accordance with Section 802.8.1. [NFPA 54:12.3.5.2]
802.2.7 Appliances with Integral Vents. Appliances incorporating integral venting means shall be installed in accordance with Section 802.8.1. [NFPA 54:12.3.6]
802.2.8 Incinerators, Commercial–Industrial. Incinerators shall be vented in accordance with NFPA 82.
[NFPA 54:12.3.7]
802.3 Minimum Safe Performance. Venting systems shall be designed and constructed to convey all flue and vent gases to the outdoors. [NFPA 54:12.1]
802.3.1 Appliance Draft Requirements. A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer’s instructions. [NFPA 54:12.4.1]
802.3.2 Appliance Venting Requirements. Appliances required to be vented shall be connected to a vent
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CHIMNEYS AND VENTS
ing system designed and installed in accordance with the provisions of Section 802.4 through Section 802.15.
[NFPA 54:12.4.2]
802.3.3 Mechanical Draft Systems. Mechanical draft systems shall be listed in accordance with UL 378 and installed in accordance with both the appliance and the mechanical draft system manufacturer’s installation instructions. [NFPA 54:12.4.3.1]
802.3.3.1 Venting. Appliances requiring venting shall be permitted to be vented by means of mechanical draft systems of either forced or induced draft design. [NFPA 54:12.4.3.2]
802.3.3.2 Leakage. Forced draft systems and all portions of induced draft systems under positive pressure during operation shall be designed and installed so as to prevent leakage of flue or vent gases into a building. [NFPA 54:12.4.3.3]
CMC § 509.0 High relevance — show source text
509.0 Venting of Appliances. 509.1 Listing. Type B and Type B-W gas vents shall comply with UL 441, and Type L gas vents shall comply with UL 641. 509.1.1 Installation. Listed chimneys and vents shall be installed in accordance with Section 509.0 and the manufacturers’ installation instructions. [NFPA 54:12.2.1] 509.1.2 Prohibited Discharge. Appliance vents shall not discharge into a space enclosed by screens having openings less than [1] ⁄ 4 of an inch (6.4 mm) mesh. 509.2 Connection to Venting Systems. Except as permitted in Section 509.2.1 through Section 509.2.7, all appliances shall be connected to venting systems. [NFPA 54:12.3.1] 509.2.1 Appliances Not Required to be Vented. The following appliances shall not be required to be vented:
(1) A single listed booster-type (automatic instantaneous) water heater, when designed and used solely for the sanitizing rinse requirements of a dishwashing machine, provided that the appliance is installed with the draft hood in place and unaltered, if a draft hood is required, in a commercial kitchen having a mechanical exhaust system. [Where installed in this
manner, the draft hood outlet shall not be less than 36 inches (914 mm) vertically and 6 inches (152 mm) horizontally from any surface other than the appliance.] [NFPA 54:12.3.2(5)]
(2) Other appliances listed for unvented use and not provided with flue collars. [NFPA 54:12.3.2(10)] 509.2.2 Maximum Input Rating. Where any or all of the appliances in Section 509.2.1(1) and Section 509.2.1(2) are installed so the aggregate input rating exceeds 20 (Btu/h)/ft [3] (207 W/m [3] ) of room or space in which it is installed, one or more shall be provided with venting systems or other approved means for conveying the vent gases to the outdoors so that the aggregate input rating of the remaining unvented appliances does not exceed 20 (Btu/h)/ft [3] (207 W/m [3] ). [NFPA 54:12.3.2.1] 509.2.3 Adjacent Room or Space. Where the calculation includes the volume of an adjacent room or space, the room or space in which the appliances are installed shall be directly connected to the adjacent room or space by a doorway, archway, or other opening of comparable size that cannot be closed. [NFPA 54:12.3.2.2]
509.2.4 Ventilating Hoods. The use of ventilating hoods and exhaust systems to vent appliances shall be limited to industrial appliances and appliances installed in commercial applications. [NFPA 54:12.3.3] 509.2.5 Well-Ventilated Spaces. The flue gases from industrial-type appliances shall not be required to be vented to the outdoors where such gases are discharged into a large and well-ventilated industrial space. [NFPA 54:12.3.4]
509.2.6 Direct-Vent Appliances. Listed direct vent appliances shall be installed in accordance with the manufacturer’s installation instructions. [NFPA 54:12.3.5.1]
CMC § 509.2.1 High relevance — show source text
** Where any or all of the appliances in Section 509.2.1(1) and Section 509.2.1(2) are installed so the aggregate input rating exceeds 20 (Btu/h)/ft [3] (207 W/m [3] ) of room or space in which it is installed, one or more shall be provided with venting systems or other approved means for conveying the vent gases to the outdoors so that the aggregate input rating of the remaining unvented appliances does not exceed 20 (Btu/h)/ft [3] (207 W/m [3] ). [NFPA 54:12.3.2.1] 509.2.3 Adjacent Room or Space. Where the calculation includes the volume of an adjacent room or space, the room or space in which the appliances are installed shall be directly connected to the adjacent room or space by a doorway, archway, or other opening of comparable size that cannot be closed. [NFPA 54:12.3.2.2]
509.2.4 Ventilating Hoods. The use of ventilating hoods and exhaust systems to vent appliances shall be limited to industrial appliances and appliances installed in commercial applications. [NFPA 54:12.3.3] 509.2.5 Well-Ventilated Spaces. The flue gases from industrial-type appliances shall not be required to be vented to the outdoors where such gases are discharged into a large and well-ventilated industrial space. [NFPA 54:12.3.4]
509.2.6 Direct-Vent Appliances. Listed direct vent appliances shall be installed in accordance with the manufacturer’s installation instructions. [NFPA 54:12.3.5.1]
509.2.6.1 Through-the-Wall Vent Termination. Through-the-wall vent terminations for listed directvent appliances shall be in accordance with Section 509.8.1. [NFPA 54:12.3.5.2]
509.2.7 Appliances with Integral Vents. Appliances incorporating integral venting means shall be installed in accordance with Section 509.8. [NFPA 54:12.3.6] 509.3 Minimum Safe Performance. Venting systems shall be designed and constructed to convey all flue and vent gases to the outdoors. [NFPA 54:12.1] 509.3.1 Appliance Draft Requirements. A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer’s instructions.
[NFPA 54:12.4.1]
509.3.2 Appliance Venting Requirements. Appliances required to be vented shall be connected to a venting system designed and installed in accordance with the provisions of Section 509.4 through Section 509.15.
[NFPA 54:12.4.2] 509.3.3 Mechanical Draft Systems. Mechanical draft systems shall be listed in accordance with UL 378 and installed in accordance with both the appliance and the mechanical draft system manufacturer’s installation instructions. [NFPA 54:12.4.3.1]
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WATER HEATERS
CMC § 8.13.6 High relevance — show source text
[ASHRAE 15:8.13.6]
»
(1) Operated, where occupied, to supply not less than 0.5 CFM/ft [2] [2.54 L/(s•m [2] )] of machinery room area or 20 cubic feet per minute (9.44 L/s) per person.
(2) Operable, where occupied at a volume required to not exceed the higher of a temperature rise of 18°F (10°C) above inlet air temperature or a maximum temperature of 122°F (50°C).
1106.4 Natural Ventilation. When a refrigerating system is located outdoors more than 20 feet (6096 mm) from building openings and is enclosed by a penthouse, lean-to, or other open structure, natural or mechanical ventilation shall be provided. The requirements for such natural ventilation shall be in accordance with the following:
(1) The free-aperture cross section for the ventilation of a machinery room shall be not less than as determined in accordance with Equation 1106.4.
F = √ G (Equation 1106.4)
Where:
F = The free opening area, ft [2] (m [2] ).
G = The mass of refrigerant in the largest system, any part of which is located in the machinery room, pounds.
For SI units: 1 square foot = 0.0929 m [2], 1 pound = 0.453 kg
(2) Locations of the gravity ventilation openings shall be based on the relative density of the refrigerant to air.
[ASHRAE 15:8.14]
1106.5 Combustion Air. No open flames that use combustion air from the machinery room shall be installed where refrigerant is used. Combustion equipment shall not be installed in the same machinery room with refrigerant-containing equipment except under one of the following conditions:
(1) Combustion air shall be ducted from outside the machinery room and sealed in such a manner as to prevent refrigerant leakage from entering the combustion chamber.
(2) A refrigerant detector, that is in accordance with Section 1106.2.5, shall be installed to automatically shut down the combustion process in the event of refrigerant leak age.
Exception: Machinery rooms where carbon dioxide (R-744) or water (R-718) is the refrigerant.
1106.6 Ventilation Intake. Makeup air intakes to replace the exhaust air shall be provided to the refrigeration machinery room directly from outside the building. Intakes shall be located as required by other sections of the code and fitted with backdraft dampers or other approved flow-control means to prevent reverse flow. Distribution of makeup air shall be arranged to provide thorough mixing within the refrigeration machinery room to prevent short circuiting of the makeup air directly to the exhaust.
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REFRIGERATION
1106.11.6.1 Mechanical Ventilation. The machinery room shall have a mechanical ventilation system in accordance with Section 1106.11.11. The mechanical ventilation system shall:
(1) Run continuously, and failure of the mechanical ventilation system actuates an alarm, or
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 § 8-902.5 High relevance — show source text
8-902.5 Combustion air.
8-902.5.1 All fuel-burning appliances and equipment shall be provided a sufficient supply of air for proper fuel combustion, ventilation and draft hood dilution.
8-902.5.2 The enforcing agency may require operational tests for combustion air systems which do not comply with applicable requirements of the regular code.
8-902.6 Venting of appliances.
8-902.6.1 Every appliance required to be vented shall be connected to an approved venting system. Venting systems shall develop a positive flow adequate to convey all combustion products to the outside atmosphere.
8-902.6.2 Masonry chimneys in structurally sound condition may remain in use for all fuel-burning appliances, provided the flue is evaluated and documentation provided that the masonry and grout are in good condition. Terra cotta chimneys and Type C metallic vents installed in concealed spaces shall not remain in use unless otherwise mitigated and approved on a case-by-case basis.
8-902.6.3 The enforcing agency may require operational tests for venting systems which do not comply with applicable requirements of the regular code.
8-902.7 Ducts.
8-902.7.1 New ducts shall be constructed and installed in accordance with applicable requirements of the regular code.
8-902.7.2 Existing duct systems which do not comply with applicable requirements of the regular code and do not, in the opinion of the enforcing agency, constitute a safety or health hazard may remain in use.
8-902.8 Ventilating systems.
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MECHANICAL, PLUMBING AND ELECTRICAL REQUIREMENTS
8-902.8.1 Ventilating systems shall be installed so that no safety hazard is created.
8-902.8.2 Grease hoods and grease hood exhaust systems shall be furnished and installed in accordance with applicable requirements of the regular code. Existing systems which are altered shall comply with the regular code.
8-902.9 Miscellaneous equipment requirements.
8-902.9.1 The following appliances and equipment shall be installed so that no safety hazard is created: warm air furnaces, space heating equipment, vented decorative appliances, floor furnaces, vented wall furnaces, unit heaters, room heaters, absorption units, refrigeration equipment, duct furnaces, infrared radiant heaters, domestic incinerators, miscellaneous heat-producing appliances and water heaters.
8-902.9.2 Storage-type water heaters shall be equipped with a temperature- and pressure-relief valve in accordance with applicable requirements of the regular code.
SECTION 8-903 — PLUMBING
8-903.1 General. Plumbing systems shall comply with the regular code unless otherwise noted.
8-903.1.1 The provisions of the CHBC shall apply to the acceptance, location, installation, alteration, repair, relocation, replacement or addition of any plumbing system or equipment within or attached to a historical building.
8-903.1.2 Existing systems which do not, in the opinion of the enforcing agency, constitute a safety hazard may remain in use.
8-903.1.3 The enforcing agency may approve any alternative to these regulations which achieves reasonably equivalent life safety.
8-903.2 Residential occupancies.
CMC § 517.1 High relevance — show source text
517.1 Venting Application. Venting requirements of solidfuel cooking operations shall be determined in accordance with Section 517.1.1 through Section 517.1.6. [NFPA 96:15.1] 517.1.1 Natural Draft. Where solid-fuel cooking equipment is required by the manufacturer to have a natural draft, the vent shall comply with Section 517.4. [NFPA 96:15.1.1] 517.1.2 System Compliance. Where the solid-fuel cooking equipment has a self-contained top, is the appliance to be vented in an isolated space (except for a single water heater with its own separate vent), has a separate makeup air system, and is provided with supply and return air (not supplied or returned from other spaces), the system shall comply with Section 517.4 and Section 517.6.
[NFPA 96:15.1.2]
517.1.3 Makeup Air System. Where the solid-fuel cooking equipment is located in a space with other vented equipment, all vented equipment shall have an exhaust system interlocked with a makeup air system for the space per Section 517.6. [NFPA 96:15.1.4]
517.1.4 Natural Draft Ventilation Systems. Natural draft ventilation systems and power-exhausted ventilation systems shall comply with Section 517.3, Section 517.4, and Section 517.6. [NFPA 96:15.1.5] 517.1.5 Opening Requirements. Where a solid-fuel cooking appliance allows effluent to escape from the appliance opening, this opening shall be covered by a hood and
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EXHAUST SYSTEMS
an exhaust system that meets the requirements of Section 517.3, Section 517.4, and Section 517.6. [NFPA 96:15.1.6]
517.1.6 Spark Arresters. Solid-fuel cooking operations shall have spark arresters to minimize the passage of airborne sparks and embers into plenums and ducts. Where the solid-fuel cooking operation is not located under a hood, a spark arrester shall be provided to minimize the passage of sparks and embers into flues and chimneys.
[NFPA 96:15.1.7, 15.1.8]
517.2 Location of Appliances. For cooking operations in buildings, every appliance shall be located with respect to building construction and other equipment so as to permit access to the appliance. [NFPA 96:15.2.1]
517.2.1 Prohibited Location. Solid-fuel cooking appliances shall not be installed in confined spaces. [NFPA 96:15.2.2]
Exception: Solid-fuel cooking appliances listed for installation in confined spaces such as alcoves shall be installed in accordance with the terms of the listing and the manufacturer’s instructions. [NFPA 96:15.2.3]
517.2.2 Flammable Vapors. Solid-fuel cooking appliances shall not be installed in any location where gasoline or any other flammable vapors or gases are present. [NFPA 96:15.2.4]
CMC § 10.4.2 High relevance — show source text
(3) Unlisted clothes dryers shall be installed with clearances to combustible material of not less than 18
inches (457 mm). Combustible floors under unlisted clothes dryers shall be protected in an approved manner. {NFPA 54:10.4.2}
908.3.2 Exhausting to the Outdoors. Type 1 and Type 2 clothes dryers shall be exhausted to the outside air in accordance with Section 504.4. {NFPA 54:10.4.3}
908.3.3 Multiple-Family or Public Use. All clothes dryers installed for multiple-family or public use shall be installed as specified for a Type 2 clothes dryer under Section 504.4.3.1. [NFPA 54:10.4.7]
909.0 Conversion Burners.
909.1 General. Installation of conversion burners shall con form to CSA Z21.8. [NFPA 54:10.5]
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shall be permitted to be an integral part of the vented wall furnace, as illustrated in Figure 907.2.1. The stud space in which the vented wall furnace is installed shall be ventilated at the first ceiling level by installation of the ceiling plate spacers furnished with the gas vent. Firestop spacers shall be installed at each subsequent ceiling or floor level penetrated by the vent. [NFPA 54:10.25.2.2]
907.2.2 Direct Vent Wall Furnaces. Direct vent wall
furnaces shall be installed with the combustion air intake
terminal outdoors. [NFPA 54:10.25.2.3]
907.2.3 Panels, Grilles, and Access Doors. Panels, grilles, and access doors that are required to be removed for normal servicing operations shall not be attached to the building. For additional information on the venting of wall furnaces, see Section 802.0. [NFPA 54:10.25.2.4]
For SI units: 1 inch = 25.4 mm
FIGURE 907.2.1
INSTALLATION OF TYPE B-W GAS VENTS FOR
VENTED WALL FURNACES
[NFPA 54: FIGURE 10.25.2.2]
907.3 Location. Wall furnaces shall be located so as not to cause a hazard to walls, floors, curtains, furniture, or doors. Wall furnaces installed between bathrooms and adjoining rooms shall not circulate air from bathrooms to other parts of the building. [NFPA 54:10.25.3]
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INSTALLATION OF SPECIFIC APPLIANCES
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910.0 Burner Assemblies.
910.1 Oil Burners. Oil burners shall comply with UL 296 and installed in accordance with the manufacturer’s installa tion instructions.
910.2 Gas Burners. Commercial gas burners shall comply with UL 295 and installed in accordance with the manufac turer’s installation instructions.
911.0 Decorative Appliances for Installation in Vented Fireplaces.
CMC § 802.10.1.1 High relevance — show source text
VENT, ATTIC . . . . . . . . . . . . . . . . . . .802.10.1.1, 802.10.1.2
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INDEX
VENT, GAS . . . . . . . . . . . . . . .224.0, 802.4, 802.6, 802.6.2,
802.6.2.1, 802.6.2.2
VENT, GAS CONNECTORS . . . . . . . . . . .(see Connectors,
gas vent) VENT DAMPERS . . . . . . . . . . . . . . . . . . . . .(see Dampers)
VENT SIZING
Category I appliances . . . . . . . . . . . . .802.6.2.1, 803.0
Multiple appliances . . . . . . . . . . . . . . . . . . . . . . .803.2,
Table 803.2(1)–Table 803.2(9)
Multistory . . . . . . . . . . . . . . . . . . . . .802.6.3, 802.6.3.2,
803.2.16
Single appliance . . . . .802.7.4(1)(b), 802.10.2.1, 803.1,
Table 803.1.2(1)–Table 803.1.2(6)
VENTED
Decorative appliances . . . . . . . . . . . . . . . .224.0, 911.0,
Table 802.4
Equipment not
required to be . . . . . . . . . . . . . . . . . . . . . . . . .802.2.1
Fireplaces . . . . . . . . . . . . . . . . . . . . . . .912.0, E 602.0,
Table 1308.3.1
Wall furnace . . . . . . . . . . . . . .224.0, 907.2, Table 802.4
VENTED APPLIANCE CATEGORIES
Category I . . . . . . . . . . . . . . . .224.0, 701.1.1, 802.6.2.1,
802.6.3, 802.10, 802.10.1.1,
802.10.3.2, 803.0,
Appendix F, Table 802.4,
Table 803.1.2(1)–Table 803.1.2(4),
Table 803.2(1)–Table 803.2(4)
Category II . . . . . . . . . . . . . . . . . . . . .224.0, 802.6.2.3,
802.9, 802.11, Table 802.4
Category III . . . . . . . . . . . . . . . . . . . . .224.0, 802.6.2.3,
802.9.1, Table 802.4
Frequently asked questions
Which section is the single best reference for whether an appliance must be vented?
Check § 802.2 (all appliances shall be connected to venting systems except as permitted) and then the enumerated exceptions in § 802.2.1 .
Does “listed” mean the appliance can be unvented?
Only if the appliance is listed for unvented use (or is specifically listed in an exception). The Code’s exceptions in § 802.2.1 often require a listing or specific marking .
Are direct‑vent appliances exempt from venting rules?
Direct‑vent appliances are handled specially and must be installed per the manufacturer and the relevant direct‑vent subsections (see § 802.2.6 and related text) — they are not covered simply by § 802.2.1’s general exceptions .
If multiple “unvented” appliances are installed, could there be an aggregate limit?
That numeric aggregate limit is not in the four controlling sections you specified. A related aggregate‑input rule appears in the California Plumbing Code at § 509.2.2; consult that section and the AHJ when multiple unvented appliances are installed .
Where do I find the detailed venting design rules?
Venting system design, draft, mechanical draft system requirements, and performance criteria are in Chapter 8 subsections (for example § 802.3, § 802.3.1, § 802.3.2) — follow those and manufacturer instructions .
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