CMC · California Mechanical Code
Wall furnaces — application, installation, location, air requirements
Wall furnaces must be listed and installed exactly per their listing and manufacturer instructions. Vent type (e.g., Type B‑W single‑story vs multistory) controls which floors they can serve; direct‑vent units must take combustion air from outdoors; and combustion‑air and circulating‑air provisions called out in § 701.0 must be followed.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Wall furnaces must be listed to the applicable standard and installed per the manufacturer’s instructions — you must follow § 907.1 and § 907.2. Vented wall‑furnace venting is limited by the type of gas‑vent listing (for example, a Type B‑W vent listed for single‑story use may only be used in a single‑story structure or the top story) per § 907.2.1. Direct‑vent wall furnaces must draw combustion air from outdoors, and combustion and circulating air must be provided in accordance with § 701.0, as required by § 907.2.2 and § 907.4. Oil‑fired wall furnaces have their own listing/standard requirements under § 907.5.
The single most important rule: a wall furnace must be a listed appliance installed exactly as its listing and the manufacturer require — vent type and combustion‑air provisions control where and how it may be installed (see § 907.1, § 907.2, § 907.4).
Requirements in detail
Applicability and listing
- A wall furnace must be listed to ANSI Z21.86/CSA 2.32. See § 907.1.
- Oil‑fired wall furnaces must comply with UL 730 and be installed per the manufacturer. See § 907.5.
Installation (general)
- All wall furnaces shall be installed in accordance with the manufacturer’s installation instructions. See § 907.2.
- If a wall furnace is installed in or attached to combustible material, the unit must be listed for such installation. See § 907.2.
- Panels, grilles, and access doors that must be removed for normal service shall not be attached to the building (they need to be removable) — see § 907.2.3.
Venting rules
- Vented wall furnaces connected to a Type B‑W gas vent that is listed only for single‑story installation may be installed only in single‑story buildings or in the top story of multistory buildings. If the Type B‑W is listed for multistory use, it may be used in single‑ or multistory buildings. See § 907.2.1.
- Type B‑W gas vents must be attached directly to a solid header plate that serves as a firestop; stud spaces used for the vent must be ventilated per the vent manufacturer’s plate/spacer instructions and firestop spacers installed at each floor/ceiling penetration. See § 907.2.1 and the figure for Type B‑W installation.
Combustion and circulating air
- Combustion and circulating air for wall furnaces must be provided in accordance with Section 701.0 (combustion‑air provisions) — see § 907.4. The CMC directs you to § 701.0 for the sizing/location/combination rules for indoor/outdoor air sources and engineered or mechanical supply methods. See § 907.4 and § 701.0.
Decision‑relevant dimensions/values and where to look in the code:
| Decision or value needed | What to check / value | Code Reference |
|---|---|---|
| Required listing for gas wall furnaces | ANSI Z21.86 / CSA 2.32 | § 907.1 |
| Installation authority | Manufacturer’s installation instructions; unit listed for combustible attachment if installed on combustibles | § 907.2 |
| Venting: Type B‑W single‑story vs multistory | Type B‑W listed for single story → only single‑story or top story; multistory listing → permitted in all stories | § 907.2.1 |
| Vent attachment / firestop | Gas vent must be attached to a solid header plate serving as a firestop; stud space ventilation and firestop spacers per vent instructions | § 907.2.1 and Figure 907.2.1 |
| Direct‑vent combustion air | Direct‑vent units must have combustion air intake outdoors | § 907.2.2 |
| Panels/grilles for servicing | Removable for service and not attached to the building | § 907.2.3 |
| Combustion & circulating air sizing/location | Follow § 701.0 (indoor/outdoor/combination/engineered methods) | § 907.4 → § 701.0 |
| Oil‑fired wall furnace standard | UL 730 | § 907.5 |
Location constraints
- Wall furnaces shall be located so they do not create hazards to walls, floors, curtains, furniture or doors; placement must avoid exposing combustibles to heat or blocking egress. See § 907.3.
- A wall furnace installed between a bathroom and an adjoining room shall not circulate bathroom air to other parts of the building (avoid cross‑contamination). See § 907.3.
Exceptions & special cases
- Vented wall furnaces have different allowances depending on whether the Type B‑W gas vent is listed for single‑story or multistory installation — you must use the vent’s listing to decide permissible building locations per § 907.2.1.
- Direct‑vent wall furnaces are a special case: their combustion‑air intake must be outdoors (they are not permitted to rely on indoor building air for combustion) — see § 907.2.2.
- If a furnace is installed in or attached to combustible material, it must be specifically listed for that application; unlisted installations on combustible surfaces are not permitted — see § 907.2.
Common mistakes
- Assuming any gas vent connector can be used anywhere. The vent’s listing (single‑story vs multistory) controls allowable installation stories — check § 907.2.1.
- Installing a direct‑vent unit without routing its combustion‑air intake outdoors — direct‑vent units specifically require outdoor combustion air per § 907.2.2.
- Attaching service panels or grilles to the building (they must be removable and not attached) — see § 907.2.3.
- Forgetting to provide combustion and circulating air per § 701.0; the wall furnace section defers to § 701.0 for those sizing and opening rules (do not guess the quantities). See § 907.4.
Worked example — concrete scenario
Scenario: You are installing a listed vented gas wall furnace in a two‑story house. The gas vent supplied with the unit is a Type B‑W vent that is listed only for single‑story installation.
Apply the code:
- Because the Type B‑W vent is listed only for single‑story use, you may install the vented wall furnace only in a single‑story building or in the top story of a multistory building. In this two‑story house you may install it only on the second (top) floor, not on the first floor, per § 907.2.1.
- Ensure the gas vent is attached directly to a solid header plate that serves as a firestop at the penetration, and install required ceiling/floor firestop spacers and stud space ventilation as the vent instructions/figure indicate (Figure 907.2.1) — see § 907.2.1 and Figure 907.2.1.
- Provide combustion & circulating air per § 701.0; because § 907.4 defers to § 701.0, check § 701.0 for whether indoor openings or outdoor ducts are required for the appliance capacity and room volume. (The detailed air‑sizing numbers and opening sizes are in § 701.0, which you must consult directly.)
If instead the supplied Type B‑W vent were listed for multistory use, the same unit could be installed on either the first or second floor (single‑ or multistory installation permitted) per § 907.2.1.
Related provisions
- Combustion and indoor/outdoor air rules — § 701.0 (combustion‑air requirements; see also §§ 701.4–701.12 for details).
- Venting of appliances and gas‑vent rules — § 802.0 (general venting/vent types and requirements, referenced by § 907.2.3).
- Appliance venting details including Type B‑W and gas‑vent specifics — see the parts of Chapter 8 (Table 802.4, § 802.6, etc.).
(If you need the numeric combustion‑air openings, indoor‑volume thresholds, or exact opening sizes called out in § 701.0, those specific values are contained in § 701.0 and were not included in the materials I retrieved for this summary — consult § 701.0 directly for the exact formulas and opening sizes.)
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 907.0 High relevance — show source text
TABLE OF CONTENTS
907.0 Wall Furnaces. . . . . . . . . . . . . . . . 204
907.1 Application . . . . . . . . . . . . . . . . . . 204
907.2 Installation . . . . . . . . . . . . . . . . . . 204
907.3 Location . . . . . . . . . . . . . . . . . . . . 205
907.4 Combustion and Circulating Air . . 205
907.5 Oil-Fired Wall Furnaces . . . . . . . . 205
908.0 Clothes Dryers . . . . . . . . . . . . . . . 205
908.1 Application . . . . . . . . . . . . . . . . . . 205
908.2 Electric Clothes Dryers . . . . . . . . . 205
908.3 Gas-Fired Clothes Dryers. . . . . . . 205
909.0 Conversion Burners . . . . . . . . . . . 205
909.1 General. . . . . . . . . . . . . . . . . . . . . 205
910.0 Burner Assemblies . . . . . . . . . . . . 206
910.1 Oil Burners . . . . . . . . . . . . . . . . . . 206
910.2 Gas Burners . . . . . . . . . . . . . . . . . 206
911.0 Decorative Appliances for Installation in Vented Fireplaces. . . 206
911.1 Application . . . . . . . . . . . . . . . . . . 206
911.2 Prohibited Installations . . . . . . . . . 206
911.3 Installation . . . . . . . . . . . . . . . . . . 206
911.4 Fireplace Screens. . . . . . . . . . . . . 206
912.0 Gas Fireplaces, Vented . . . . . . . . 206
912.1 Application . . . . . . . . . . . . . . . . . . 206
912.2 Reserved . . . . . . . . . . . . . . . . . . . 206
912.3 Installation . . . . . . . . . . . . . . . . . . 206
912.4 Combustion and Circulating Air . . . 206
913.0 Factory-Built Fireplaces and Fireplace Stoves. . . . . . . . . . . . . . 206
913.1 Factory-Built Fireplaces . . . . . . . . 206
913.2 Fireplace Stoves. . . . . . . . . . . . . . 206
913.3 Fireplace Accessories . . . . . . . . . 206
914.0 Non-Recirculating Direct Gas-Fired Industrial Air Heaters. . . 206
914.1 Application . . . . . . . . . . . . . . . . . . 206
914.2 Prohibited Installations . . . . . . . . . 206
914.3 Installation . . . . . . . . . . . . . . . . . . 206
914.4 Clearance from Combustible
Materials . . . . . . . . . . . . . . . . . . . . 207
CMC § 10.10.13 High relevance — show source text
[NFPA 54:10.10.13]
906.14 Oil-Fired Floor Furnaces. Oil-fired floor furnaces shall comply with UL 729 and installed in accordance with the manufacturer’s installation instructions.
907.0 Wall Furnaces.
907.1 Application. Wall furnaces shall be listed in accordance with ANSI Z21.86/CSA 2.32. [NFPA 54:10.25.1]
907.2 Installation. Wall furnaces shall be installed in accor dance with the manufacturer’s installation instructions. Wall
furnaces installed in or attached to combustible material shall be listed for such installation. [NFPA 54:10.25.2.1]
907.2.1 Vented Wall Furnaces. Vented wall furnaces connected to a Type B-W gas vent system listed only for a single story shall be installed only in single-story buildings or the top story of multistory buildings. Vented wall furnaces connected to a Type B-W gas vent system listed for installation in multistory buildings shall be permitted to be installed in single-story or multistory buildings. Type B-W gas vents shall be attached directly to a solid header plate that serves as a firestop at that point and that
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INSTALLATION OF SPECIFIC APPLIANCES
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907.4 Combustion and Circulating Air. Combustion and circulating air shall be provided in accordance with Section 701.0. [NFPA 54:10.25.4]
907.5 Oil-Fired Wall Furnaces. Oil-fired wall furnaces
shall comply with UL 730 and installed in accordance with the manufacturer’s installation instructions.
908.0 Clothes Dryers.
908.1 Application. Clothes dryers shall be listed in accordance with ANSI Z21.5.1/CSA 7.1 for Type I clothes dryers or ANSI Z21.5.2/CSA 7.2 for Type II clothes dryers. [NFPA 54:10.4.1]
908.2 Electric Clothes Dryers. Commercial electric clothes dryers shall comply with UL 1240 and installed in accordance with the manufacturer’s installation instructions.
Residential and coin-operated electric clothes dryers shall comply with UL 2158 and installed in accordance with the manufacturer’s installation instructions.
908.3 Gas-Fired Clothes Dryers. Gas-fired clothes dryers shall comply with Section 908.3.1 through Section 908.3.3.
908.3.1 Clearance. The installation of clothes dryers shall comply with the following requirements:
(1) Listed Type 1 clothes dryers shall be installed with a clearance of not less than 6 inches (152 mm) from adjacent combustible material. Clothes dryers listed for installation at reduced clearances shall be
installed in accordance with their listing and the manufacturer’s installation instructions. Type 1 clothes dryers installed in closets shall be listed for such installation.
CMC § 4.9 High relevance — show source text
A copper pan shall be made of not less than 16 ounces per square foot (oz/ft [2] ) (4.9 kg/m [2] ) sheet copper. The pan shall be anchored in place so as to prevent floating, and the walls shall extend at least 4 inches (102 mm) above the ground level with at least a 6 inches (152 mm) clearance on all sides, except on the control side, which shall have at least an 18 inch (457 mm) clearance. [NFPA 54:10.10.10] 906.11 Wind Protection. Floor furnaces shall be protected, where necessary, against severe wind conditions. [NFPA 54:10.10.11]
906.12 Upper Floor Installations. Floor furnaces shall be permitted to be installed in an upper floor, provided the furnace assembly projects below into a utility room, closet, garage, or similar nonhabitable space. In such installations, the floor furnace shall be enclosed completely (entirely separated from the nonhabitable space) with means for air intake to meet the provisions of Section 701.0, with access for servicing, minimum furnace clearances of 6 inches (152 mm) to all sides and bottom, and with the enclosure constructed of Portland cement plaster or metal lath or other noncombustible material. [NFPA 54:10.10.12]
906.13 First Floor Installation. Floor furnaces installed in the first or ground floors of buildings shall not be required to be enclosed unless the basements of these buildings have been converted to apartments or sleeping quarters, in which case the floor furnace shall be enclosed as specified for upper floor installations and shall project into a nonhabitable space.
[NFPA 54:10.10.13]
906.14 Oil-Fired Floor Furnaces. Oil-fired floor furnaces shall comply with UL 729 and installed in accordance with the manufacturer’s installation instructions.
907.0 Wall Furnaces.
907.1 Application. Wall furnaces shall be listed in accordance with ANSI Z21.86/CSA 2.32. [NFPA 54:10.25.1]
907.2 Installation. Wall furnaces shall be installed in accor dance with the manufacturer’s installation instructions. Wall
furnaces installed in or attached to combustible material shall be listed for such installation. [NFPA 54:10.25.2.1]
907.2.1 Vented Wall Furnaces. Vented wall furnaces connected to a Type B-W gas vent system listed only for a single story shall be installed only in single-story buildings or the top story of multistory buildings. Vented wall furnaces connected to a Type B-W gas vent system listed for installation in multistory buildings shall be permitted to be installed in single-story or multistory buildings. Type B-W gas vents shall be attached directly to a solid header plate that serves as a firestop at that point and that
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INSTALLATION OF SPECIFIC APPLIANCES
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CMC § 905.8 High relevance — show source text
905.8 Installation in Commercial
Garages and Aircraft Hangars . . . 203
905.9 Electric Duct Heaters . . . . . . . . . . 203
906.0 Floor Furnaces . . . . . . . . . . . . . . . 203
906.1 Application . . . . . . . . . . . . . . . . . . 203
906.2 Installation . . . . . . . . . . . . . . . . . . 204
906.3 Temperature Limit Controls . . . . . 204
906.4 Combustion and Circulating Air. . . 204
906.5 Placement. . . . . . . . . . . . . . . . . . . 204
906.6 Bracing . . . . . . . . . . . . . . . . . . . . . 204
906.7 Support . . . . . . . . . . . . . . . . . . . . . 204
906.8 Clearance . . . . . . . . . . . . . . . . . . . 204
906.9 Access . . . . . . . . . . . . . . . . . . . . . 204
906.10 Seepage Pan . . . . . . . . . . . . . . . . 204
906.11 Wind Protection . . . . . . . . . . . . . . 204
906.12 Upper Floor Installations. . . . . . . . 204
906.13 First Floor Installation . . . . . . . . . . 204
906.14 Oil-Fired Floor Furnaces. . . . . . . . 204
xxxv
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TABLE OF CONTENTS
907.0 Wall Furnaces. . . . . . . . . . . . . . . . 204
907.1 Application . . . . . . . . . . . . . . . . . . 204
907.2 Installation . . . . . . . . . . . . . . . . . . 204
907.3 Location . . . . . . . . . . . . . . . . . . . . 205
907.4 Combustion and Circulating Air . . 205
907.5 Oil-Fired Wall Furnaces . . . . . . . . 205
908.0 Clothes Dryers . . . . . . . . . . . . . . . 205
908.1 Application . . . . . . . . . . . . . . . . . . 205
908.2 Electric Clothes Dryers . . . . . . . . . 205
908.3 Gas-Fired Clothes Dryers. . . . . . . 205
909.0 Conversion Burners . . . . . . . . . . . 205
909.1 General. . . . . . . . . . . . . . . . . . . . . 205
910.0 Burner Assemblies . . . . . . . . . . . . 206
910.1 Oil Burners . . . . . . . . . . . . . . . . . . 206
910.2 Gas Burners . . . . . . . . . . . . . . . . . 206
911.0 Decorative Appliances for Installation in Vented Fireplaces. . . 206
CMC § 140.9 High relevance — show source text
9(c)3B Fume Hood Intensive Laboratories 140.9(c)4, Table 140.9-D Function 110.2(a)3, 110.9(b)1D, 110.12(a), 110.12(c)1, 120.8(b)3, 120.8(f)4, 130.1(c)6D, 130.1(f), 141.0(b)2I, 160.5(b)4C, 160.5(b)4F, 180.3(b)4B Function Areas 120.6(g)1, 120.8, 130.1(c)1C, 130.1(c)3B, 130.1(c), 140.6(a)3D, 140.6(c)2AB, 140.6(c)2G, 140.6(c)3A, 140.6(c)3F, 140.6(c)3, 170.2(e)4 Functional Areas 160.5, 130.0(b) Functional Performance Testing 120.8(a)6, 120.8(g) Furnace Installation 150.0(h)4A, 160.3(b)4A Furnace Output 150.0(h)1 Future 240V Use 150.0(n)1, 150.0(t)2, 150.0(u)2, 150.0(v)2, 160.4(a)1B, 160.9(a)2, 160.9(b)2, 160.9(c)
G
Gas Bypass 140.4(e)3B, 170.2(c)4C Cooler efficiency 120.6(a)8H, 120.6(b)5H Cooler pressure 120.6(a)8E-F, 120.6(b)5E-F Fired furnace 110.2(d), Table 110.2-I, Table 110.2-J Furnace 150.0(m)13, 150.1(c)10, 160.3(b)5L, 170.2(c)3B Heater 110.4(b)2 Log 150.0(e), 160.1(f) Or propane 100.2, 150.0(n)1, 150.0(t-v), 150.1(c)8, 150.2(a)1D, 150.2(b)1H, 160.4(a), 160.9, 170.2(d)1C, 170.2(d)3, 180.2(b)3C Service water heating 140.5(c), 141.0(a)2, 170.2(d)3A Supply 160.4(a)4 Water heater 140.5(c), 150.0(n), 170.2(d)3 Gas- and Oil-fired Boilers, Minimum Efficiency Requirements Table 110.2-J Gasket 110.7, 120.1(c)1D, 150.0(a)3, 150.0(k)1C, 150.0(m)12B, 160.1(a)1B, 160.2(b)1B, 160.2(c)1D, 160.5(a)1C Geometry 140.3(a)6E, 141.0(b)3D2, 150.
CMC § 907.2.3 High relevance — show source text
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]
2025 CALIFORNIA MECHANICAL CODE 205
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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.
911.1 Application. Decorative appliances for installation in vented fireplaces shall be listed in accordance with ANSI Z21.60/CSA 2.26. [NFPA 54:10.6.1]
911.2 Prohibited Installations. Decorative appliances for installation in vented fireplaces shall not be installed in bathrooms or bedrooms unless the bedroom or bathroom has the
required volume in accordance with Section 701.4. [NFPA 54:10.6.2] [OSHPD 1, 1R, 2, 4 & 5] A vented decorative appliance shall not be located in any hospital, skilled nursing facility, intermediate care facility, or correctional treatment
center.
911.3 Installation. A decorative appliance for installation in a vented fireplace shall be installed only in a vented fireplace having a working chimney flue and constructed of noncombustible materials. These appliances shall not be thermostatically controlled. [NFPA 54:10.6.3]
911.3.1 Listed Decorative Appliance. A listed decorative appliance for installation in a vented fireplace shall be installed in accordance with its listing and the manufacturer’s installation instructions. {NFPA 54:10.6.3.1}
911.3.2 Reserved
911.4 Fireplace Screens. A fireplace screen shall be installed with a decorative appliance for installation in a vented fireplace. [NFPA 54:10.6.4]
912.0 Gas Fireplaces, Vented.
912.1 Application. Vented gas fireplaces shall be listed in accordance with ANSI Z21.50/CSA 2.22. [NFPA 54:10.7.1]
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]
2025 CALIFORNIA MECHANICAL CODE 205
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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 § 9-3 Medium relevance — show source text
902 Special Use and Occupancy. . . . . . . . . . . . . . . . . . . . . . 9-3
903 Building Elements and Materials . . . . . . . . . . . . . . . . . 9-3
904 Fire Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4
905 Means of Egress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4
906 Structural. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4
907 Energy Conservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4
908 Emergency Responder Communications Enhancement System Coverage. . . . . . . . . . . . . . . . 9-5
CHAPTER 10 CHANGE OF OCCUPANCY . . . . . . . . . . . . . . .10-3
1001 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
1002 Special Use and Occupancy. . . . . . . . . . . . . . . . . . . . . 10-3
1003 Building Elements and Materials . . . . . . . . . . . . . . . . 10-3
1004 Fire Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
1005 Means of Egress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
1006 Structural. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
1007 Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4
1008 Mechanical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4
1009 Plumbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4
1010 Other Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5
1011 Change of Occupancy Classification . . . . . . . . . . . . . 10-5
CHAPTER 11 ADDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . .11-3
CMC § 4.6 Medium relevance — show source text
(b) Vertical half-scale wall furnace. The furnace exposure panel or door shall consist of an insulated steel restraining frame having an available opening of not less than 50 square feet (4.6 m [2] ) for the test sample. Neither dimension of the furnace opening shall be less than 7 feet (2133 mm).
(c) Horizontal large-scale floor furnace. The furnace exposure panel shall consist of an insulated steel restraining frame having an available opening of not less than 180 square feet (16.7 m [2] ) for the test sample. Neither dimension of the furnace opening shall be less than 12 feet (3657 mm).
(d) Horizontal small-scale furnace. The furnace exposure panel shall consist of an insulated frame having an available opening of not less than 35 square feet (3 m [2] ) for the test sample. Neither dimension of the furnace opening shall be less than 5 feet (1524 mm).
(e) Horizontal large-scale beam furnace. The furnace exposure panel shall consist of an insulated steel restraining frame having an available opening of not less than 180 square feet (16.7 m [2] ) for the test sample. Neither dimension of the furnace opening shall be less than 5 feet (1524 mm).
(f) Horizontal small-scale beam furnace. The furnace exposure panel for the “Alternate Test of Protection for Structural Steel Beams, Girders and Trusses” shall consist of an insulated steel frame having an available opening of not less than 35 square feet (3 m [2] ) for the test sample. Neither dimension of the furnace opening shall be less than 5 feet (1524 mm).
(g) Column furnace. The column furnace shall be of such dimensions as to provide an opening for column sections not less than 8 feet (2438 mm) in clear length.
(h) Protection of equipment and test specimen. The testing furnaces, equipment and test specimen undergoing the fire test shall be protected from any condition of wind or weather, that might lead to abnormal results. The ambient air temperature of the testing room at the beginning of the test shall be within the range of 50°F to 90°F (10°C to 32°C). Velocity of air across the unexposed face of the test specimen shall not exceed 4.4 feet per second, as determined by an anemometer placed at right angles to the unexposed surface, measured before or during the test. If mechanical ventilation is employed during the test, an airstream shall not be directed across the surface of the specimen.
BURNERS AND FUEL
Sec. 12-7-302.
(a) Burners.
- In vertical furnaces, burners shall be placed in the back wall of the furnace. The location of the burners and provisions for combustion air shall be such as to provide an even flame exposure to the entire exposed face of the test specimen. Combustion air openings shall be provided in such a manner as to normally prevent induction of combustion air through any opening in the test specimen.
- In horizontal furnaces, burners shall be placed in the floor or side walls. Burrs and the provisions for combustion air shall be so arranged as to provide a uniform exposure to the entire exposed face of the test specimen.
- In column furnaces, burners shall be placed in the four walls to provide an even luminous flame exposure to all sides of the test sample.
(b) Fuel. Furnaces shall be supplied with natural, manufactured or bottled gas.
2025 CALIFORNIA REFERENCED STANDARDS CODE 25
CMC § 304.3.1.1 Medium relevance — show source text
304.3.1.1 Access Type. The inside means of access shall be a permanent or foldaway inside stairway or ladder, terminating in an enclosure, scuttle, or trapdoor. Such scuttles or trapdoors shall be at least 22 inches by 24 inches (559 mm by 610 mm) in size, shall open easily and safely under all conditions, especially snow, and shall be constructed so as to permit access from the roof side unless deliberately locked on the inside.
At least 6 feet (1829 mm) of clearance shall be available between the access opening and the edge of the roof or similar hazard, or rigidly fixed rails or guards a minimum of 42 inches (1067 mm) in height shall be provided on the exposed side. Where parapets or other building structures are utilized in lieu of guards or rails, they shall be a minimum of 42 inches (1067 mm) in height. [NFPA 54:9.4.3.3]
304.3.1.2 Permanent Ladders. Permanent lad ders required by Section 304.3.1.1 shall be constructed in accordance with the following:
(1) Side railings shall extend not less than 30 inches (762 mm) above the roof or parapet wall.
(2) Landings shall not exceed 18 feet (5486 mm) apart measured from the finished grade.
(3) Width shall be not less than 14 inches (356 mm)
on center.
(4) Rungs spacing shall not exceed 12 inches (305 mm) on center, and each rung shall be capable of supporting a 300 pound (136.1 kg) load.
(5) Toe space shall be not less than 6 inches (152 mm).
304.3.2 Permanent Lighting. Permanent lighting shall be provided at the roof access. The switch for such lighting shall be located inside the building near the access means leading to the roof. [NFPA 54:9.4.3.4]
304.4 Appliances in Attics and Under-Floor Spaces. An attic or under-floor space in which an appliance is installed shall be accessible through an opening and passageway larger than the largest component of the appliance, and not less than 22 inches by 30 inches (559 mm by 762 mm). {NFPA 54:9.5.1}
304.4.1 Length of Passageway. Where the height of the passageway is less than 6 feet (1829 mm), the distance from the passageway access to the appliance shall not exceed 20 feet (6096 mm) measured along the centerline of the passageway. [NFPA 54:9.5.1.1] Where the height of the passageway is 6 feet (1829 mm) or more, the distance from the passageway access to the appliance shall not exceed 50 feet (15 240 mm) measured along the centerline of the passageway.
304.4.2 Width of Passageway. The passageway shall be unobstructed and shall have solid flooring not less than 24 inches (610 mm) wide from the entrance opening to the appliance. [NFPA 54:9.5.1.2]
54 2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
GENERAL REGULATIONS
CMC § 1.1.6 Medium relevance — show source text
Notes:
Tested at NBS under ASA Spec. No. A2-1934.
One unit in wall thickness.
Two units in wall thickness.
Two or three units in wall thickness.
Two cells in wall thickness.
Three or four cells in wall thickness.
Four or five cells in wall thickness.
Five or six cells in wall thickness.
Minimum percent of solid materials in units = 40%.
Minimum percent of solid materials in units = 43%.
Minimum percent of solid materials in units = 46%.
Minimum percent of solid materials in units = 48%.
Minimum percent of solid materials in units = 49%.
Minimum percent of solid materials in units = 45%.
Minimum percent of solid materials in units = 51%.
Minimum percent of solid materials in units = 53%.
Not less than [5] / 8 inch thickness of 1:3 sanded gypsum plaster.
Noncombustible or no members framed into wall.
Combustible members framed into wall.
Load: 80 psi for gross area.
Portland cement-lime mortar.
Failure mode–thermal.
British test.
Passed all criteria.
Failed by sudden collapse with no preceding signs of impending failure.
One cell in wall thickness.
Two cells in wall thickness.
Three cells in wall thickness.
Minimum percent of solid material in concrete units = 52%.
Minimum percent of solid material in concrete units = 54%.
Minimum percent of solid material in concrete units = 55%.
Minimum percent of solid material in concrete units = 57%.
Minimum percent of solid material in concrete units = 60%.
Minimum percent of solid material in concrete units = 62%.
Minimum percent of solid material in concrete units = 65%.
Minimum percent of solid material in concrete units = 70%.
Minimum percent of solid material in concrete units = 76%.
Not less than [1] / 2 inch of 1:3 sanded gypsum plaster.
Three units in wall thickness.
Concrete units made with expanded slag or pumice aggregates.
Concrete units made with expanded burned clay or shale, crushed limestone, air-cooled slag or cinders.
2025 CALIFORNIA EXISTING BUILDING CODE RESOURCE A-47
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
RESOURCE A—GUIDELINES ON FIRE RATINGS OF ARCHAIC MATERIALS AND ASSEMBLIES
TABLE 1.1.6—continued
MASONRY WALLS 12 ″ TO LESS THAN 14 ″ THICK
- Concrete units made with calcareous sand and gravel. Coarse aggregate, 60 percent or more calcite and dolomite.
- Concrete units made with siliceous sand and gravel. Ninety percent or more quartz, chert or flint.
- Load: 160 psi of gross wall cross-sectional area.
- Load: 120 psi of gross wall cross-sectional area.
FIGURE 1.1.7
MASONRY WALLS
14 ″ OR MORE THICK
NUMBER OF ASSEMBLIES
10
5
0
CMC § 10.7.3 Medium relevance — show source text
(1) [HCD 1 & HCD 2] Any newly installed gas fireplace shall be a direct-vent sealed-combustion type.
(2) Vented gas fireplaces shall be installed in accordance with their listing and the manufacturer’s installation instructions and where installed in or attached to com bustible material shall be specifically listed for such installation.
(3) Panels, grilles, and access doors that are required to be removed for normal servicing operations shall not be attached to the building.
(4) Direct vent gas fireplaces shall be installed with the vent air intake terminal in the outdoors and in accor dance with the manufacturer’s installation instructions.
[NFPA 54:10.7.3] 912.4 Combustion and Circulating Air. Combustion and circulating air shall be provided in accordance with Section 701.0. [NFPA 54:10.7.4]
913.0 Factory-Built Fireplaces and Fireplace Stoves. 913.1 Factory-Built Fireplaces. Factory-built fireplaces shall comply with UL 127 and installed in accordance with the manufacturer’s installation instructions. {NFPA 211:11.1.1} 913.1.1 Gasketed Fireplace Doors. A gasketed fireplace door shall not be installed on a factory-built fireplace, except where the fireplace system has been tested in accordance with UL 127.
913.2 Fireplace Stoves. Fireplace stoves shall comply with UL 737 and installed in accordance with the manufac turer’s installation instructions.
913.3 Fireplace Accessories. Heat exchangers, glass doors assemblies, combustion air vents, and termination caps shall comply with UL 907 and installed in accordance with the manufacturer’s installation instructions.
914.0 Non-Recirculating Direct Gas-Fired Industrial Air Heaters.
914.1 Application. Direct gas-fired heating and forced ventilation appliances for commercial and industrial applications shall be listed in accordance with the following standards as applicable:
(1) ANSI Z83.4/CSA 3.7.
(2) ANSI Z83.18. [NFPA 54:10.8.1] 914.2 Prohibited Installations. Direct gas-fired heating and forced ventilation appliances shall not serve any area containing sleeping quarters. Non-recirculating direct gas-fired heating and forced ventilation appliances shall not recirculate room air.
Recirculating direct gas-fired industrial air heaters shall not recirculate room air in buildings that contain flammable solids, liquids, or gases; explosive materials; or substances that can become toxic when exposed to flame or heat. [NFPA 54:10.8.2.1 – 10.8.2.3]
914.3 Installation. Direct gas-fired heating and forced ventilation appliances shall be installed in accordance with the manufacturer’s instructions. [NFPA 54:10.8.3.1]
914.3.1 Fresh Air Ventilation. Direct gas-fired heating and forced ventilation appliances shall be permitted to provide fresh air ventilation. [NFPA 54:10.8.3.2]
914.3.2 Access Required. Direct gas-fired heating and forced ventilation appliances shall be provided with access for removal of burners; for replacement of motors, controls, filters, and other working parts; and for adjustment and lubrication of parts requiring maintenance.
[NFPA 54:10.8.3.3]
206 2025 CALIFORNIA MECHANICAL CODE
Frequently asked questions
Can I install an unlisted wall furnace in a combustible wall?
No. Wall furnaces installed in or attached to combustible material must be specifically listed for such installation; otherwise the installation is not permitted. See § 907.2.
What does “direct vent” mean for a wall furnace?
A direct‑vent wall furnace must have its combustion‑air intake located outdoors (combustion air terminal outdoors). See § 907.2.2.
My unit’s Type B‑W vent is labeled “single‑story only.” Where can I install it?
A Type B‑W vent listed only for single‑story use may be used only in a single‑story building or in the top story of a multistory building — it cannot be installed in lower stories of a multistory building. See § 907.2.1.
Do I have to follow the manufacturer’s instructions?
Yes — § 907.2 requires installation in accordance with the manufacturer’s installation instructions, and listed appliances must be installed per their listing.
Where do I find how much combustion air I must provide?
Section § 907.4 requires combustion and circulating air be provided per § 701.0; for the quantitative requirements (opening sizes, indoor volume thresholds, outdoor/indoor combinations, engineered or mechanical supply) consult § 701.0 directly.
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