CMC · California Mechanical Code

What clearances to combustible materials are required for appliances?

Appliances and their vent connectors must be installed with clearances so they cannot ignite nearby combustibles. The CMC’s general rule is in **§303.10**: use the specific clearance numbers in the appliance chapters or the appliance’s listing/manufacturer instructions; reduced clearances are allowed only per **§303.10.1** and **Table 303.10.1**. For example, solid‑fuel appliances default to **12 in** to walls and **18 in** to ceilings unless the listing says otherwise (**§303.10.1.3**) .

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Last reviewed: July 6, 2026

What the code requires — plain English

Appliances and their vent connectors must be installed with sufficient clearance from combustible material so their operation does not create a hazard — that is the core rule in §303.10. Where the Code provides minimum clearances, those values appear in the appliance-specific chapters (Chapters 8 and 9) or NFPA 211; where the Code does not provide values, you must follow the appliance listing and the manufacturer’s instructions (see §303.10, §303.1, and §303.3) . Reduced clearances are allowed only where permitted by the appliance listing or by Table 303.10.1 and related sub‑sections (see §303.10.1) .

The single most important rule: install appliances and vent connectors so they cannot ignite nearby combustibles — follow the specific clearance numbers in the Code chapters or the appliance listing/manufacturer; otherwise use the reduction rules in §303.10.1.

Requirements in detail

The general rule (where to look)

  • The Code requires clearances so operation does not create a hazard (§303.10) and points you to appliance‑specific minimums in Chapters 8 and 9 or NFPA 211; if a clearance is not provided in the Code, use the appliance listing and the manufacturer’s installation instructions (§303.10, §303.1, §303.3) .
  • Reduced clearances for listed equipment must follow the listing and Table 303.10.1; for unlisted equipment, reduced clearances are permitted only where the manufacturer allows and Table 303.10.1 is followed (§303.10.1) .

Key appliance-specific values (decision‑relevant)

The Code contains many appliance‑specific clearance rules in later chapters. Below are commonly used, decision‑relevant values that the CMC states explicitly. Always confirm on the appliance nameplate/listing and manufacturer instructions in addition to these sections.

Situation / Measurement decision Required clearance (CMC) Code Reference
Solid‑fuel‑burning appliance — clearance to combustible walls Not less than 12 inches (305 mm) §303.10.1.3
Solid‑fuel‑burning appliance — clearance to combustible ceilings Not less than 18 inches (457 mm) §303.10.1.3
Unit heaters — sides (listed unless otherwise allowed) Not less than 18 inches (457 mm) §916.3 / unit heater rules
Unit heaters — bottom Not less than 12 inches (305 mm) §916.3 / unit heater rules
Unit heaters — top (internal draft hood) Not less than 6 inches (152 mm); vertical draft hood 1 inch (25.4 mm) at sloping side §916.3 / unit heater rules
Food‑service counter appliances — vertical clearance above hot plates/griddles Not less than 48 inches (1219 mm) §918.2
Floor‑mounted food‑service appliances (horizontal clearance from combustibles) Not less than 6 inches (152 mm) (2 inches between draft hood and combustibles) §917.2
Duct furnaces (listed) — clearance to adjacent combustible walls/ceilings/floors Not less than 6 inches (152 mm) §905.2(1)
Central heating furnace — clearance from supply ducts (first 3 ft / next 3 ft / beyond 6 ft) 18 in / 6 in / 1 in respectively (see full formula in §904.3.7) §904.3.7
Refrigerator ventilation (if no manufacturer instruction available) — back / top At least 2 inches (51 mm) at back and 12 inches (305 mm) above top §927.2
Working/service space (general for appliances) Not less than 30 inches (762 mm) depth/width/height unless otherwise specified §304.1

Notes:

  • The table above is a selection — the Code lists many other appliance‑specific clearances in Chapters 8 and 9; where a specific appliance chapter gives a required clearance, that value controls (see §303.10) .
  • Where an appliance is listed for lesser clearances, the listing and manufacturer instructions control (see §303.1 and §303.10.1) .

Clearance reductions and protection

  • Table 303.10.1 in the Code provides the framework for allowable reduced clearances and describes protective methods (see §303.10.1) .
  • Certain systems have special reduction rules: Type I hood exhaust systems and product‑conveying ducts have their own reduction requirements referenced in §303.10.1.1 and §303.10.1.2 — reductions are only allowed per those sections and related hood/duct provisions .
  • If the appliance is unlisted and the manufacturer permits reduced clearances, the Code allows use of Table 303.10.1 where not otherwise provided in the Code — otherwise you need AHJ approval (§303.10.1) .

Exceptions & special cases

  • Appliances that are listed for reduced clearances are permitted to be installed at those reduced clearances per their listing and instructions — do not reduce below what the listing allows (§303.10.1, §303.1) .
  • Solid‑fuel‑burning appliances have an explicit minimum if not otherwise listed: 12 in to walls and 18 in to ceilings; nevertheless, listed solid‑fuel appliances with lesser clearances may be installed per their listing (§303.10.1.3) .
  • Type I hood exhaust systems and product‑conveying ducts are regulated by other specific sections and have separate reduction constraints — reductions must follow those sections (§507.4.2 series, §506.10.3 series as referenced in §303.10.1.1/§303.10.1.2) .
  • For appliances installed on combustible floors, the Code either requires the appliance be listed for that condition or the combustible floor be protected in an approved manner (see appliance‑specific sections such as §904.4 for furnaces and §917.3 for food‑service appliances) .

Common mistakes

  • Treating a single Code table as universal: many appliances have their own clearance rules in Chapters 8 and 9 — always check the appliance chapter and the appliance listing (see §303.10) .
  • Reducing clearances without referencing Table 303.10.1, the appliance listing, or the manufacturer’s instructions — reductions must be explicitly allowed by those sources (§303.10.1) .
  • Confusing service/access clearances (e.g., §304.1 — 30 in working space) with clearances to combustible materials — they are separate requirements and both must be met where applicable .
  • Ignoring nameplate/listing data — the Code requires listed appliances to be installed per their listing and nameplate clearances (§303.1) .
  • Installing unlisted appliances without AHJ approval or without following manufacturer instructions and the Code’s clearance rules (§303.3) .

Worked example — concrete scenario

Scenario: you are installing a freestanding, unlisted solid‑fuel stove in a living room with combustible walls and ceiling. The stove manufacturer instructions are not available on site.

  1. Start with the Code default for solid fuel appliances: maintain at least 12 inches to combustible walls and 18 inches to combustible ceilings per §303.10.1.3 .
  2. If the stove is later found to be listed for reduced clearances (for example, the listing allows 6 inches to a wall), you may install at the listed clearance but only in accordance with the listing and the manufacturer’s instructions (§303.10.1.3, §303.1) .
  3. If you wish to reduce clearances for an unlisted stove, you must have the manufacturer permit the reduction and comply with Table 303.10.1 (or obtain AHJ approval) — do not assume you can arbitrarily reduce clearances (§303.10.1) .
  4. Finally, ensure service clearances (e.g., access and working space) are met — general working space is 30 inches unless otherwise specified (§304.1) .

Related provisions (quick list)

  • §303.10 — Clearance to combustible materials (primary control)
  • §303.10.1 — Clearance reduction rules and Table 303.10.1
  • §303.10.1.1 — Type I hood exhaust system reduction rules (see hood chapters)
  • §303.10.1.3 — Solid‑fuel‑burning appliance minimums (12 in / 18 in)
  • §303.1 — Listed appliances: follow listing and nameplate clearances
  • §303.3 — Unlisted appliances: AHJ approval and instructions required
  • §304.1 — Accessibility and 30‑inch working space requirement
  • §904.3.3 — Reduced clearances for furnaces/boilers and reference to Table 303.10.1
  • §905.2 — Duct furnace clearances (listed units)
  • §916.3 / §916.4 — Unit heater clearances and combustion air rules
  • §918.2 — Vertical clearance for food‑service hot plates and griddles
  • §927.2 — Refrigerator ventilation clearances when manufacturer info is not available

Code references

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

  • CMC § 303.10.1.3 High relevance — show source text

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    303.10.1.3 Solid-Fuel-Burning Appliances. For solid-fuel-burning appliances, the clearance shall not be less than 12 inches (305 mm) to combustible walls and not less than 18 inches (457 mm) to combustible ceilings. The clearance, after reduction, shall be permitted to be less than 12 inches (305 mm) to combustible walls and less than 18 inches (457 mm) to combustible ceilings. Solid-fuel-burning appliances listed for lesser clearances shall be permitted to be installed in accordance with the manufacturer’s instructions and their listing. 303.11 Installation in Commercial Garages. Appliances installed in commercial garages shall be in accordance with Section 303.11.1 through Section 303.11.2. 303.11.1 Parking Structures. Appliances installed in enclosed, basement, and underground parking structures shall be installed in accordance with NFPA 88A. [NFPA 54:9.1.11.1] 303.11.2 Repair Garages. Appliances installed in repair garages shall be installed in accordance with NFPA 30A. [NFPA 54:9.1.11.2]

    303.12 Installation in Aircraft Hangars. Heaters in aircraft hangars shall be installed in accordance with NFPA 409.

    [NFPA 54:9.1.12]

    304.0 Accessibility for Service. 304.1 General. All appliances shall be located with respect to building construction and other equipment so as to permit access for repair or replacement of the appliance. Clearance shall be maintained to permit removal of the appliance; cleaning of heating surfaces; the replacement of filters, blowers, motors, burners, controls, and vent connections; the lubrication of moving parts where necessary; the adjustment and cleaning of burners and pilots; and the proper functioning of explosion vents, if provided. For attic installation, the passageway and servicing area adjacent to the appliance shall be in accordance with Section 304.4. {NFPA 54:9.2.1}

    Unless otherwise specified, clearances of not less than 30 inches (762 mm) in depth, width, and height of working space shall be maintained.

    Exception: A platform shall not be required for unit heaters or room heaters.

    304.2 Sloped Roof. Where equipment or appliances that require service are installed on a roof having a slope of 4 units vertical in 12 units horizontal (33 percent slope) or more, a level platform of not less than 30 inches by 30 inches (762 mm by 762 mm) shall be provided at the service side of the equipment or appliance. 304.3 Access to Appliances on Roofs. Appliances located on roofs or other elevated locations shall be accessible. [NFPA 54:9.4.3.1]

    304.3.1 Access from the Inside. Buildings of more than 15 feet (4572 mm) in height shall have an inside means of access to the roof unless other means acceptable to the Authority Having Jurisdiction are used. [NFPA 54:9.4.3.2]

  • CMC § 303.8.5 High relevance — show source text

    (1) The clearance between the appliance and a roof edge or open end of an equipment platform is less than 6 feet (1829 mm).

    (2) The open end of the equipment platform is located more than 30 inches (762 mm) above the roof, floor, or grade below.

    Where guards or rails are installed, they shall be constructed so as to prevent the passage of a 21 inch (533 mm) diameter ball, resist the imposed loading conditions, and shall extend not less than 30 inches (762 mm) beyond each side of the equipment or appliance.

    Exception: Guards shall not be required where a permanent fall arrest anchorage connector system in accordance with ASSP Z359.1 is installed.

    303.8.5 Electrical Power. Appliances requiring an external source of electrical power shall be installed in accordance with the California Electrical Code . [NFPA 54:9.4.2.3]

    303.8.6 Platform or Walkway. Where water stands on the roof at the appliance or in the passageways to the appliance, or where the roof is of a design having a water seal, a suitable platform, walkway, or both shall be provided above the water line. Such platform(s) or walkway(s) shall be located adjacent to the appliance and control panels so that the appliance can be safely serviced where water stands on the roof. [NFPA 54:9.4.2.4] 303.9 Avoiding Strain on Gas Piping. Appliances shall be supported and connected to the piping so as not to exert undue strain on the connections. [NFPA 54:9.1.16] 303.10 Clearance to Combustible Materials. Appliances and their vent connectors shall be installed with clearances from combustible material so their operation does not create a hazard to persons or property. Minimum clearances between combustible walls and the back and sides of various conventional types of appliances and their vent connectors are specified in Chapter 8 and Chapter 9, or NFPA 211.

    [NFPA 54:9.2.2] Where not provided in this code, listed and unlisted equipment or appliances shall be installed to maintain the required clearances for servicing and to combustible construction in accordance with the listing and the manufacturer’s installation instructions.

    303.10.1 Clearance Reduction. Reduced clearances to combustible construction for listed equipment and appliances shall comply with the listing and Table 303.10.1. Where permitted by the manufacturer, and not provided in this code, reduced clearances to combustible construction for unlisted equipment and appliances shall comply with Table 303.10.1. 303.10.1.1 Type I Hood Exhaust System. Reduced clearances for Type I exhaust systems shall be in accordance with Section 507.4.2 through Section 507.4.2.3. Clearances from the duct or the

    exhaust fan to the interior surface of enclosures of

    combustible construction shall be in accordance with

    Section 510.7.3 and clearances shall not be reduced.

    303.10.1.2 Product Conveying Ducts. Reduced clearances to combustibles construction for product conveying ducts shall be in accordance with Section 506.10.3 through Section 506.11.6.3.

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  • CMC § 9.2.2 High relevance — show source text

    ** Appliances and their vent connectors shall be installed with clearances from combustible material so their operation does not create a hazard to persons or property. Minimum clearances between combustible walls and the back and sides of various conventional types of appliances and their vent connectors are specified in Chapter 8 and Chapter 9, or NFPA 211.

    [NFPA 54:9.2.2] Where not provided in this code, listed and unlisted equipment or appliances shall be installed to maintain the required clearances for servicing and to combustible construction in accordance with the listing and the manufacturer’s installation instructions.

    303.10.1 Clearance Reduction. Reduced clearances to combustible construction for listed equipment and appliances shall comply with the listing and Table 303.10.1. Where permitted by the manufacturer, and not provided in this code, reduced clearances to combustible construction for unlisted equipment and appliances shall comply with Table 303.10.1. 303.10.1.1 Type I Hood Exhaust System. Reduced clearances for Type I exhaust systems shall be in accordance with Section 507.4.2 through Section 507.4.2.3. Clearances from the duct or the

    exhaust fan to the interior surface of enclosures of

    combustible construction shall be in accordance with

    Section 510.7.3 and clearances shall not be reduced.

    303.10.1.2 Product Conveying Ducts. Reduced clearances to combustibles construction for product conveying ducts shall be in accordance with Section 506.10.3 through Section 506.11.6.3.

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    303.10.1.3 Solid-Fuel-Burning Appliances. For solid-fuel-burning appliances, the clearance shall not be less than 12 inches (305 mm) to combustible walls and not less than 18 inches (457 mm) to combustible ceilings. The clearance, after reduction, shall be permitted to be less than 12 inches (305 mm) to combustible walls and less than 18 inches (457 mm) to combustible ceilings. Solid-fuel-burning appliances listed for lesser clearances shall be permitted to be installed in accordance with the manufacturer’s instructions and their listing. 303.11 Installation in Commercial Garages. Appliances installed in commercial garages shall be in accordance with Section 303.11.1 through Section 303.11.2. 303.11.1 Parking Structures. Appliances installed in enclosed, basement, and underground parking structures shall be installed in accordance with NFPA 88A. [NFPA 54:9.1.11.1] 303.11.2 Repair Garages. Appliances installed in repair garages shall be installed in accordance with NFPA 30A. [NFPA 54:9.1.11.2]

    303.12 Installation in Aircraft Hangars. Heaters in aircraft hangars shall be installed in accordance with NFPA 409.

    [NFPA 54:9.1.12]

  • CMC § 302.3.2 High relevance — show source text

    302.3.2 Technical Data. The registered design professional shall submit sufficient technical data to substantiate the proposed alternative engineered design and to prove that the performance meets the intent of this code.

    302.3.3 Design Documents. The registered design professional shall provide two complete sets of signed and sealed design documents for the alternative engineered design for submittal to the Authority Having Jurisdiction. The design documents shall include floor plans of the work. Where appropriate, the design documents shall indicate location, sizing, and loading of appurtenances, equipment, appliances, and devices.

    302.3.4 Design Approval. An approval of an alternative engineered design shall be at the discretion of the Authority Having Jurisdiction. The exercise of this discretionary approval by the Authority Having Jurisdiction shall have no effect beyond the jurisdictional boundaries of said Authority Having Jurisdiction. An alternative engineered design so approved shall not be considered as in accordance with the requirements, intent, or both of this code for a purpose other than that granted by the Authority Having Jurisdiction.

    302.3.5 Design Review. The Authority Having Jurisdiction shall have the authority to require testing of the alternative engineered design in accordance with Section 302.2.1, including the authority to require an independent review of the design documents by a registered design professional selected by the Authority Having Jurisdiction and at the expense of the applicant.

    302.3.6 Inspection and Testing. The alternative engineered design shall be tested and inspected in accordance with the submitted testing and inspection plan and the requirements of this code.

    303.0 Installation.

    303.1 Listed Appliances. The installation of equipment and appliances regulated by this code shall be in accordance with the conditions of the listing, the manufacturer’s installation instructions and this code. The manufacturer’s instal lation and operating instructions shall be attached to the appliance. Clearances of listed equipment and appliances from combustible materials shall be as specified in the listing or on the rating plate.

    303.2 Closet or Alcove Installations. [Not adopted for OSHPD 1, 1R, 2, 3, 4 & 5] Central heating furnaces and boilers installed in closets or alcoves shall be listed for such

    installation. Central heating furnaces not listed for closet or alcove installation shall be installed in a room or space having a volume not less than 12 times the total volume of the furnace. Central heating boilers not listed for closet or alcove installation shall be installed in a room or space having a volume 16 times the volume of the boiler. Where the ceiling height of the room or space exceeds 8 feet (2438 mm), the volume shall be calculated on the basis of an 8 foot (2438 mm) height.

    The installation clearances shall be in accordance with

    the appliance listing, shall not be reduced, and shall be installed in accordance with Section 904.3.

    303.3 Unlisted Appliances. Except as otherwise permitted in this code, unlisted equipment and appliances shall be approved by the Authority Having Jurisdiction prior to being installed. Unlisted equipment and appliances shall be installed in accordance with the manufacturer’s installation instruc tions and with clearances from combustible materials in

    accordance with Section 303.10 or Section 303.10.1.

    303.4 Anchorage of Appliances. Appliances designed to be fixed in position shall be securely fastened in place in

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  • CMC § 903.2.2 High relevance — show source text

    903.2.2 Independent Gas Piping. Gas piping serving heating appliances shall be permitted to also serve cooling appliances where heating and cooling appliances cannot be operated simultaneously. [NFPA 54:10.2.2]

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    INSTALLATION OF SPECIFIC APPLIANCES

    904.3.3 Listed and Unlisted Units. Central heating furnaces and low-pressure boilers shall be permitted to be installed with reduced clearances to combustible material, provided that the combustible material or appliance is protected as described in Table 303.10.1 and Figure 303.10.1(1) through Figure 303.10.1(3), and such reduction is allowed by the manufacturer’s installation instructions. [NFPA 54:10.3.3.3]

    904.3.4 Front Clearance. Front clearance shall be sufficient for servicing the burner and the furnace or boiler.

    [NFPA 54:10.3.3.4]

    904.3.5 Adjacent to Plaster or Noncombustible Materials. Where the furnace plenum is adjacent to plaster on metal lath or noncombustible material attached to combustible material, the clearance shall be measured to the surface of the plaster or other noncombustible finish where the clearance specified is 2 inches (51 mm) or less. [NFPA 54:10.3.3.5]

    904.3.6 Interference. The clearances to these appliances shall not interfere with combustion air, draft hood clearance and relief, and accessibility for servicing.

    [NFPA 54:10.3.3.6] 904.3.7 Central Heating Furnaces. Central heating furnaces other than those listed in Section 603.13.2 or Section 603.13.3 shall have clearances from the supply ducts of not less than 18 inches (457 mm) from the furnace plenum for the first 3 feet (914 mm), then 6 inches (152 mm) for the next 3 feet (914 mm) and 1 inch (25.4 mm) beyond 6 feet (1829 mm). [NFPA 54:10.3.3.9] 904.4 Assembly and Installation. A central heating boiler or furnace shall be installed in accordance with the manufacturer’s instructions in one of the following manners:

    (1) On a floor of noncombustible construction with noncombustible flooring and surface finish and with no combustible material against the underside thereof.

    (2) On fire-resistive slabs or arches having no combustible material against the underside thereof.

    Exceptions:

    (1) Appliances listed for installation on a combustible floor.

    (2) Installation on a floor protected in an approved manner.

    [NFPA 54:10.3.4]

    904.4.1 Under-Floor Installation. Furnaces installed in an under-floor area of the building shall be in accordance with the Section 904.4.1.1 through Section 904.4.1.3.

    904.4.1.1 Supported by Ground. Where a furnace is supported by the ground, it shall be installed on a concrete slab not less than 3 inches (76 mm) above the adjoining ground level.

  • CMC § 25.4 High relevance — show source text

    (1) Unit heaters shall be installed with clearances from combustible material of not less than 18 inches (457 mm) at the sides, 12 inches (305 mm) at the bottom, and 6 inches (152 mm) above the top where the unit heater has an internal draft hood, or 1 inch (25.4 mm) above the top of the sloping side of a vertical draft hood. A unit heater listed for reduced clearances shall be installed in accordance with its listing and the manufacturer’s installation instructions.

    (2) Clearances for servicing shall be in accordance with the manufacturer’s installation instructions. {NFPA 54:10.24.3}

    916.3.1 Floor-Mounted-Type Unit Heaters. Floormounted-type unit heaters shall comply with the following requirements:

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    permitted where protected in accordance with Table 303.10.1.

    [NFPA 54:10.11.5] 917.6 Use with Casters. Floor-mounted appliances with casters shall be listed for such construction and shall be

    installed in accordance with the manufacturer’s installation instructions for limiting the movement of the appliance to prevent strain on the connection. [NFPA 54:10.11.6]

    917.7 Level Installation. Floor-mounted food service appliances shall be installed level on a firm foundation.

    [NFPA 54:10.11.7]

    917.8 Ventilation. Means shall be provided to properly ventilate the space in which a food service appliance is installed to permit proper combustion of the gas. [NFPA 54:10.11.8]

    918.0 Food Service Appliances, Counter Appliances.

    918.1 Application. Food service counter appliances shall be listed in accordance with ANSI Z83.11/CSA 1.8. [NFPA 54:10.12.1]

    918.2 Vertical Clearance. A vertical distance of not less than 48 inches (1219 mm) shall be provided between the top of all food service hot plates and griddles and combustible material. [NFPA 54:10.12.2]

    918.3 Clearance for Listed Appliances. Listed food service counter appliances such as hot plates and griddles, food and dish warmers, and coffee brewers and urns, where installed on combustible surfaces, shall be set on their own bases or legs and shall be installed with a horizontal clearance of not less than 6 inches (152 mm) from combustible material, except that not less than a 2 inches (51 mm) clearance shall be maintained between a draft hood and combustible material. Food service counter appliances listed for installation at lesser clearances shall be installed in accordance with their listing and the manufacturer’s installation instructions.

    918.4 Clearance for Unlisted Appliances. Food service counter appliances, where installed on combustible surfaces, shall be installed with a minimum horizontal clearance of 6 inches (152 mm) from combustible material, except that at least a 2 inch (51 mm) clearance shall be maintained between a draft hood and combustible material. Food service counter appliances listed for installation at lesser clearances shall be installed in accordance with the manufacturer’s installation instructions. [NFPA 54:10.12.3]

  • CMC § 307.3 High relevance — show source text

    (1) The name or trademark of the manufacturer.

    (2) The model number or equivalent.

    (3) The serial number.

    (4) The electrical rating in volts, amperes (or watts), and, for other than single phase, the number of phases.

    (5) The output rating in Btu/h (kW).

    (6) The electrical rating in volts, amperes, or watts of each field-replaceable electrical component.

    (7) The symbol of an approved agency certifying compliance of equipment with recognized standards.

    (8) Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.

    An appliance shall be accompanied by clear and complete installation instructions, including required clearances from combustibles other than mounting or adjacent surfaces, and temperature rating of field-installed wiring connections exceeding 140°F (60°C). 307.3 Heat Pump and Electric Cooling Appliances. Heat pumps and electric cooling appliances shall bear a permanent and legible factory-applied nameplate on which shall

    appear:

    (1) The name or trademark of the manufacturer.

    (2) The model number or equivalent.

    (3) The serial number.

    (4) The amount of refrigerant.

    (5) The refrigerant designation.

    (6) The factory test pressures or pressures applied.

    (7) The electrical rating in volts, amperes, and, for other than single phase, the number of phases.

    (8) The output rating in Btu/h (kW).

    (9) The electrical rating in volts, amperes, or watts of each field replaceable electrical component.

    (10)The symbol of an approved agency certifying compliance of the equipment with recognized standards.

    (11)Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.

    An appliance shall be accompanied by clear and complete installation instructions, including required clearances from combustible other than mounting or adjacent surfaces, and temperature rating of field-installed wiring connections exceeding 140°F (60°C). 307.4 Absorption Units. Absorption units shall bear a permanent and legible factory-applied nameplate on which shall

    appear:

    (1) The name or trademark of the manufacturer.

    (2) The model number or equivalent.

    (3) The serial number.

    (4) The amount of refrigerant.

    (5) The refrigerant designation.

    (6) Hourly rating in Btu/h (kW).

    (7) The type of fuel approved for use with the unit.

    (8) Cooling capacity Btu/h (kW).

    (9) Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.

    (10)The symbol of an approved agency certifying compliance of the equipment with recognized standards.

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    GENERAL REGULATIONS

    308.0 Improper Location.

    308.1 General. Piping or equipment shall not be so located as to interfere with the normal use thereof or with the normal operation and use of windows, doors, or other required facilities.

    309.0 Workmanship.

    309.1 Engineering Practices. Design, construction, and workmanship shall comply with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this code.

  • CMC § 9.1.18 High relevance — show source text

    (4) In the case of bleed lines entering the combustion chamber, the bleed line shall be located so the bleed gas is readily ignited by the pilot and the heat liberated thereby does not adversely affect the normal operation of the safety shutoff system. The terminus of the bleed line shall be securely held in a fixed position relative to the pilot. For manufactured gas, the need for a flame arrester in the bleed line piping shall be determined.

    (5) A bleed line(s) from a diaphragm-type valve and a vent line(s) from an appliance pressure regulator shall not be connected to a common manifold terminating in a combustion chamber. Bleed lines shall not terminate in positive-pressure-type combustion chambers. [NFPA 54:9.1.18]

    903.0 Air-Conditioning Appliances.

    903.1 Electric Air Conditioners. Electric air conditioning systems designed for permanent installation shall comply with UL 1995 or UL 60335-2-40.

    903.2 Gas-Fired Air Conditioners and Heat Pumps. Gas-fired air conditioners shall comply with Section 903.2.1 through Section 903.2.7.

    903.2.1 Application. Gas-fired air conditioners and heat pumps shall be listed in accordance with ANSI Z21.40.1/CGA 2.91 or ANSI Z21.40.2/CGA 2.92.

    [NFPA 54:10.2.1]

    903.2.2 Independent Gas Piping. Gas piping serving heating appliances shall be permitted to also serve cooling appliances where heating and cooling appliances cannot be operated simultaneously. [NFPA 54:10.2.2]

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    INSTALLATION OF SPECIFIC APPLIANCES

    904.3.3 Listed and Unlisted Units. Central heating furnaces and low-pressure boilers shall be permitted to be installed with reduced clearances to combustible material, provided that the combustible material or appliance is protected as described in Table 303.10.1 and Figure 303.10.1(1) through Figure 303.10.1(3), and such reduction is allowed by the manufacturer’s installation instructions. [NFPA 54:10.3.3.3]

    904.3.4 Front Clearance. Front clearance shall be sufficient for servicing the burner and the furnace or boiler.

    [NFPA 54:10.3.3.4]

    904.3.5 Adjacent to Plaster or Noncombustible Materials. Where the furnace plenum is adjacent to plaster on metal lath or noncombustible material attached to combustible material, the clearance shall be measured to the surface of the plaster or other noncombustible finish where the clearance specified is 2 inches (51 mm) or less. [NFPA 54:10.3.3.5]

    904.3.6 Interference. The clearances to these appliances shall not interfere with combustion air, draft hood clearance and relief, and accessibility for servicing.

  • CMC § 10.11.4.1 High relevance — show source text

    [NFPA 54:10.11.4.1, 10.11.4.2] 917.5 Combustible Material Adjacent to Cooking Top. Food service ranges shall be installed to provide clearance to combustible material of not less than 18 inches (457 mm) horizontally for a distance up to 2 feet (610 mm) above the surface of the cooking top where the combustible material is not completely shielded by high shelving, a warming closet, or other system. Reduced combustible material clearances are

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    INSTALLATION OF SPECIFIC APPLIANCES

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    919.4 Floor-Mounted Units. Floor mounted units shall be

    installed in accordance with Section 919.4.1 and Section

    919.4.2.

    919.4.1 Clearances. Floor-mounted household cooking appliances, where installed on combustible floors, shall be set on their own bases or legs and shall not interfere with combustion air, accessibility for operation, and servicing. [NFPA 54:10.13.3]

    919.4.2 Vertical Clearance Above Cooking Top. Household cooking appliances shall have a vertical clearance above the cooking top of not less than 30 inches (762 mm) to combustible material or metal cabinets. A minimum clearance of 24 inches (610 mm) shall be permitted where one of the following is installed:

    (1) The underside of the combustible material or metal cabinet above the cooking top is protected with not less than [1] ⁄ 4 of an inch (6.4 mm) insulating millboard covered with sheet metal not less than 0.0122 of an inch (0.3099 mm) thick.

    (2) A metal ventilating hood of sheet metal not less than 0.0122 of an inch (0.3099 mm) thick is installed above the cooking top with a clearance of not less than [1] ⁄ 4 of an inch (6.4 mm) between the hood and the underside of the combustible material or metal

    cabinet, and the hood is not less than the width of the appliance and is centered over the appliance.

    (3) A listed cooking appliance or microwave oven installed over a listed cooking appliance shall be in accordance with the terms of the upper appliance’s listing and the manufacturer’s installation instructions. {NFPA 54:10.13.3.1} Microwave ovens shall comply with UL 923.

    919.5 Built-In Units. Built-in units shall be installed in accor dance with Section 919.5.1 and Section 919.5.2.

    919.5.1 Installation. Listed built-in household cooking appliances shall be installed in accordance with their listing and the manufacturer’s installation instructions. The installation shall not interfere with combustion air, accessibility for operation, and servicing. Unlisted builtin household cooking appliances shall not be installed in or adjacent to combustible material.

  • CMC § 307.4 High relevance — show source text

    (11)Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.

    An appliance shall be accompanied by clear and complete installation instructions, including required clearances from combustible other than mounting or adjacent surfaces, and temperature rating of field-installed wiring connections exceeding 140°F (60°C). 307.4 Absorption Units. Absorption units shall bear a permanent and legible factory-applied nameplate on which shall

    appear:

    (1) The name or trademark of the manufacturer.

    (2) The model number or equivalent.

    (3) The serial number.

    (4) The amount of refrigerant.

    (5) The refrigerant designation.

    (6) Hourly rating in Btu/h (kW).

    (7) The type of fuel approved for use with the unit.

    (8) Cooling capacity Btu/h (kW).

    (9) Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.

    (10)The symbol of an approved agency certifying compliance of the equipment with recognized standards.

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    GENERAL REGULATIONS

    308.0 Improper Location.

    308.1 General. Piping or equipment shall not be so located as to interfere with the normal use thereof or with the normal operation and use of windows, doors, or other required facilities.

    309.0 Workmanship.

    309.1 Engineering Practices. Design, construction, and workmanship shall comply with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this code.

    309.2 Concealing Imperfections. It shall be unlawful to conceal cracks, holes, or other imperfections in materials by welding, brazing, or soldering, by using therein or thereon paint, wax, tar, solvent cement, other leak-sealing or repair agent.

    309.3 Installation Practices. Mechanical systems shall be installed in a manner that is in accordance with this code, applicable standards, and the manufacturer’s installation instructions. All mechanical systems shall be in accordance with construction documents approved by the Authority Having Jurisdiction.

    310.0 Condensate Wastes and Control.

    310.1 Condensate Disposal. Condensate from air washers, air-cooling coils, condensing appliances, and the overflow from evaporative coolers and similar water-supplied equipment or similar air-conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area. Where discharged into the drainage system, equipment shall drain by means of an indirect waste pipe. The waste pipe shall have a slope of not less than [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size in

    accordance with Section 310.3 or Section 310.4 for air-cooling coils or condensing appliances, respectively. Condensate or wastewater shall not drain over a public way.

  • CMC § 916.4 High relevance — show source text

    vent instead of the rear wall of the unit heater. A unit

    heater listed for reduced clearances shall be installed in accordance with its listing and the manufacturer’s installation instructions.

    (2) Floor-mounted-type unit heaters installed on combustible floors shall be listed for such installation.

    (3) Combustible floors under unlisted floor-mounted unit heaters shall be protected in an approved man ner.

    (4) Clearances for servicing shall be in accordance with the manufacturer’s instructions.

    916.4 Combustion and Circulating Air. Combustion and circulating air shall be provided in accordance with Section 701.0. [NFPA 54:10.24.4]

    916.5 Ductwork. A unit heater shall not be attached to a warm air duct system unless listed and marked for such installation. [NFPA 54:10.24.5] 916.6 Installation in Commercial Garages and Air- craft Hangars. Unit heaters installed in garages for more than three motor vehicles or in aircraft hangars shall be installed in accordance with Section 303.11 and Section 303.12. [NFPA 54:10.24.6]

    916.7 Oil-Fired Unit Heaters. Oil-fired unit heaters shall comply with UL 731 and installed in accordance with the manufacturer’s installation instructions.

    917.0 Food Service Appliance, Floor-Mounted. 917.1 Application. Floor-mounted food service appliances shall be listed in accordance with ANSI Z83.11/CSA 1.8.

    [NFPA 54:10.11.1] 917.2 Clearance for Listed Appliances. Floor-mounted food service appliances, such as ranges for hotels and restaurants, deep fat fryers, unit broilers, kettles, steam cookers, steam generators, and baking and roasting ovens, shall be installed not less than 6 inches (152 mm) from combustible material except that at least a 2 inch (51 mm) clearance shall be maintained between a draft hood and combustible material. Floor-mounted food service appliances listed for installation at lesser clearances shall be installed in accordance with its listing and the manufacturer’s installation instructions. Appliances designed and marked, “For use only in noncombustible locations,” shall not be installed elsewhere. [NFPA 54:10.11.2] 917.3 Mounting on Combustible Floors. Floor-mounted food service appliances that are listed specifically for installation on floors constructed of combustible material shall be permitted to be installed on combustible floors in accordance with its listing and the manufacturer’s installation instructions. [NFPA 54:10.11.3.1]

    917.3.1 Not Listed for Mounting on Combustible Floors. Floor-mounted food service appliances that are not listed for installation on a combustible floor shall be

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    such as to interfere with combustion air and accessibility. Unlisted room heaters shall be installed with clearances from combustible material not less than the following:

    (1) Circulating type room heaters having an outer jacket surrounding the combustion chamber, arranged with openings at top and bottom so that air circulates between the inner and outer jacket, and without openings in the outer jacket to permit direct radiation, shall have clearance at sides and rear of not less than 12 inches (305 mm).

  • CMC § 920.3 High relevance — show source text

    920.3 Oil-Burning Ranges. Oil-burning ranges shall comply with UL 896 and installed in accordance with the manufacturer’s installation instructions.

    921.0 Open-Top Broiler Units.

    921.1 Application. Open-top broiler units shall be listed in accordance with ANSI Z83.11/CSA 1.8 or ANSI/CSA

    Z21.1/CSA 1.1 and installed in accordance with the manu facturer’s installation instructions. [NFPA 54:10.17.1]

    921.2 Protection Above Domestic Units. Domestic opentop broiler units shall be provided with a metal ventilating hood not less than 0.0122 of an inch (0.3099 mm) thick with a clearance of not less than [1] ⁄ 4 of an inch (6.4 mm) between the hood and the underside of combustible material or metal cabinets. A

    clearance of at least 24 inches (610 mm) shall be maintained between the cooking top and the combustible material or metal cabinet, and the hood shall be at least as wide as the open-top broiler unit and centered over the unit. Domestic open-top broiler units incorporating an integral exhaust system and listed for use without a ventilating hood shall not be required to be provided with a ventilating hood if installed in accordance with Section 919.4.2(1). [NFPA 54:10.17.2]

    921.3 Commercial Units. Commercial open-top broiler units shall be provided with ventilation in accordance with Chapter 5, Part II. {NFPA 54:10.17.3}

    922.0 Outdoor Cooking Appliances.

    922.1 Application. Outdoor cooking appliances shall be listed in accordance with ANSI Z83.11/CSA 1.8, ANSI Z21.58/CSA 1.6, or ANSI Z21.89/CSA 1.18, and installed in accordance with the manufacturer’s installation instructions.

    [NFPA 54:10.18]

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    923.0 Illuminating Appliances.

    923.1 Clearances for Listed Appliances. Listed illuminating appliances shall be installed in accordance with their listing and the manufacturer’s installation instructions. {NFPA 54:10.14.1}

    923.2 Clearances for Unlisted Appliances. Clearances for unlisted illuminating appliances shall comply with the following:

    (1) Unlisted enclosed illuminating appliances installed outdoors shall be installed with clearances in any direction from combustible material of not less than 12 inches (305 mm). [NFPA 54:10.14.2.1(1)]

    (2) Unlisted enclosed illuminating appliances installed indoors shall be installed with clearances in any direction from combustible material of not less than 18 inches

    (457 mm). [NFPA 54:10.14.2.1(2)]

    923.2.1 Open-Flame Type. Clearance shall comply with the following:

Frequently asked questions

Must I always follow the appliance nameplate over the Code?

Yes. For listed appliances, the Code requires installation in accordance with the listing and the manufacturer’s installation instructions; nameplate/listing clearances control when present (§303.1) .

Can I reduce clearance by adding a heat shield on the wall?

Possibly — the Code allows reduced clearances according to Table 303.10.1 or an appliance’s listing. You must follow the protective methods and the table or listing; do not invent a shield solution without Code or listing support (§303.10.1) .

What if my appliance is unlisted and the manufacturer gives no guidance?

If the appliance is unlisted, you need AHJ approval and must install with clearances acceptable to the Authority Having Jurisdiction or follow Table 303.10.1 if the manufacturer permits reduced clearances; otherwise use Code defaults in appliance chapters where provided (§303.3, §303.10.1) .

Are service/access clearances the same as clearance to combustibles?

No. Service/access clearances (for servicing, removal, cleaning) are separate — the Code generally requires 30 inches of working space unless otherwise specified (§304.1). Do both checks: service clearance and combustible clearance (§304.1, §303.10) .

Where is Table 303.10.1 — do I need it?

Table 303.10.1 is in the Code and governs allowed clearance reductions and protective methods; consult it whenever you plan to install at reduced clearances or to apply shielding/protection methods (§303.10.1) .

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