CMC · California Mechanical Code
How must gas vents be installed and where can they terminate?
In plain terms: install gas vents per the manufacturer and the California Mechanical Code. Small vents (≤12") that are at least 8 ft from a wall follow the roof‑slope table; larger vents or vents closer than 8 ft must stand at least 2 ft above the roof penetration and nearby building parts. Apply extra clearances for Type B/L (5 ft), wall furnaces (12 ft), and forced‑air inlets (3 ft). Use listed caps, don’t pierce double‑wall vent interiors, and use the metal shield where a vent passes through insulation (see § 802.6 and § 802.6.1) .
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Gas vents must be installed per the appliance and vent manufacturer’s instructions and must meet the termination and clearance rules in § 802.6 and § 802.6.1 of the California Mechanical Code (CMC) . Small vents (12 inches / 300 mm or less) that are at least 8 feet from a vertical wall terminate according to the sizing/roof‑slope table and figure; larger vents or those closer than 8 feet to walls must meet fixed vertical clearances (for example, 2 feet above the highest roof penetration and portions of the building within 10 feet) . Additional specific clearances apply for Type B/L, Type B‑W (wall furnaces), forced‑air inlets, and other special systems — see § 802.6.1 for each required dimension .
The single most important rule: terminate gas vents so the termination meets the roof‑height/clearance table and the specific vertical separations in § 802.6.1 — and always follow the vent manufacturer's instructions. § 802.6.1 .
Requirements in detail
Installation basics (what the code explicitly requires)
- Install all gas vents in accordance with the manufacturer’s instructions — this is the baseline requirement in § 802.6 (1).
- A Type B‑W vent must have a listed capacity not less than the vented wall furnace it serves ( § 802.6 (2) ).
- Gas vents installed inside masonry chimneys must follow the manufacturer’s instructions and be labeled at the point they enter the chimney (label wording is specified) ( § 802.6 (3) ).
- Do not penetrate the inner wall of double‑wall gas vents with screws, rivets or similar fasteners except at the permitted transition locations ( § 802.6 (4) ).
Termination locations — how to decide where a vent may end
The code divides terminations by vent size and proximity to vertical obstructions, then adds appliance‑type and accessory clearances:
- If the vent is 12 inches (300 mm) or less and is located not less than 8 feet (2438 mm) from a vertical wall or similar obstruction, terminate above the roof following Figure 802.6.1 and Table 802.6.1 (roof‑slope height values) ( § 802.6.1 (1)(a) ).
- If the vent is over 12 inches (300 mm) or is located less than 8 feet (2438 mm) from a vertical wall, the vent shall terminate not less than 2 feet (610 mm) above (a) the highest point where it passes through the roof and (b) any portion of a building within 10 feet (3048 mm) horizontally ( § 802.6.1 (1)(b) ).
- Termination exceptions/special systems: industrial appliances, direct‑vent systems, appliances with integral vents, mechanical draft systems and ventilating hoods are handled by their specific sections ( § 802.6.1 (1)(c)–(g) ).
Specific additional vertical clearances:
- Type B or Type L gas vents: terminate at least 5 feet (1524 mm) vertically above the highest connected appliance draft hood or flue collar ( § 802.6.1 (2) ).
- Type B‑W (wall furnace) vents: terminate at least 12 feet (3658 mm) vertically above the bottom of the wall furnace ( § 802.6.1 (3) ).
- Vents that pass through roof flashing must extend through the flashing/thimble and terminate with a listed cap or listed roof assembly ( § 802.6.1 (6) ).
- A gas vent must terminate at least 3 feet (914 mm) above a forced‑air inlet located within 10 feet (3048 mm) ( § 802.6.1 (7) ).
Insulation protection and shields
- Where a vent passes through an insulated assembly, install an approved metal shield of at least 26‑gauge (0.0179 in / 0.45 mm) steel that extends not less than 2 inches (51 mm) above the insulation and is secured per the manufacturer’s instructions ( § 802.6.1.1 ).
Table — decision‑relevant dimensions and where to find them in the code
| Decision / condition | Required minimum / action | Code Reference |
|---|---|---|
| Vent size ≤ 12 in and ≥ 8 ft from vertical wall | Terminate above roof per Figure 802.6.1; use Table 802.6.1 for minimum H (roof‑slope) | § 802.6.1 (1)(a) |
| Vent size > 12 in or < 8 ft from vertical wall | Terminate ≥ 2 ft (610 mm) above highest roof penetration and ≥ 2 ft above any building portion within 10 ft horizontally | § 802.6.1 (1)(b) |
| Type B or L vent | Terminate ≥ 5 ft (1524 mm) above highest connected draft hood/flue collar | § 802.6.1 (2) |
| Type B‑W (wall furnace) | Terminate ≥ 12 ft (3658 mm) above bottom of wall furnace | § 802.6.1 (3) |
| Forced‑air inlet within 10 ft | Vent must be ≥ 3 ft (914 mm) above that inlet | § 802.6.1 (7) |
| Insulated assembly penetration | Install 26‑gauge steel shield, extend ≥ 2 in (51 mm) above insulation | § 802.6.1.1 |
| Double‑wall vent fasteners | Do not penetrate inner wall with screws/rivets except at allowed transitions | § 802.6 (4) |
| Roof termination assembly | Vent must extend through flashing/thimble and end with a listed cap/roof assembly | § 802.6.1 (6) |
Where roof slope H values come from
- The Table 802.6.1 (roof slopes → minimum H) provides the minimum height H for caps on small vents (≤12 in) when the vent is ≥8 ft from vertical walls. See Table 802.6.1 and Figure 802.6.1 (CMC) for the slope lookup (examples: flat to 6/12 → H = 1.0 ft; over 11/12 to 12/12 → H = 4.0 ft, etc.) ( § 802.6.1 and Table 802.6.1 ).
Exceptions & special cases
- The termination rules in § 802.6.1 (1)(c)-(g) defer to the special rules for: industrial appliances (§ 802.2.5), direct‑vent systems (§ 802.2.6), appliances with integral vents (§ 802.2.7), mechanical draft systems (§ 802.3.3–3.3.4), and ventilating hoods/exhaust systems (§ 802.3.4) — follow those sections where applicable rather than the general rules in § 802.6.1 .
- Decorative shrouds are prohibited at vent terminations unless the shroud is listed for use with that venting system and installed per the manufacturer’s instructions ( § 802.6.1 (5) ) .
- A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves/parapets except where the referenced special sections allow otherwise ( § 802.6.1 (4) ) .
If a portion of a required provision above is missing from the retrieval, the text is explicitly noted in the code file excerpts; do not assume alternate dimensions beyond what the code text specifies here.
Common mistakes
- Misreading the two‑part rule for small vents: size (≤ 12 in) and distance (≥ 8 ft) must both be satisfied to use the Figure/Table method — otherwise the 2‑ft rule applies ( § 802.6.1 (1)(a), (b) ) .
- Forgetting the appliance‑specific vertical clearances (e.g., Type B/L = 5 ft, Type B‑W = 12 ft) and simply using the 2‑ft roof clearance — always apply the largest applicable clearance ( § 802.6.1 (2)–(3) ) .
- Installing decorative shrouds or caps that are not listed for the specific vent system ( § 802.6.1 (5) ) .
- Penetrating the inner wall of a double‑wall gas vent with screws/rivets (prohibited except at allowed transitions) ( § 802.6 (4) ) .
- Terminating too close to a forced‑air inlet (must be ≥ 3 ft above any inlet within 10 ft) ( § 802.6.1 (7) ) .
- Failing to use a listed cap or roof assembly or to extend the vent through proper flashing/thimble ( § 802.6.1 (6) ) .
Worked example — concrete scenario
Scenario: You have a Type B gas‑fired appliance with a vent connector that is 8 in diameter (≤12 in). The vent outlet through the roof is located 6 ft horizontally from a vertical building wall (so it is less than the 8‑ft threshold). The highest connected draft hood is located in the appliance room and its outlet is 1 ft below the roof penetration plane.
Step 1 — apply the size/proximity test:
- Vent is ≤ 12 in but is less than 8 ft from the vertical wall → the Figure/Table method (for vents ≥8 ft from wall) does NOT apply. Instead use the rule in § 802.6.1 (1)(b): termination must be not less than 2 ft (610 mm) above the highest point where it passes through the roof and not less than 2 ft above any building portion within 10 ft horizontally.
Step 2 — apply the Type B appliance rule:
- Type B vent must also terminate at least 5 ft (1524 mm) above the highest connected appliance draft hood or flue collar ( § 802.6.1 (2) ).
Step 3 — compute required termination elevation (take the largest required clearance):
- 2 ft above roof penetration (per 1(b)) → 2.0 ft above roof.
- 5 ft above draft hood: draft hood is 1 ft below roof, so 5 ft above draft hood = 4 ft above roof.
- The controlling requirement is the larger: 4 ft above roof. Install termination at or above this elevation and cap with a listed cap per § 802.6.1 (6).
Brief summary of calculation: compute each applicable clearance requirement independently and provide the termination that satisfies the largest of them.
Related provisions
- § 802.6 — Gas vents (installation basics, fasteners, labeling)
- § 802.6.1 — Gas vent termination rules (size/proximity, Type B/L, Type B‑W, caps, forced‑air inlet)
- § 802.6.1.1 — Insulation protection shield requirements where vents pass through insulated assemblies
- § 802.6.5 — Marking (labeling) of gas vents in areas with solid/liquid fuel use (see § 802.6.5 in the CMC excerpts)
- § 802.7 / § 802.7.2 — Single‑wall metal pipe termination rules (separate termination heights)
- Special‑system sections referenced by § 802.6.1 (see § 802.2.5, § 802.2.6, § 802.2.7 and § 802.3.3–3.3.4 for industrial, direct‑vent, integral vent and mechanical draft systems)
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 12.6.8.2 High relevance — show source text
Exception: Direct vent appliances designed for installation in a solid-fuel-burning fireplace where installed in accordance with the manufacturer’s installation instructions. [NFPA 54:12.6.8.2] 802.6 Gas Vents. The installation of gas vents shall meet the following requirements:
(1) Gas vents shall be installed in accordance with the manufacturer’s installation instructions.
(2) A Type B-W gas vent shall have a listed capacity not less than that of the listed vented wall furnace to which it is
connected.
(3) Gas vents installed within masonry chimneys shall be installed in accordance with the manufacturer’s installation instructions. Gas vents installed within masonry chimneys shall be identified with a permanent label installed at the point where the vent enters the chimney. The label shall contain the following language: “This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel–burning appliances or incinerators.”
(4) Screws, rivets, and other fasteners shall not penetrate the inner wall of double-wall gas vents, except at the transition from the appliance draft hood outlet, flue collar, or single-wall metal connector to a double-wall vent.
[NFPA 54:12.7.2] 802.6.1 Gas Vent Termination. The termination of gas vents shall comply with the following requirements:
(1) A gas vent shall terminate in accordance with one of the following:
(a) Gas vents that are 12 inches (300 mm) or less in size and located not less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall
terminate above the roof in accordance with Figure 802.6.1 and Table 802.6.1.
(b) Gas vents that are over 12 inches (300 mm) in size or are located less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall
terminate not less than 2 feet (610 mm) above the highest point where they pass through the roof and not less than 2 feet (610 mm) above a portion of a building within 10 feet (3048 mm) horizontally.
(c) Industrial appliances as provided in Section 802.2.5.
(d) Direct vent systems as provided in Section 802.2.6.
(e) Appliances with integral vents as provided in Section 802.2.7.
(f) Mechanical draft systems as provided in Section 802.3.3 through Section 802.3.3.4.
(g) Ventilating hoods and exhaust systems as provided in Section 802.3.4.
(2) A Type B or a Type L gas vent shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar.
(3) A Type B-W gas vent shall terminate at least 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.
(4) A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Section 802.2.6 and Section 802.3.3 through Section 802.3.3.4.
(5) Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with the manufac turer’s installation instructions.
CMC § 12.7.2 High relevance — show source text
(4) Screws, rivets, and other fasteners shall not penetrate the inner wall of double-wall gas vents, except at the transition from the appliance draft hood outlet, flue collar, or single-wall metal connector to a double-wall vent.
[NFPA 54:12.7.2]
509.6.1 Gas Vent Termination. The termination of gas vents shall comply with the following requirements:
(1) A gas vent shall terminate in accordance with one of the following:
(a) Gas vents that are 12 inches (300 mm) or less in size and located not less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall
terminate above the roof in accordance with Figure 509.6.1 and Table 509.6.1.
(b) Gas vents that are over 12 inches (300 mm) in size or are located less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall terminate not less than 2 feet (610 mm) above the highest point where they pass through the roof and not less than 2 feet (610 mm) above any portion of a building within 10 feet (3048 mm) horizontally.
(c) Industrial appliances as provided in Section 509.2.5.
(d) Direct-vent systems as provided in Section 509.2.6.
(e) Appliances with integral vents as provided in Section 509.2.7.
(f) Mechanical draft systems as provided in Section 509.3.3 through Section 509.3.3.4.
(g) Ventilating hoods and exhaust systems as provided in Section 509.3.4.
(2) A Type B or a Type L gas vent shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar.
(3) A Type B-W gas vent shall terminate at least 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.
(4) A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Section 509.2.6 and Section 509.3.3 through Section 509.3.3.4.
(5) Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with the manufac turer’s installation instructions.
(6) All gas vents shall extend through the roof flashing, roof jack, or roof thimble and terminate with a listed cap or listed roof assembly.
(7) A gas vent shall terminate at least 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm). [NFPA 54:12.7.3]
FIGURE 509.6.1
TERMINATION LOCATIONS FOR GAS
VENTS WITH LISTED CAPS 12 INCHES OR LESS IN SIZE
AT LEAST 8 FEET FROM A VERTICAL WALL
[NFPA 54: FIGURE 12.7.3]
TABLE 509.6.1
ROOF SLOPE HEIGHTS
[NFPA 54: TABLE 12.7.3]
CMC § 802.2.6 High relevance — show source text
(3) A Type B-W gas vent shall terminate at least 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.
(4) A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Section 802.2.6 and Section 802.3.3 through Section 802.3.3.4.
(5) Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with the manufac turer’s installation instructions.
(6) All gas vents shall extend through the roof flashing, roof jack, or roof thimble and terminate with a listed cap or listed roof assembly.
(7) A gas vent shall terminate at least 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm). [NFPA 54:12.7.3]
FIGURE 802.6.1
TERMINATION LOCATIONS FOR
GAS VENTS WITH LISTED CAPS 12 INCHES OR LESS IN
SIZE NOT LESS THAN 8 FEET FROM A VERTICAL WALL
[NFPA 54: FIGURE 12.7.3]
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CHIMNEYS AND VENTS
TABLE 802.6.1
ROOF SLOPE HEIGHTS
[NFPA 54: TABLE 12.7.3]
ROOF SLOPE H (minimum) (feet)
Flat to6⁄121.0
Over6⁄12 to7⁄121.25
Over7⁄12 to8⁄121.5
Over8⁄12 to9⁄122.0
Over9⁄12 to10⁄122.5
Over10⁄12 to11⁄123.25 Over11⁄12 to12⁄12 4.0
Over12⁄12 to14⁄125.0
Over14⁄12 to16⁄126.0
Over16⁄12 to18⁄127.0
Over18⁄12 to20⁄127.5
Over20⁄12 to21⁄128.0 For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm
802.6.1.1 Insulation Protection Shield. Where a vent passes through an insulated assembly, an approved metal shield constructed of steel having a thickness of not less than 0.0179 inch (0.45 mm) (26 gauge) shall be installed between the vent and insulation. The shield shall extend not less than 2 inches (51 mm) above the insulation and be secured to the structure in accordance with the manufacturer’s
installation instructions.
**802.6.2 Size of Gas Vents.
CMC § 12.6.7 High relevance — show source text
[NFPA 54:12.6.7] 509.5.10 Space Surrounding Lining or Vent. The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry chimney shall not be used to vent another appli ance.
Exception: The insertion of another liner or vent within the chimney as provided in this code and the liner or vent manufacturer’s instructions. [NFPA 54:12.6.8.1] 509.5.10.1 Combustion Air. The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry, metal, or factory-built chimney flue shall not be used to supply combustion air.
Exception: Direct-vent appliances designed for installation in a solid fuel-burning fireplace where installed in accordance with the manufacturer’s installation instructions. [NFPA 54:12.6.8.2] 509.6 Gas Vents. The installation of gas vents shall meet the following requirements:
(1) Gas vents shall be installed in accordance with the manufacturer’s installation instructions.
(2) A Type B-W gas vent shall have a listed capacity not less than that of the listed vented wall furnace to which it is
connected.
(3) Gas vents installed within masonry chimneys shall be installed in accordance with the manufacturer’s installation instructions. Gas vents installed within masonry
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WATER HEATERS
chimneys shall be identified with a permanent label installed at the point where the vent enters the chimney. The label shall contain the following language: “This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel–burning appliances or incinerators.”
(4) Screws, rivets, and other fasteners shall not penetrate the inner wall of double-wall gas vents, except at the transition from the appliance draft hood outlet, flue collar, or single-wall metal connector to a double-wall vent.
[NFPA 54:12.7.2]
509.6.1 Gas Vent Termination. The termination of gas vents shall comply with the following requirements:
(1) A gas vent shall terminate in accordance with one of the following:
(a) Gas vents that are 12 inches (300 mm) or less in size and located not less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall
terminate above the roof in accordance with Figure 509.6.1 and Table 509.6.1.
(b) Gas vents that are over 12 inches (300 mm) in size or are located less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall terminate not less than 2 feet (610 mm) above the highest point where they pass through the roof and not less than 2 feet (610 mm) above any portion of a building within 10 feet (3048 mm) horizontally.
(c) Industrial appliances as provided in Section 509.2.5.
(d) Direct-vent systems as provided in Section 509.2.6.
(e) Appliances with integral vents as provided in Section 509.2.7.
(f) Mechanical draft systems as provided in Section 509.3.3 through Section 509.3.3.4.
CMC § 802.2.5. High relevance — show source text
(b) Gas vents that are over 12 inches (300 mm) in size or are located less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall
terminate not less than 2 feet (610 mm) above the highest point where they pass through the roof and not less than 2 feet (610 mm) above a portion of a building within 10 feet (3048 mm) horizontally.
(c) Industrial appliances as provided in Section 802.2.5.
(d) Direct vent systems as provided in Section 802.2.6.
(e) Appliances with integral vents as provided in Section 802.2.7.
(f) Mechanical draft systems as provided in Section 802.3.3 through Section 802.3.3.4.
(g) Ventilating hoods and exhaust systems as provided in Section 802.3.4.
(2) A Type B or a Type L gas vent shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar.
(3) A Type B-W gas vent shall terminate at least 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.
(4) A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Section 802.2.6 and Section 802.3.3 through Section 802.3.3.4.
(5) Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with the manufac turer’s installation instructions.
(6) All gas vents shall extend through the roof flashing, roof jack, or roof thimble and terminate with a listed cap or listed roof assembly.
(7) A gas vent shall terminate at least 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm). [NFPA 54:12.7.3]
FIGURE 802.6.1
TERMINATION LOCATIONS FOR
GAS VENTS WITH LISTED CAPS 12 INCHES OR LESS IN
SIZE NOT LESS THAN 8 FEET FROM A VERTICAL WALL
[NFPA 54: FIGURE 12.7.3]
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CHIMNEYS AND VENTS
TABLE 802.6.1
ROOF SLOPE HEIGHTS
[NFPA 54: TABLE 12.7.3]
CMC § 509.2.6 High relevance — show source text
(2) A Type B or a Type L gas vent shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar.
(3) A Type B-W gas vent shall terminate at least 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.
(4) A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Section 509.2.6 and Section 509.3.3 through Section 509.3.3.4.
(5) Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with the manufac turer’s installation instructions.
(6) All gas vents shall extend through the roof flashing, roof jack, or roof thimble and terminate with a listed cap or listed roof assembly.
(7) A gas vent shall terminate at least 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm). [NFPA 54:12.7.3]
FIGURE 509.6.1
TERMINATION LOCATIONS FOR GAS
VENTS WITH LISTED CAPS 12 INCHES OR LESS IN SIZE
AT LEAST 8 FEET FROM A VERTICAL WALL
[NFPA 54: FIGURE 12.7.3]
TABLE 509.6.1
ROOF SLOPE HEIGHTS
[NFPA 54: TABLE 12.7.3]
ROOF SLOPE H (minimum) (feet)
Flat to6⁄121.0
Over6⁄12 to7⁄121.25
Over7⁄12 to8⁄121.5
Over8⁄12 to9⁄122.0
Over9⁄12 to10⁄122.5
Over10⁄12 to11⁄123.25
Over11⁄12 to12⁄124.0
Over12⁄12 to14⁄125.0
Over14⁄12 to16⁄126.0
Over16⁄12 to18⁄127.0
Over18⁄12 to20⁄127.5
Over20⁄12 to21⁄128.0 For SI Units: 1 inch = 25.4 mm, 1 foot = 304.8 mm
509.6.1.1 Insulation Protection Shield. Where a vent passes through an insulated assembly, an approved metal shield constructed of steel having a thickness of not less than 26 gauge (0.0179 inch) (0.45 mm) (No. 26 gauge) shall be installed between the vent and insulation. The shield shall extend not less than 2 inches (51 mm) above the insulation and be secured to the structure in accordance with the
manufacturer’s installation instructions.
509.6.2 Size of Gas Vents. Venting systems shall be sized and constructed in accordance with Section
CMC § 5.9.2 High relevance — show source text
(1) Check valves.
(2) Three-way valves (of the type that completely closes one side before starting to open the other side).
(3) Reverse flow indicators controlling positive shutoff valves.
(4) Normally closed air-actuated positive shutoff pressure regulators. [NFPA 54:5.9.2] 1308.11 Low-Pressure Protection. A protective device shall be installed between the meter and the appliance or equipment if the operation of the appliance or equipment is such that it could produce a vacuum or a dangerous reduction in gas pressure at the meter. Such protective devices include, but are not limited to, mechanical, diaphragm-operated, or electrically operated low-pressure shutoff valves. [NFPA 54:5.10]
1308.12 Shutoff Valves. Shutoff valves shall be selected in
accordance with Table 1308.12. Shutoff valves of size 1 inch
(25 mm) National Pipe Thread and smaller shall be listed and labeled. Where used outdoors, such use shall be in accordance with the manufacturer’s recommendation. [NFPA 54:5.11]
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FUEL GAS PIPING
Exceptions: (1) A regulator and vent limiting means combination listed as complying with CSA/ANSI Z21.80/CSA 6.22, shall not be required to be vented to the outdoors.
(2) A listed gas appliance regulator factory equipped with a vent limiting device is not required to be vented to the outdoors.
(2) Materials for vent piping shall be in accordance with Section 1308.4 through Section 1308.4.10.5. (3) The vent terminus shall be designed to prevent the entry of water, insects, and other foreign matter that could cause blockage. (4) Vent piping shall be installed to minimize static loads and bending moments placed on the regulators and gas pressure control devices.
(5) Vents shall terminate not less than 3 feet (914 mm) from a possible source of ignition. (6) At locations where a vent termination could be submerged during floods or snow accumulations, an antiflood-type breather vent fitting shall be installed, or the vent terminal shall be located above the height of the expected floodwaters or snow.
(7) Vent piping from pressure regulators and gas pressure controls shall not be connected to a common manifold that serves a bleed line from a diaphragm-type gas valve.
[NFPA 54:5.14]
1309.0 Excess Flow Valve.
1309.1 General. Where automatic excess flow valves are installed, they shall be listed in accordance with ANSI Z21.93/CSA 6.30 and shall be sized and installed in accordance with the manufacturers’ instructions. [NFPA 54:5.12]
1310.0 Gas Piping Installation. 1310.1 Piping Underground. Underground gas piping shall be installed with sufficient clearance from any other underground structure to avoid contact therewith, to allow maintenance, and to protect against damage from proximity to other structures. Underground plastic piping shall be installed with sufficient clearance or shall be insulated from any source of heat so as to prevent the heat from impairing the serviceability of the pipe.
CMC § 1208.5 High relevance — show source text
FUEL GAS PIPING
(2) A listed gas appliance regulator factory equipped with a vent limiting device is not required to be vented to the outdoors.
(2) Materials for vent piping shall be in accordance with Section 1208.5 through Section 1208.5.12.5.
(3) The vent terminus shall be designed to prevent the entry of water, insects, and other foreign matter that could cause blockage.
(4) Vent piping shall be installed to minimize static loads and bending moments placed on the regulators and gas pressure control devices.
(5) Vents shall terminate not less than 3 feet (914 mm) from a possible source of ignition.
(6) At locations where a vent termination could be submerged during floods or snow accumulations, an antiflood-type breather vent fitting shall be installed, or the vent terminal shall be located above the height of the expected flood waters or snow.
(7) Vent piping from pressure regulators and gas pressure controls shall not be connected to a common manifold
that serves a bleed line from a diaphragm-type gas valve.
[NFPA 54:5.14]
TABLE 1208.13
MANUAL GAS VALVE STANDARDS
[NFPA 54: TABLE 5.11]
1209.0 Excess Flow Valve.
1209.1 General. Where automatic excess flow valves are installed, they shall be listed in accordance with ANSI Z21.93/CSA 6.30 and shall be sized and installed in accor dance with the manufacturers’ instructions. [NFPA 54:5.12]
1210.0 Gas Piping Installation.
1210.1 Piping Underground. Underground gas piping shall be installed with sufficient clearance from any other underground structure to avoid contact therewith, to allow maintenance, and to protect against damage from proximity to other structures. Underground plastic piping shall be installed with sufficient clearance or shall be insulated from any source of heat so as to prevent the heat from impairing the serviceability of the pipe. [NFPA 54:7.1.1.1 – 7.1.1.2]
1210.1.1 Cover Requirements. Underground piping systems shall be installed with a minimum of 12 inches (305 mm) of cover. The minimum cover shall be increased to 18 inches (457 mm) if external damage to the pipe or tubing from external forces is likely to result. Where a minimum of 12 inches (305 mm) of cover cannot be provided, the piping shall be installed in conduit.
[NFPA 54:7.1.2.1 – 7.1.2.1(B)]
1210.1.2 Trenches. The trench shall be graded so that the pipe has a firm, substantially continuous bearing on the bottom of the trench. [NFPA 54:7.1.2.2]
1210.1.2.1 Backfilling. Where flooding of the trench is done to consolidate the backfill, care shall be exercised to see that the pipe is not floated from its firm bearing on the trench bottom. [NFPA 54:7.1.2.3]
1210.1.3 Protection Against Corrosion. Steel pipe and steel tubing installed underground shall be installed in accordance with Section 1210.1.3.1 through Section 1210.1.3.9. [NFPA 54:7.1.3]
CMC § 10-09 High relevance — show source text
B. PG&E will position gas regulators to minimize the length of the regulator vent lines and to ensure adequate venting capacity.
- “ −C. PG&E will specify regulator vent lines, in accordance with Gas Design Standard H 93, Regulator Vent Lines
- Regulator Vent Locations
A. Service regulator vents must terminate in a safe outside location that complies with the following criteria:
(1) The regulator vent must not terminate near any sources of ignition or openings into the building. The regulator vent must be 36 inches horizontally from sources of ignition and openings into the building, and this clearance area will extend 10 feet above and 36 inches below the regulator vent termination.
(2) A minimum lateral distance of 8 feet from a forced air intake. This includes the intake vents for the gas meter room.
(3) Within any location that is under display platforms or show windows in commercial buildings, including any permanent, elevated, display floors or platforms associated with the window.
(4) Within any location that is under building overhangs, where the overhang is likely to direct venting gas into a building opening.
B. Vents for all natural gas regulator and gas monitor diaphragm equipment must terminate above a reasonable flood level. Regulator vent extensions must be separate lines, terminated so they are protected from the rain and provided with screened fittings to prevent insects and other debris from entering the vent.
C. Vent locations must have final approval by PG&E.
Page 6 of 11 PG&E Internal Information, SL2 © 2013 Pacific Gas & Electric Company. All Rights Reserved. Prepared by: AAJ7
Gas Meter Room J-16
Rev. #03a 10-09-13
Requirements for PG&E-Owned Equipment
- Natural Gas Metering
Electrical grounding or bonding to PG&E’s metering facility piping or equipment or to customer-owned house lines inside of the meter room is not permitted.
- Land-Line Cable and Conduit
Customers with an estimated average use of 10,000 therms per month or more are required to install, own, and maintain a nominal 1” diameter conduit and a telephone cable. PG&E’s requirements for the conduit are described below.
A. Applicant/customer must extend the conduit and telephone cable from the closest telephone service location (i.e., outdoor “general purpose” area) to a location specified by PG&E that will be at or near the gas metering facilities. The maximum allowable distance from the telephone service location to PG&E’s gas meter is 50 feet.
B. Conduit must terminate within 3 feet of the gas meter location.
C. Applicant must install a conduit seal, inside the gas meter room, within 18 inches of the boundary where the conduit enters the gas meter room. There must be no conduit fitting between the boundary and the seal. PG&E will pour the conduit seal.
D. Applicant/customer is responsible for all charges and costs associated with installing the telephone facilities necessary to provide telephone service for PG&E’s gas metering facilities which are to be used for PG&E’s purposes.
E. PG&E is responsible for establishing telephone service and for the ongoing telephone service charges for gas metering purposes.
- Additional Equipment Needed to Support Gas Meters
Consideration must be given to the design requirements for:
A. Volume pulse output connections.
B. Electronic correctors.
CMC § 803.2 High relevance — show source text
** The size of the connectors and common segments of multistory venting systems for appliances listed for use with a Type B double-wall gas vent shall be in accordance with Table 803.2(1), provided all of the following apply: (1) The available total height ( H ) for each segment of a multistory venting system is the vertical distance between the level of the highest draft hood outlet or flue collar on that floor and the centerline of the next highest interconnection tee. (2) The size of the connector for a segment is determined from the appliance’s gas input rate and available connector rise and shall not be smaller
than the draft hood outlet or flue collar size.
(3) The size of the common vertical vent segment, and of the interconnection tee at the base of that segment, is based on the total appliance’s gas input rate entering that segment and its available total height. [NFPA 54:12.7.5.3]
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CHIMNEYS AND VENTS
FIGURE 802.6.3.1
PLAN VIEW OF PRACTICAL SEPARATION METHOD
FOR MULTISTORY GAS VENTING
[NFPA 54: FIGURE A.12.7.5.2]
802.6.4 Support of Gas Vents. Gas vents shall be supported and spaced in accordance with the manufacturer’s installation instructions. [NFPA 54:12.7.6]
802.6.5 Marking. In those localities where solid and liquid fuels are used extensively, gas vents shall be permanently identified by a label attached to the wall or ceiling at a point where the vent connector enters the gas vent. The label shall read: “This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel-burning appliances or incinerators.” The Authority Having Jurisdiction shall determine whether its area constitutes such a locality. [NFPA 54:12.7.7] 802.7 Single-Wall Metal Pipe. Single-wall metal pipe shall be constructed of galvanized sheet steel not less than 0.0304 of an inch (0.7722 mm) thick or of other approved, noncombustible, corrosion-resistant material. [NFPA 54:12.8.1]
802.7.1 Cold Climate. Uninsulated single-wall metal pipe shall not be used outdoors for venting appliances in regions where the 99 percent winter design temperature is below 32°F (0°C). [NFPA 54:12.8.2]
802.7.2 Termination. The termination of single-wall metal pipe shall meet the following requirements:
(1) Single-wall metal pipe shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood outlet or flue collar.
(2) Single-wall metal pipe shall extend at least 2 feet (610 mm) above the highest point where it passes through a roof of a building and at least 2 feet (610 mm) higher than any portion of a building within a horizontal distance of 10 feet (3048 mm).
(3) An approved cap or roof assembly shall be attached to the terminus of a single-wall metal pipe. [NFPA 54:12.8.3]
CMC § 1208.14.1 High relevance — show source text
1208.14.1 Special Local Conditions. Where local conditions include earthquake, tornado, unstable ground, or flood hazards, special consideration shall be given to increased strength and flexibility of piping supports and connections. [NFPA 54:5.13.2]
1208.15 Pressure Regulator and Pressure Control Venting. The venting of the atmospheric side of diaphragms in line pressure regulators, gas appliance regulators, and gas pressure limit controls shall be in accordance with all of the following:
(1) An independent vent pipe to the outdoors, sized in accordance with the device manufacturer’s instructions, shall be provided where the location of a device is such that a discharge of fuel gas will cause a hazard. For devices other than appliance regulators, vents are not required to be independent where the vents are connected to a common manifold designed in accordance with engineering methods to minimize backpressure in the event of diaphragm failure and such design is approved.
Exceptions:
(1) A regulator and vent limiting means combination listed as complying with CSA/ANSI Z21.80/CSA 6.22, shall not be required to be vented to the outdoors.
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FUEL GAS PIPING
(2) A listed gas appliance regulator factory equipped with a vent limiting device is not required to be vented to the outdoors.
(2) Materials for vent piping shall be in accordance with Section 1208.5 through Section 1208.5.12.5.
(3) The vent terminus shall be designed to prevent the entry of water, insects, and other foreign matter that could cause blockage.
(4) Vent piping shall be installed to minimize static loads and bending moments placed on the regulators and gas pressure control devices.
(5) Vents shall terminate not less than 3 feet (914 mm) from a possible source of ignition.
(6) At locations where a vent termination could be submerged during floods or snow accumulations, an antiflood-type breather vent fitting shall be installed, or the vent terminal shall be located above the height of the expected flood waters or snow.
(7) Vent piping from pressure regulators and gas pressure controls shall not be connected to a common manifold
that serves a bleed line from a diaphragm-type gas valve.
[NFPA 54:5.14]
TABLE 1208.13
MANUAL GAS VALVE STANDARDS
[NFPA 54: TABLE 5.11]
1209.0 Excess Flow Valve.
1209.1 General. Where automatic excess flow valves are installed, they shall be listed in accordance with ANSI Z21.93/CSA 6.30 and shall be sized and installed in accor dance with the manufacturers’ instructions. [NFPA 54:5.12]
1210.0 Gas Piping Installation.
CMC § 12.6.5.3 High relevance — show source text
The chimney flue shall be sized to properly vent the appliance.
[NFPA 54:12.6.5.3] 802.5.8.3 Combination Gas- and Oil-Burning Appliances. A single chimney flue serving a listed combination gas- and oil-burning appliance shall be sized in accordance with the appliance manufacturer’s instructions. [NFPA 54:12.6.5.4]
802.5.9 Support of Chimneys. All portions of chimneys shall be supported for the design and weight of the materials employed. Listed factory-built chimneys shall be supported and spaced in accordance with the manufacturer’s installation instructions. [NFPA 54:12.6.6]
156 2025 CALIFORNIA MECHANICAL CODE
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CHIMNEYS AND VENTS
802.5.10 Cleanouts. Where a chimney that formerly carried flue products from liquid or solid fuel-burning appliances is used with an appliance using fuel gas, an accessible cleanout shall be provided. The cleanout shall have a tight-fitting cover and be installed so its upper edge is at least 6 inches (152 mm) below the lower edge of the lowest chimney inlet opening. [NFPA 54:12.6.7] 802.5.11 Space Surrounding Lining or Vent. The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry chimney shall not be used to vent another appli ance.
Exception: The insertion of another liner or vent within the chimney as provided in this code and the liner or vent manufacturer’s instructions. [NFPA 54:12.6.8.1] 802.5.11.1 Combustion Air. The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry, metal or factory-built chimney flue shall not be used to supply combustion air.
Exception: Direct vent appliances designed for installation in a solid-fuel-burning fireplace where installed in accordance with the manufacturer’s installation instructions. [NFPA 54:12.6.8.2] 802.6 Gas Vents. The installation of gas vents shall meet the following requirements:
(1) Gas vents shall be installed in accordance with the manufacturer’s installation instructions.
(2) A Type B-W gas vent shall have a listed capacity not less than that of the listed vented wall furnace to which it is
connected.
(3) Gas vents installed within masonry chimneys shall be installed in accordance with the manufacturer’s installation instructions. Gas vents installed within masonry chimneys shall be identified with a permanent label installed at the point where the vent enters the chimney. The label shall contain the following language: “This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel–burning appliances or incinerators.”
(4) Screws, rivets, and other fasteners shall not penetrate the inner wall of double-wall gas vents, except at the transition from the appliance draft hood outlet, flue collar, or single-wall metal connector to a double-wall vent.
[NFPA 54:12.7.2] 802.6.1 Gas Vent Termination. The termination of gas vents shall comply with the following requirements:
(1) A gas vent shall terminate in accordance with one of the following:
Frequently asked questions
Can I cap a gas vent with any decorative shroud?
No. Decorative shrouds are prohibited unless the shroud is listed for use with that specific gas venting system and installed per the manufacturer's instructions ( § 802.6.1 (5) ) .
If my vent is 12 inches and 8 feet from a wall, which rule applies?
If the vent is 12 inches (300 mm) or less and located not less than 8 feet (2438 mm) from a vertical wall, use Figure 802.6.1 and Table 802.6.1 to determine roof termination height ( § 802.6.1 (1)(a) ) .
What if the vent passes through an insulated roof assembly?
Install an approved metal shield of at least 26‑gauge steel, extending not less than 2 inches above the insulation, secured per the manufacturer's instructions ( § 802.6.1.1 ) .
How do I reconcile multiple clearance requirements?
Calculate every clearance that applies (size‑/proximity‑based roof clearance, Type B/L or B‑W appliance clearances, forced‑air inlet clearance, etc.) and install the termination to meet the largest required clearance (see § 802.6.1 (1)–(3), (7) ) .
Are screws allowed to fasten double‑wall vent joints?
No — screws, rivets and similar fasteners must not penetrate the inner wall of double‑wall gas vents except at the permitted transition from the appliance draft hood/flue collar or single‑wall connector to a double‑wall vent ( § 802.6 (4) ) .
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