CMC · California Mechanical Code
What are the Type I (grease) duct construction, slope, access and cleaning rules?
For a homeowner: commercial kitchen grease ducts must be sloped so grease drains, have welded drains at low points, and include access openings large enough for cleaning or a 20×20 entry; factory-built ducts must be installed per the manufacturer’s listing.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
In plain English: Type I (grease) exhaust ducts must be installed and maintained so grease drains, can be inspected/cleaned, and meet any listing/manufacturer instructions for factory-built ducts. The key installation controls are minimum horizontal slope and required access/openings (personnel-entry sizes or cleaning openings) so ducts can be drained and cleaned. See the controlling rules: § 510.1.7, § 510.1.3, § 510.3, and § 510.3.3.
The most important point: grease ducts must be sloped and accessible so grease drains and people can clean them; factory-built/listed grease ducts must be installed exactly per their listing/manufacturer instructions. § 510.1.3 and § 510.1.7.
Requirements in detail
1) Scope and listing
- Type I (grease) exhaust ducts that are listed (factory-built) must be installed in accordance with the terms of their listing and the manufacturer’s instructions. See § 510.1.7.
- If a duct is factory-built/listed, certain installation details (joint types, slopes, access allowances) may be governed by the listing/manufacturer rather than a numeric slope or joint requirement in the Code. § 510.4 and § 510.4.1 also reference listed ducts and UL 1978.
2) Slope, drains, and no dips/traps
- All horizontal ducts must be installed with a minimum slope:
- ¼ inch per linear foot for horizontal runs up to 75 ft.
- 1 inch per linear foot for horizontal runs greater than 75 ft.
- Factory-built/listed grease ducts may be installed at a lesser slope if the listing/manufacturer permits. These slope rules are in § 510.1.3.
- Drains: Provide drains at low points in horizontal ducts. Drains must be continuously welded to the duct or installed per the listing/manufacturer. § 510.1.3.
- No dips or traps: Ducts shall be installed without forming dips or traps; in manifold systems the lowest end of the main must connect flush on the bottom with the branch. § 510.1.3.
3) Access/openings for inspection and cleaning
- General rule: provide openings at the side or top of the duct (whichever is more accessible) and at changes of direction. § 510.3.
- Exception: openings are NOT required where the portion of duct is accessible from the duct entry or discharge. § 510.3.
Key horizontal-duct specifics (personnel entry, cleaning intervals, platforms):
- Personnel entry opening: Horizontal grease ducts must provide at least one 20 in × 20 in (508 mm × 508 mm) opening sized for personnel entry. § 510.3.3.
- If a 20×20 opening is not possible: provide openings large enough to permit thorough cleaning at 12 ft (3658 mm) intervals. § 510.3.3.1.
- Safe access & work platform: If an opening is not easily reachable from a 10 ft (3048 mm) stepladder, safe access and a work platform must be provided. § 510.3.3.2.
- Support design for large ducts: Horizontal grease duct support systems for ducts 24 in (610 mm) and larger in any cross-section must be designed for the weight of ductwork plus 800 lb (362.9 kg) concentrated load at any point. § 510.3.3.3.
4) Access panel construction and marking
- Access panels must be of the same material and thickness as the duct, have a gasket/sealant rated to 1500°F (816°C), and be greasetight. Fasteners must be carbon or stainless steel and must not penetrate duct walls. § 510.3.6.
- For listed grease duct access door assemblies, install per the listing/manufacturer. § 510.3.6.1.
- A sign stating ACCESS PANEL – DO NOT OBSTRUCT is required on all access panels (see § 510.1.5).
Decision-relevant dimensions & values (table)
| Item | Value (imperial / metric) | Code Reference |
|---|---|---|
| Horizontal slope (≤ 75 ft run) | 1/4 in per ft (20.8 mm/m) | § 510.1.3 |
| Horizontal slope (> 75 ft run) | 1 in per ft (83.2 mm/m) | § 510.1.3 |
| Personnel-entry access opening | 20 in × 20 in (508 × 508 mm) | § 510.3.3 |
| Cleaning interval if 20×20 not possible | Openings at 12 ft intervals (3658 mm) | § 510.3.3.1 |
| Ladder reach threshold for platform | 10 ft stepladder (3048 mm) | § 510.3.3.2 |
| Large-duct support design load | Ducts ≥ 24 in: support for duct weight + 800 lb (362.9 kg) at any point | § 510.3.3.3 |
| Access-panel gasket rating | 1500°F (816°C); greasetight; same material/thickness as duct | § 510.3.6 |
| Drain requirement | Drains at low points; welded or per listing/manufacturer | § 510.1.3 |
| No dips/traps | Ducts shall be installed without dips or traps | § 510.1.3 |
Exceptions & special cases
- Factory-built/listed ducts: Where ducts are listed, the listing or manufacturer's instructions can override numeric slope or some joint/access requirements (i.e., allowed lesser slope or non-welded joints in UL‑listed products). Follow the listing language exactly. § 510.1.7, § 510.4, § 510.4.1.
- Accessible from entry/discharge: Openings are not required for duct portions that are already accessible from the duct entry or discharge point. § 510.3.
- Duct-to-hood connections: Certain duct-to-hood collar connections may be permitted without a continuous external weld per allowed figures/exceptions for listed systems — check § 510.5.3 and the listed-duct allowances.
- Ducts within enclosures: If duct access panels are inside a rated enclosure, the access panel assembly must have the same fire rating as the enclosure. § 510.3.6.2.
If you have a factory-built (listed) grease duct, the listing and installation manual may alter these provisions. Always check the listing and coordinate with the AHJ. § 510.1.7.
Common mistakes
- Installing horizontal ducts with insufficient slope (forgetting the change at 75 ft). Code requires ¼ in/ft ≤75 ft and 1 in/ft >75 ft, unless listing allows otherwise (§ 510.1.3).
- Omitting drains at duct low points or not welding drains to the duct where required (see § 510.1.3).
- Providing small cleaning ports too far apart instead of a personnel-entry opening or properly spaced cleaning openings (§ 510.3.3, § 510.3.3.1).
- Using access panels that are not greasetight, lack a 1500°F-rated gasket, or whose fasteners penetrate duct walls (violates § 510.3.6).
- Relying on non-listed installation practices for a listed (factory-built) duct — listed ducts must be installed per listing/manufacturer (§ 510.1.7, § 510.4).
Worked example — kitchen exhaust run applying the rules
Scenario: A restaurant has a horizontal grease duct run of 90 ft from the hood to a vertical riser. It's a field-fabricated (non‑listed) stainless duct.
Apply the code:
- Slope: Because the horizontal run is greater than 75 ft, you must slope at 1 in per ft. For 90 ft the total drop = 90 ft × 1 in/ft = 90 inches (7.5 ft). § 510.1.3.
- Drains: Provide a welded drain at the low point (coordinate location at the lowest point of the run). § 510.1.3.
- Openings: Because this is a horizontal duct, provide at least one 20 in × 20 in personnel-entry opening (or, if impossible, cleaning openings at 12 ft intervals). If entry is possible, put the 20×20 near a change of direction or the lowest accessible span so people can enter and clean. § 510.3.3, § 510.3.3.1.
- Access reach: If the chosen opening is not reachable from a 10 ft stepladder, provide a safe platform to that opening. § 510.3.3.2.
- Supports: If the cross-section of the duct is ≥ 24 in, design supports to carry duct weight plus 800 lb at any point. § 510.3.3.3.
- Access panel construction: Panels must be same material/thickness as duct, with a 1500°F-rated greasetight gasket, and fasteners that do not penetrate duct walls. § 510.3.6.
If instead the duct were a UL‑listed factory-built product, check the listing/manual — the manufacturer might allow a lesser slope and different joint/access details; install per § 510.1.7.
Related provisions (quick list)
- § 510.1.3 — Duct installation, slopes, drains, no dips/traps.
- § 510.1.7 — Type I (listed grease) ducts must follow listing/manufacturer.
- § 510.3 — Openings: location, general access rules, exceptions.
- § 510.3.3 — Horizontal ducts: 20×20 opening, 12 ft cleaning interval, platforms, supports.
- § 510.3.6 — Access panel construction (material, gasket rating, fasteners).
- § 510.4 / § 510.4.1 — Listed grease ducts and UL 1978 factory-built allowances.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 510.1.2 High relevance — show source text
510.1.2 Interconnection. Duct systems shall not be interconnected with any other building ventilation or exhaust system. [NFPA 96:7.1.3]
510.1.3 Duct Installation. All ducts shall be installed with a minimum slope of ¼ inch per linear foot (20.8 mm/m) on horizontal runs up to 75 feet (22 860 mm) and a minimum slope of 1 inch per linear foot (83.2 mm/m) on horizontal runs greater than 75 feet (22 860 mm). Factory-built grease ducts shall be permitted to be installed at a lesser slope in accordance with the listing and the manufacturer’s instructions. All horizontal ducts shall be provided with access in accordance with Section 510.3.3.
Drains shall be provided at low points in horizontal ducts. Where provided, drains shall be continuously welded to the exhaust duct or in accordance with the terms of the listing and the manufacturer’s installation manual.
All ducts shall be installed without forming dips or traps. In manifold (common duct) systems, the lowest end of the main duct shall be connected flush on the bottom with the branch duct. [NFPA 96:7.1.5 – 7.1.5.5]
510.1.4 Accessibility. Openings required for accessibility shall comply with Section 510.3 through Section 510.3.2. [NFPA 96:7.1.6]
510.1.5 Sign. A sign stating the following shall be placed on all access panels:
ACCESS PANEL – DO NOT OBSTRUCT [NFPA 96:7.1.7]
510.1.6 Bracing and Supports. Duct bracing and supports shall be of noncombustible material, securely attached to the structure and designed to carry gravity and lateral loads within the stress limitations of the building code. Bolts, screws, rivets, and other mechanical fasteners shall not penetrate duct walls.
510.1.7 Type I Exhaust Duct Systems. Listed grease ducts shall be installed in accordance with the terms of their listing and the manufacturer’s instructions. [NFPA 96:7.1.8]
510.1.8 Independent Grease Duct System. Single or combined Type I exhaust systems shall be independent of other exhaust systems.
510.2 Clearance. Clearance between ducts and combustible materials shall be provided in accordance with the requirements of Section 507.4 through Section 507.4.3.3. [NFPA 96:7.2] 510.3 Openings. Openings shall be provided at the sides or at the top of the duct, whichever is more accessible, and at changes of direction. Openings shall be protected by approved access constructed and installed in accordance with the requirements of Section 510.3.7. [NFPA 96:7.3.1, 7.3.2]
Exception: Openings shall not be required in portions of the duct that are accessible from the duct entry or discharge.
[NFPA 96:7.3.3]
510.3.1 Access Panel. For hoods with dampers in the exhaust or supply collar, an access panel for cleaning and inspection shall be provided in the duct or the hood within 18 inches (457 mm) of the damper. [NFPA 96:7.3.4]
Exception: Dampers that are accessible from under the hood.
CMC § 510.3.3 High relevance — show source text
510.3.3 Horizontal Ducts. On horizontal ducts, at least one 20 inch by 20 inch (508 mm by 508 mm) opening shall be provided for personnel entry. [NFPA 96:7.4.1.1] 510.3.3.1 Cleaning. Where an opening of the size specified in Section 510.3.3 is not possible, openings large enough to permit thorough cleaning shall be provided at 12 feet (3658 mm) intervals. [NFPA 96:7.4.1.2]
510.3.3.2 Safe Access and Work Platform. If not easily accessible from a 10 foot (3048 mm) stepladder, openings on horizontal grease duct systems shall be provided with safe access and a work platform. [NFPA 96:7.4.1.3]
510.3.3.3 Support. Support systems for horizontal grease duct systems 24 inches (610 mm) and larger in any cross-sectional dimension shall be designed for the weight of the ductwork plus 800 pounds (362.9 kg) at any point in the duct systems.
[NFPA 96:7.4.1.4]
510.3.4 Vertical Ducts. On vertical ductwork where personnel entry is possible, access shall be provided at the top of the vertical riser to accommodate descent.
[NFPA 96:7.4.2.1]
510.3.4.1 Access. Where personnel entry is not possible, adequate access for cleaning shall be provided on each floor. [NFPA 96:7.4.2.2]
510.3.4.2 Safe Access and Work Platform. If not easily accessible from the floor or a 10 foot
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(3048 mm) stepladder, openings on vertical grease ducts shall be provided with safe access and a work platform. [NFPA 96:7.4.2.3]
510.3.5 Nonlisted Ductwork. On nonlisted ductwork, the edge of the opening shall be not less than 1 [1] ⁄ 2 inches (38 mm) from all outside edges of the duct or welded seams. [NFPA 96:7.4.1.5]
510.3.6 Access Panels. Access panels shall be of the same material and thickness as the duct. Access panels shall have a gasket or sealant that is rated for 1500°F (816°C) and shall be greasetight. Fasteners, such as bolts, weld studs, latches, or wing nuts, used to secure the access panels shall be carbon steel or stainless steel and shall not penetrate duct walls. [NFPA 96:7.4.3.1 – 7.4.3.3]
510.3.6.1 Listed Grease Ducts. Listed grease duct access door assemblies (access panels) shall be installed in accordance with the terms of the listing and the manufacturer’s instructions. [NFPA 96:7.4.3.4]
CMC § 509.2.4.1 High relevance — show source text
509.2.4.1 Size and Pitch. Grease drip trays shall be kept to the minimum size needed to collect grease. Grease drip trays shall be pitched to drain into an enclosed metal container having a capacity not exceeding 1 gallon (4 L). [NFPA 96:6.2.4.2, 6.2.4.3]
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509.2.5 Grease Filter Orientation. Grease filters that require a specific orientation to drain grease shall be clearly so designated on the face of the filter as to be visible with the filter installed, or the hood or filter shall be constructed so that filters cannot be installed in the wrong orientation. [NFPA 96:6.2.5]
509.3 Solid-Fuel Grease Removal Devices. Where solid-fuel cooking equipment is provided with grease removal devices, these devices shall be in accordance with Section 517.0.
510.0 Exhaust Duct Systems.
510.1 General. Ducts shall not pass through fire walls.
[NFPA 96:7.1.1]
510.1.1 Fire Hazards. All ducts shall lead directly to the exterior of the building, so as not to unduly increase any fire hazard. [NFPA 96:7.1.2]
510.1.2 Interconnection. Duct systems shall not be interconnected with any other building ventilation or exhaust system. [NFPA 96:7.1.3]
510.1.3 Duct Installation. All ducts shall be installed with a minimum slope of ¼ inch per linear foot (20.8 mm/m) on horizontal runs up to 75 feet (22 860 mm) and a minimum slope of 1 inch per linear foot (83.2 mm/m) on horizontal runs greater than 75 feet (22 860 mm). Factory-built grease ducts shall be permitted to be installed at a lesser slope in accordance with the listing and the manufacturer’s instructions. All horizontal ducts shall be provided with access in accordance with Section 510.3.3.
Drains shall be provided at low points in horizontal ducts. Where provided, drains shall be continuously welded to the exhaust duct or in accordance with the terms of the listing and the manufacturer’s installation manual.
All ducts shall be installed without forming dips or traps. In manifold (common duct) systems, the lowest end of the main duct shall be connected flush on the bottom with the branch duct. [NFPA 96:7.1.5 – 7.1.5.5]
510.1.4 Accessibility. Openings required for accessibility shall comply with Section 510.3 through Section 510.3.2. [NFPA 96:7.1.6]
510.1.5 Sign. A sign stating the following shall be placed on all access panels:
ACCESS PANEL – DO NOT OBSTRUCT [NFPA 96:7.1.7]
CMC § 510.1.7 High relevance — show source text
510.1.7 Type I Exhaust Duct Systems. Listed grease ducts shall be installed in accordance with the terms of their listing and the manufacturer’s instructions. [NFPA 96:7.1.8]
510.1.8 Independent Grease Duct System. Single or combined Type I exhaust systems shall be independent of other exhaust systems.
510.2 Clearance. Clearance between ducts and combustible materials shall be provided in accordance with the requirements of Section 507.4 through Section 507.4.3.3. [NFPA 96:7.2] 510.3 Openings. Openings shall be provided at the sides or at the top of the duct, whichever is more accessible, and at changes of direction. Openings shall be protected by approved access constructed and installed in accordance with the requirements of Section 510.3.7. [NFPA 96:7.3.1, 7.3.2]
Exception: Openings shall not be required in portions of the duct that are accessible from the duct entry or discharge.
[NFPA 96:7.3.3]
510.3.1 Access Panel. For hoods with dampers in the exhaust or supply collar, an access panel for cleaning and inspection shall be provided in the duct or the hood within 18 inches (457 mm) of the damper. [NFPA 96:7.3.4]
Exception: Dampers that are accessible from under the hood.
510.3.2 Access for Cleaning and Inspection. Exhaust fans with ductwork connected to both sides shall have access for cleaning and inspection within 3 feet (914 mm) of each side of the fan. Wall-mounted exhaust fans shall have access for cleaning and inspection within 3 feet (914 mm) of the exhaust fan. [NFPA 96:7.3.8, 7.3.9]
510.3.3 Horizontal Ducts. On horizontal ducts, at least one 20 inch by 20 inch (508 mm by 508 mm) opening shall be provided for personnel entry. [NFPA 96:7.4.1.1] 510.3.3.1 Cleaning. Where an opening of the size specified in Section 510.3.3 is not possible, openings large enough to permit thorough cleaning shall be provided at 12 feet (3658 mm) intervals. [NFPA 96:7.4.1.2]
510.3.3.2 Safe Access and Work Platform. If not easily accessible from a 10 foot (3048 mm) stepladder, openings on horizontal grease duct systems shall be provided with safe access and a work platform. [NFPA 96:7.4.1.3]
510.3.3.3 Support. Support systems for horizontal grease duct systems 24 inches (610 mm) and larger in any cross-sectional dimension shall be designed for the weight of the ductwork plus 800 pounds (362.9 kg) at any point in the duct systems.
[NFPA 96:7.4.1.4]
510.3.4 Vertical Ducts. On vertical ductwork where personnel entry is possible, access shall be provided at the top of the vertical riser to accommodate descent.
[NFPA 96:7.4.2.1]
CMC § 510.3.4.2 High relevance — show source text
510.3.4.2 Safe Access and Work Platform. If not easily accessible from the floor or a 10 foot
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(3048 mm) stepladder, openings on vertical grease ducts shall be provided with safe access and a work platform. [NFPA 96:7.4.2.3]
510.3.5 Nonlisted Ductwork. On nonlisted ductwork, the edge of the opening shall be not less than 1 [1] ⁄ 2 inches (38 mm) from all outside edges of the duct or welded seams. [NFPA 96:7.4.1.5]
510.3.6 Access Panels. Access panels shall be of the same material and thickness as the duct. Access panels shall have a gasket or sealant that is rated for 1500°F (816°C) and shall be greasetight. Fasteners, such as bolts, weld studs, latches, or wing nuts, used to secure the access panels shall be carbon steel or stainless steel and shall not penetrate duct walls. [NFPA 96:7.4.3.1 – 7.4.3.3]
510.3.6.1 Listed Grease Ducts. Listed grease duct access door assemblies (access panels) shall be installed in accordance with the terms of the listing and the manufacturer’s instructions. [NFPA 96:7.4.3.4]
510.3.6.2 Within an Enclosure. Where openings are located in ducts within an enclosure, the access panel including its components shall be of the same fire rating as the enclosure.
510.3.7 Fire Protection System Devices. Openings for installation, servicing, and inspection of listed fire protection system devices and for duct cleaning shall be provided in ducts and enclosures and shall be in accordance with the requirements of Section 510.3 through Section 510.3.2 and Section 510.7.7.
Enclosure openings required to reach access panels in the ductwork shall be large enough for removal of the access panel through the enclosure opening. [NFPA 96:7.4.4.1 – 7.4.4.2]
510.4 Listed Grease Ducts. Listed grease ducts shall be installed in accordance with the terms of the listing and the manufacturer’s instructions. [NFPA 96:7.1.8]
510.4.1 Factory-Built Grease Ducts. Factory-built grease ducts in accordance with UL 1978 shall be permitted to incorporate non-welded joints in accordance with their listings.
510.5 Other Grease Ducts. Other grease ducts shall comply with the requirements of Section 510.5.1 through Section 510.5.5. [NFPA 96:7.5]
510.5.1 Materials. Ducts shall be constructed of and
supported by carbon steel not less than 0.060 of an inch (1.524 mm) (No. 16 MSG) in thickness or stainless steel not less than 0.048 of an inch (1.219 mm) (No. 18 MSG) in thickness. [NFPA 96:7.5.1.1]
CMC § 510.9.1.2 High relevance — show source text
tors. Listed vibration isolation connectors shall be permitted to be used on exterior roof locations where required for proper equipment vibration isolation. 510.9.1.2 Inspection and Cleaning. Fans shall be provided with safe access and a work surface for inspection and cleaning. [NFPA 96:7.8.2.2]
510.9.2 Wall Terminations. Wall terminations shall be arranged with or provided with the following properties: (1) The termination shall be through a noncombustible wall with a minimum of 10 feet (3048 mm) of clearance from the outlet to adjacent buildings, property lines, grade level, combustible construction, electrical equipment or lines, and with the closest point of any air intake or operable door or window at or below the plane of the exhaust termination. The closest point of any air intake or operable door or window above the plane of the exhaust termination shall be a minimum of 10 feet (3048 mm) in distance, plus 3 inches (76 mm) for each 1 degree (0.017 rad) from horizontal, the angle of degree being measured from the center of the exhaust termination to the center of the air intake or operable door or window, as indicated in Figure 510.9.2. Exception: A wall termination in a secured area shall be permitted to be at a lower height above grade if acceptable to the Authority Having Jurisdiction. (2) The exhaust flow shall be directed perpendicularly outward from the wall face or upward. (3) All the ductwork shall be pitched to drain the grease back into the hood(s) or with a drain provided to bring the grease back into a container within the building or into a remote grease trap. (4) A listed grease duct shall comply with Section 510.3.3 through Section 510.3.7; other ducts shall comply with Section 510.5.
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(5) An approved fan shall meet the requirements of Section 510.9.2(3), and Section 511.1.1 or Section 511.1.3. [NFPA 96:7.8.3] 510.10 Solid-Fuel Duct Systems. Where solid-fuel cooking equipment is to be vented, the duct system shall be in accordance with Section 517.0.
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm
Notes:
Fresh air intake (FAI) applies to an air intake, including an operable door or window.
Example: (a) FAIs 1 and 5 are on the same plane of exhaust or lower: 10 feet (3048 mm) min. between closest edges. (b) FAIs 2, 3, and 4 are above plane of exhaust fan: 10 feet + 0.25 feet (3048 mm + 76 mm) per degree between closest edges.
FIGURE 510.9.2
EXHAUST TERMINATION DISTANCE FROM FRESH AIR INTAKE (FAI) OR OPERABLE DOOR OR WINDOW
[NFPA 96: FIGURE 7.8.3]
511.0 Air Movement.
CMC § 603.2 High relevance — show source text
In under floor or crawl spaces. . . . . . . . . . . . . . . . 603.2
Inspection and cleaning of . . . . . . . . . . . 514.2, 514.4.2
Insulation of . . . . . . . . . . . . . . . . . . 605.0, 605.2, 605.3,
E 502.4.1, E 503.4.7.1,
Table E 503.7.2–Table E 503.7.3(2)
Joints and seams . . . . . . . . . . . . . . . . . . . . . . . . . 603.9
Leakage test . . . . . . . . . . . . . . . . . . . 603.9.2 , 603.9.2.1
Manifold (common duct) . . . . . . . . . . . . . . . . . . . . 511.4
Material of . . . . . . . . . . . . . . . . . . 506.1, 510.5.1, 602.0
Metal . . . . . . . . . . . . . . . . . 506.1, 602.5, 603.3, 603.7.1
Non-grease type. . . . . . . . . . . . . . . . . . . . . 519.4, 519.5
Nonmetallic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.5
Openings. . . . . . . . . . . . . . . . 510.3, 510.3.3–510.3.3.2,
510.3.4.2, 511.1.5
Other grease . . . . . . . . . . . . . . . . . . . . . . 510.5, 602.5.4
Plastic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.5
Product-conveying . . . . . . . . . . . . . . . . . 206.0, 502.2.2,
506.0, Table 506.2(1),
Table 506.2(2)
Protection of. . . . . . . . . . . . . . . . . . . . . . . . 506.9, 603.6
Return duct sizing . . . . . . . . . . . . . . . . . . . . . . . 601.2.1
Smoke Detectors . . . . . . . . . . . . . . . . . . . . . . . . 609.1.1
Solid-fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517.0
Support systems . . . . . . . . . . .504.4.5, 506.7–506.8.4,
510.1.6, 510.1.7, 510.3.3.3,
510.5.1, 603.3, 603.7
CMC § 510.7.6 Medium relevance — show source text
510.7.6 Listed. For listed grease ducts, see Section 510.4.
510.7.7 Fire Doors. Where openings in the enclosure walls are provided, they shall be protected by listed fire doors of proper rating. Fire doors shall be installed in accordance with NFPA 80. Openings on other listed materials or products shall be clearly identified and labeled according to the terms of the listing and the manufacturer’s instructions and shall be acceptable to the Authority Having Jurisdiction. [NFPA 96:7.7.4.1 – 7.7.4.3] The fire door shall be readily accessible, aligned, and of sufficient size to allow access to the rated access
panels on the ductwork. [NFPA 96:7.7.4.4]
510.7.8 Ducts with Enclosure(s). Each duct system shall constitute an individual system serving only exhaust hoods in one fire zone on one floor. Multiple ducts shall not be permitted in a single enclosure unless acceptable to the Authority Having Jurisdiction. [NFPA 96:7.7.5.1 – 7.7.5.2]
510.8 Underground Installations. Grease ducts installed underground shall be approved for underground installation. The material of the grease duct shall be corrosion-resistant and shall comply with Section 510.5.1.
510.8.1 Grease Receptacle. The grease duct shall be sloped to drain the grease back to an approved grease collection device. A grease collection device shall be located at the base of the vertical riser.
510.8.2 Cleanouts. For horizontal installations, cleanouts for cleaning and maintenance shall be provided
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on the top portion of the grease duct in accordance with Section 510.3 and shall be labeled at the interior portion of the duct.
510.9 Termination of Type I Hood Exhaust System. The exhaust system shall terminate as follows:
(1) Outside the building with a fan or duct.
(2) Through the roof or to the roof from outside, as in Section 510.9.1, or through a wall, as in Section 510.9.2. [NFPA 96:7.8.1] 510.9.1 Rooftop Terminations. Rooftop terminations shall be arranged with or provided with the following:
(1) A minimum of 10 feet (3048 mm) of horizontal clearance from the outlet to adjacent buildings, property lines, and air intakes.
(2) A minimum of 5 feet (1524 mm) of horizontal clearance from the outlet (fan housing) to any combustible structure.
(3) A vertical separation of 3 feet (914 mm) above any air intakes within 10 feet (3048 mm) of the exhaust outlet.
(4) The ability to drain grease out of any traps or low points formed in the fan or duct near the termination of the system into a collection container that is noncombustible, closed, rainproof, and structurally sound for the service to which it is applied and that will not sustain combustion.
(5) A grease collection device that is applied to exhaust systems that does not inhibit the performance of any fan.
CMC § 206.0 Medium relevance — show source text
Environmental air. . . . . . . . . . . . . . . . . . . . 206.0, 504.0
Exhaust, commercial kitchen . . . . . . . . . . . . . . . . 510.0
Existing metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.2
Factory-made air. . . . . . . . . . . . . 603.4, 603.4.1, 603.7
Fire protection required . . . . . . . . . . . . . . . . . . . . . 506.8
Flexible air ducts and connectors. . . . . . . . . . . . . . 603.4,
603.4.1.1, 603.7.2
For kilns . . . . . . . . . . . . . . . . . 603.13.6, 930.5.3, 930.6
Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . 206.0, 905.0
Gravity ventilation . . . . . . . . . . . . . . . . . . . . . . . 930.5.3
Grease type . . . . . . . . . . . . . . . . . . . . . . . . 206.0, 510.0
Gypsum wallboard . . . . . . . . . . . . . . . . . . . . . . . 602.5.2
In under floor or crawl spaces. . . . . . . . . . . . . . . . 603.2
Inspection and cleaning of . . . . . . . . . . . 514.2, 514.4.2
Insulation of . . . . . . . . . . . . . . . . . . 605.0, 605.2, 605.3,
E 502.4.1, E 503.4.7.1,
Table E 503.7.2–Table E 503.7.3(2)
Joints and seams . . . . . . . . . . . . . . . . . . . . . . . . . 603.9
Leakage test . . . . . . . . . . . . . . . . . . . 603.9.2 , 603.9.2.1
Manifold (common duct) . . . . . . . . . . . . . . . . . . . . 511.4
Material of . . . . . . . . . . . . . . . . . . 506.1, 510.5.1, 602.0
Metal . . . . . . . . . . . . . . . . . 506.1, 602.5, 603.3, 603.7.1
Non-grease type. . . . . . . . . . . . . . . . . . . . . 519.4, 519.5
Nonmetallic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.5
CMC § 1012.5.1 Medium relevance — show source text
[BE] 1012.5.1 Width and capacity. The minimum width and required capacity of a means of egress ramp shall be not less than that required for corridors by Section 1020.3. The clear width of a ramp between handrails, if provided, or other permissible projections shall be 36 inches (914 mm) minimum.
[BE] 1012.5.2 Headroom. The minimum headroom in all parts of the means of egress ramp shall be not less than 80 inches (2032 mm) above the finished floor of the ramp run and any intermediate landings. The minimum clearance shall be maintained for the full width of the ramp and landing.
[BE] 1012.5.3 Restrictions. Means of egress ramps shall not reduce in width in the direction of egress travel. Projections into the required ramp and landing width are prohibited. Doors opening onto a landing shall not reduce the clear width to less than 42 inches (1067 mm).
[BE] 1012.6 Landings. Ramps shall have landings at the bottom and top of each ramp, points of turning, entrance, exits and at doors. Landings shall comply with Sections 1012.6.1 through 1012.6.5.
[BE] 1012.6.1 Slope. Landings shall have a slope not steeper than 1 unit vertical in 48 units horizontal (2-percent slope) in any direction. Changes in level are not permitted.
[BE] 1012.6.2 Width. The landing width shall be not less than the width of the widest ramp run adjoining the landing.
10-34 2025 CALIFORNIA FIRE CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MEANS OF EGRESS
[BE] 1012.6.3 Length. The landing length shall be 60 inches (1525 mm) minimum.
Exceptions:
In Group R-2 and R-3 individual dwelling and sleeping units that are not required to be Accessible units, Type A units or Type B units in accordance with Chapter 11A or 11B of the California Building Code, landings are permitted to be 36 inches (914 mm) minimum.
Where the ramp is not a part of an accessible route, the length of the landing shall not be required to be more than 48 inches (1219 mm) in the direction of travel.
[BE] 1012.6.4 Change in direction. Where changes in direction of travel occur at landings provided between ramp runs, the landing shall be 60 inches by 60 inches (1524 mm by 1524 mm) minimum.
Exception: In Group R-2 and R-3 individual dwelling or sleeping units that are not required to be Accessible units, Type A units or Type B units in accordance with Section 1108 of the California Building Code, landings are permitted to be 36 inches by 36 inches (914 mm by 914 mm) minimum.
[BE] 1012.6.5 Doorways. Where doorways are located adjacent to a ramp landing, maneuvering clearances required by ICC A117.1 are permitted to overlap the required landing area.
[BE] 1012.7 Ramp construction. Ramps shall be built of materials consistent with the types permitted for the type of construction of the building, except that wood handrails shall be permitted for all types of construction.
CMC § 510.3.7 Medium relevance — show source text
510.3.7 Fire Protection System Devices. Openings for installation, servicing, and inspection of listed fire protection system devices and for duct cleaning shall be provided in ducts and enclosures and shall be in accordance with the requirements of Section 510.3 through Section 510.3.2 and Section 510.7.7.
Enclosure openings required to reach access panels in the ductwork shall be large enough for removal of the access panel through the enclosure opening. [NFPA 96:7.4.4.1 – 7.4.4.2]
510.4 Listed Grease Ducts. Listed grease ducts shall be installed in accordance with the terms of the listing and the manufacturer’s instructions. [NFPA 96:7.1.8]
510.4.1 Factory-Built Grease Ducts. Factory-built grease ducts in accordance with UL 1978 shall be permitted to incorporate non-welded joints in accordance with their listings.
510.5 Other Grease Ducts. Other grease ducts shall comply with the requirements of Section 510.5.1 through Section 510.5.5. [NFPA 96:7.5]
510.5.1 Materials. Ducts shall be constructed of and
supported by carbon steel not less than 0.060 of an inch (1.524 mm) (No. 16 MSG) in thickness or stainless steel not less than 0.048 of an inch (1.219 mm) (No. 18 MSG) in thickness. [NFPA 96:7.5.1.1]
510.5.2 Factory-Built Grease Ducts. Factory-built grease ducts listed in accordance with UL 1978 shall be permitted to use materials in accordance with their listing. {NFPA 96:7.5.1.2}
510.5.3 Installation. All seams, joints, penetrations, and duct-to-hood collar connections shall have a liquidtight continuous external weld. [NFPA 96:7.5.2.1]
Exceptions:
(1) Factory-built grease ducts listed in accordance with UL 1978 shall be permitted to incorporate nonwelded joint construction in accordance with their listings. {NFPA 96:7.5.2.1.1}
(2) Duct-to-hood collar connections as shown in Figure 510.5.3 shall not require a liquidtight continuous external weld. [NFPA 96:7.5.2.2]
(3) Penetrations shall be permitted to be sealed by other listed devices that are tested to be greasetight and are evaluated under the same conditions of fire severity as the hood or enclosure of listed grease extractors and whose presence does not detract from the hood’s or duct’s structural integrity. [NFPA 96:7.5.2.3]
(4) Internal welding shall be permitted, provided the joint is formed or ground smooth and is readily accessible for inspection. [NFPA 96:7.5.2.4]
For SI units: 1 inch = 25.4 mm, °C = (°F-32)/1.8
FIGURE 510.5.3
PERMITTED DUCT-TO HOOD COLLAR CONNECTION
[NFPA 96: FIGURE 7.5.2.2]
CMC § 12.6.1.1.4 Medium relevance — show source text
[NFPA 96:12.6.1.1.4] 514.4.2 Removal of Contaminants. Hoods, grease removal devices, fans, ducts, and other appurtenances shall be cleaned to remove combustible contaminants prior to surfaces becoming heavily contaminated with grease or oily sludge. [NFPA 96:12.6.2] 514.4.3 Electrical Switches. At the start of the cleaning process, electrical switches that could be activated accidentally shall be locked out. [NFPA 96:12.6.3] 514.4.4 Fire Suppression System. Components of the fire suppression system shall not be rendered inoperable during the cleaning process. [NFPA 96:12.6.4] 514.4.5 Inoperable. Fire-extinguishing systems shall be permitted to be rendered inoperable during the cleaning process where serviced by properly trained and qualified persons. [NFPA 96:12.6.5] 514.4.6 Solvents/Cleaning Aids. Flammable solvents or other flammable cleaning aids shall not be used. [NFPA 96:12.6.6] 514.4.7 Cleaning Chemicals. Cleaning chemicals shall not be applied on fusible links or other detection devices of the automatic extinguishing system. [NFPA 96:12.6.7] 514.4.8 Coating. After the exhaust system is cleaned, it shall not be coated with powder or other substance. [NFPA 96:12.6.8]
514.4.9 Access Panels and Cover Plates. When cleaning procedures are completed, all access panels (doors) and cover plates shall be restored to their normal operational condition. [NFPA 96:12.6.9]
514.4.10 Date of Inspection. When an access panel is removed, a service company label or tag preprinted with the name of the company and giving the date of inspection or cleaning shall be affixed near the affected access panels.
[NFPA 96:12.6.10]
514.4.11 Airflow. Dampers and diffusers shall be positioned for proper airflow. [NFPA 96:12.6.11] 514.4.12 Operable State. When cleaning procedures are completed, all electrical switches and system components shall be returned to an operable state. [NFPA 96:12.6.12]
514.4.13 Certification of Service. When an exhaust system is inspected or cleaned, a certificate showing the name of the servicing company, the name of the person performing the work, and the date of inspection or cleaning shall be maintained on the premises. [NFPA 96:12.6.13]
514.4.14 Report Provided. After cleaning or inspection is completed, the exhaust cleaning company and the person performing the work at the location shall provide the owner of the system with a written report that also specifies areas that were inaccessible or not cleaned. [NFPA 96:12.6.14]
514.4.15 Unclean Area. Where required, certificates of inspection and cleaning and reports of areas not cleaned shall be submitted to the Authority Having Jurisdiction.
[NFPA 96:12.6.15]
Frequently asked questions
Who decides if a factory-built grease duct can use a lesser slope than the Code?
The manufacturer’s listing and installation manual govern any permitted lesser slope for a listed (factory-built) grease duct; install per the listing. See § 510.1.7 and § 510.4.
Is a 20×20 opening always required on horizontal ducts?
Yes for personnel entry on horizontal grease ducts — at least one 20 in × 20 in opening is required; if that size isn't possible, provide cleaning openings large enough to permit thorough cleaning at 12 ft intervals. § 510.3.3 and § 510.3.3.1.
Where must drains be located and how must they be attached?
Drains are required at low points in horizontal ducts and shall be continuously welded to the exhaust duct or installed per the listing/manufacturer’s instructions. § 510.1.3.
What if I can't reach an access opening with a stepladder?
If an opening on a horizontal grease duct is not easily accessible from a 10 ft (3048 mm) stepladder, you must provide safe access and a work platform to reach it. § 510.3.3.2.
Do access panel fasteners or seals have special requirements?
Yes. Access panels must be same material/thickness as the duct, greasetight, use a gasket/sealant rated 1500°F (816°C), and fasteners must not penetrate duct walls (use carbon or stainless fasteners as directed). § 510.3.6.
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