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] 510.5.3.1 Duct Leakage Test. Prior to the use of or concealment of any portion of a grease duct system, a leakage test shall be performed to determine that all welded joints and seams are liquid tight.

[NFPA 96:7.5.2.1.2] 510.5.3.2 Welded Duct Connection. Acceptable duct-to-duct connection shall be as follows:

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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 (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

2022 CALIFORNIA MECHANICAL CODE 103

EXHAUST SYSTEMS

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]

For SI units: 1 inch = 25.4 mm

Notes:

Duct size decreases (going upward) with each telescope.
Smaller (inside) duct section shall be above or uphill (on sloped duct), to be self draining into larger (outside) duct.

FIGURE 510.5.3.2(1) TELESCOPING -TYPE DUCT CONNECTION

[NFPA 96: FIGURE 7.5.5.1(a)]

Notes:

Duct size stays the same throughout the duct system.
Smaller (inside) male duct end is always above or uphill (on sloped duct), to be self draining into larger (outside) female duct end.

FIGURE 510.5.3.2(2) BELL-TYPE DUCT CONNECTION

[NFPA 96: FIGURE 7.5.5.1(b)]

FIGURE 510.5.3.2(3) FLANGE WITH EDGE WELD DUCT CONNECTION

[NFPA 96: FIGURE 7.5.5.1(c)]

FIGURE 510.5.3.2(4) FLANGE WITH FILLED WELD DUCT CONNECTION

[NFPA 96: FIGURE 7.5.5.1(d)]

104 2022 CALIFORNIA MECHANICAL CODE

(1) Telescoping joint, as shown in Figure

510.5.3.2(1). (2) Bell-type joint, as shown in Figure 510.5.3.2(2). (3) Flange with edge weld, as shown in Figure

510.5.3.2(3). (4) Flange with filled weld, as shown in Figure

510.5.3.2(4). [NFPA 96:7.5.5.1] 510.5.4 Butt Welded Connections. Butt welded connections shall not be permitted. [NFPA 96:7.5.5.2] 510.5.5 Telescoping and Bell-Type Connections. For telescoping and bell-type connections, the inside duct section shall always be uphill of the outside duct section.

[NFPA 96:7.5.5.3] The overlap shall not exceed 2 inches (51 mm) as shown in Figure 510.5.3.2(1). 510.5.6 Duct Leakage Test. Prior to the use of or concealment of a grease duct system, a leakage test shall be performed to determine that welded joints and seams are liquid tight. The leakage test shall consist of a light test, water pressure test, or an approved equivalent test. The permit holder shall be responsible for providing the necessary equipment and for performing the test. Such test shall be conducted in accordance with ASHRAE 154.