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. Seams, joints, penetrations, and duct-to-hood collar connections shall have a liquid-tight continuous external weld. [NFPA 96:7.5.2.1] Exceptions: (1) Factory-built grease duct listed in accordance with

UL 1978 shall be permitted to incorporate non

Factory-built grease duct listed in accordance with

UL 1978 shall be permitted to incorporate nonwelded joint construction in accordance with their listing. [NFPA 96:7.5.2.1.1]

2019 CALIFORNIA MECHANICAL CODE 101

EXHAUST SYSTEMS any other purpose or distributed to any other persons or parti es.

(2) Duct-to-hood collar connections as shown in Figure

510.5.3 shall not require a liquid-tight continuous

(2) Duct-to-hood collar connections as shown in Figure

510.5.3 shall not require a liquid-tight 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

(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 or the 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

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 a 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. Duct-toduct connection shall be as follows: (1) Telescoping joint, as shown in Figure

510.5.3.2(1).

(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).

(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]

ceiling assembly is required to have a fire resistance rating, the ducts shall be enclosed in a continuous enclosure extending from the lowest fire-rated ceiling or floor above the hood, through concealed spaces, to or through the roof, to maintain the integrity of the fire separations required by the applicable building code provisions. The enclosure shall be sealed around the duct at the point of penetration of the first firerated barrier after the hood, to maintain the fire resistance rating of the enclosure. The enclosure shall be vented to the exterior of the building through weather-protected openings.

[NFPA 96:7.7.1.2 – 7.7.1.4] Exception: The continuous enclosure provisions shall not be required where a field-applied grease duct enclosure or a factory-built grease duct enclosure (see Section 507.4.4 through Section 507.4.6) is protected with a listed duct-through-penetration protection system equivalent to the fire resistance rating of the assembly being penetrated, and where the materials are installed in accordance with the conditions of the listings and the manufacturer’s installation instructions and are acceptable to the Authority Having Jurisdiction. [NFPA 96:7.7.1.5] 510.7.1 Less than Four Stories. Buildings less than four stories in height shall have an enclosure with a fire resistance rating of not less than 1 hour. [NFPA 96:7.7.2.1.1] 510.7.2 Four Stories or More. Buildings four stories or more in height shall have an enclosure with a fire resistance rating of not less than 2 hours. [NFPA 96:7.7.2.1.2] 510.7.3 Clearance. Clearance from the duct or the exhaust fan to the interior surface of enclosures of combustible construction shall be not less than 18 inches (457 mm), and clearance from the duct to the interior surface of enclosures of noncombustible or limited-combustible construction shall be not less than 6 inches (152 mm). Provisions for reducing clearances as described in Section 507.4 through Section 507.4.3.3 shall not be applicable to enclosures. [NFPA 96:7.7.2.2.1 – 7.7.2.2.3] Exception: Clearance from the outer surfaces of fieldapplied grease duct enclosures and factory-built grease duct enclosures to the interior surfaces of construction installed around them shall be permitted to be reduced where the field-applied grease duct enclosure materials and the factory-built grease duct enclosures are installed in accordance with the conditions of the listings and the manufacturer’s installation instructions and are acceptable to the Authority Having Jurisdiction. [NFPA 96:7.7.2.2.4] 510.7.4 Mechanical and Structural Integrity. Fieldapplied grease duct enclosures and factory-built grease duct enclosures shall provide mechanical and structural integrity, resiliency, and stability where subjected to expected building environmental conditions, duct movement under general operating conditions, and duct movement as a result of interior and exterior fire conditions.

[NFPA 96:7.7.2.2.5]

(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] For telescoping and bell-type connections, the inside duct 510.5.5 Telescoping and Bell-Type Connections. section shall be uphill of the outside duct section. [NFPA 96:7.5.5.3] 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.