Page 73 - 2018_IMC

EXHAUST SYSTEMS

fan components. Such rooms or spaces shall be venti- water splash or carryover can occur in the transi-
lated in accordance with the fan manufacturer’s instal- tion duct as a result of a washing operation, the
lation instructions. transition duct shall slope downward toward the
cabinet drain pan for a length not less than 18
506.5.2 Pollution-control units. The installation of pollu-
tion-control units shall be in accordance with the manufac- inches (457 mm). Ducts shall transition to the full
turer’s installation instructions and all of the following: size of the unit’s inlet and outlet openings.
14. Extra-heavy-duty appliance exhaust systems shall
1. Pollution-control units shall be listed and labeled
in accordance with UL 1978. not be connected to pollution-control units except
where such units are specifically designed and
2. Fans serving pollution-control units shall be listed listed for use with solid fuels.
and labeled in accordance with UL 762.
15. Pollution-control units shall be maintained in
3. Pollution-control units shall be mounted and accordance with the manufacturer’s instructions.
secured in accordance with the manufacturer’s
installation instructions and the International 506.5.3 Exhaust fan discharge. Exhaust fans shall be
Building Code. positioned so that the discharge will not impinge on the
roof, other equipment or appliances or parts of the struc-
4. Pollution-control units located indoors shall be ture. A vertical discharge fan shall be manufactured with
listed and labeled for such use. Where enclosed an approved drain outlet at the lowest point of the housing
duct systems, as required by Section 506.3.11, are to permit drainage of grease to an approved grease reser-
connected to a pollution control unit, such unit voir.
shall be located in a room or space having the 506.5.4 Exhaust fan mounting. Up-blast fans serving
same fire-resistance rating as the duct enclosure. Type I hoods and installed in a vertical or horizontal posi-
Access shall be provided for servicing and clean- tion shall be hinged, supplied with a flexible weatherproof
ing of the unit. The space or enclosure shall be electrical cable to permit inspection and cleaning and shall
ventilated in accordance with the manufacturer’s be equipped with a means of restraint to limit the swing of
installation instructions.
the fan on its hinge. The ductwork shall extend not less
5. A clearance of not less than 18 inches (457 mm) than 18 inches (457 mm) above the roof surface.
shall be maintained between the pollution-control 506.5.5 Clearances. Exhaust equipment serving a Type I
unit and combustible material. hood shall have a clearance to combustible construction of
6. Roof-mounted pollution-control units shall be not less than 18 inches (457 mm).
listed for outdoor installation and shall be mounted Exception: Factory-built exhaust equipment installed
not less than 18 inches (457 mm) above the roof. in accordance with Section 304.1 and listed for a lesser
7. Exhaust outlets for pollution-control units shall be clearance.
in accordance with Section 506.3.13. 506.5.6 Termination location. The outlet of exhaust
8. An airflow differential pressure control shall be equipment serving Type I hoods shall be in accordance
provided to monitor the pressure drop across the with Section 506.3.13.
filter sections of a pollution-control unit. When the Exception: The minimum horizontal distance between
airflow is reduced below the design velocity, the vertical discharge fans and parapet-type building struc-
airflow differential pressure control shall activate tures shall be 2 feet (610 mm) provided that such struc-
a visual alarm located in the area where cooking tures are not higher than the top of the fan discharge
operations occur. opening.
9. Pollution-control units shall be provided with a
factory-installed fire suppression system.
SECTION 507
10. Service space shall be provided in accordance with COMMERCIAL KITCHEN HOODS
the manufacturer’s instructions for the pollution-
control unit and the requirements of Section 306. 507.1 General. Commercial kitchen exhaust hoods shall
comply with the requirements of this section. Hoods shall be
11. Wash-down drains shall discharge through a Type I or II and shall be designed to capture and confine
grease interceptor and shall be sized for the flow. cooking vapors and residues. A Type I or Type II hood shall
Drains, shall be sealed with a trap or other be installed at or above appliances in accordance with Sec-
approved means to prevent air bypass. Where a tions 507.2 and 507.3. Where any cooking appliance under a
trap is utilized it shall have a seal depth that single hood requires a Type I hood, a Type I hood shall be
accounts for the system pressurization and evapo- installed. Where a Type II hood is required, a Type I or Type
ration between cleanings. II hood shall be installed. Where a Type I hood is installed,
the installation of the entire system, including the hood,
12. Protection from freezing shall be provided for the ducts, exhaust equipment and makeup air system shall com-
water supply and fire suppression systems where ply with the requirements of Sections 506, 507, 508 and 509.
such systems are subject to freezing. Exceptions:
13. Duct connections to pollution-control units shall 1. Factory-built commercial exhaust hoods that are
be in accordance with Section 506.3.2.3. Where listed and labeled in accordance with UL 710, and

56 2018 INTERNATIONAL MECHANICAL CODE 
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