Page 68 - 2018_IMC

EXHAUST SYSTEMS

SECTION 505 exhaust air rate. Such makeup air systems shall be equipped
DOMESTIC COOKING EXHAUST EQUIPMENT with a means of closure and shall be automatically controlled
505.1 General. Domestic cooking exhaust equipment shall to start and operate simultaneously with the exhaust system.
comply with the requirements of this section. 505.5 Common exhaust systems for domestic kitchens
505.2 Domestic cooking exhaust. Where domestic cooking located in multistory structures. Where a common multi-
exhaust equipment is provided, it shall comply with the fol- story duct system is designed and installed to convey exhaust
lowing as applicable: from multiple domestic kitchen exhaust systems, the con-
struction of the system shall be in accordance with all of the
1. The fan for overhead range hoods and downdraft following:
exhaust equipment not integral with the cooking appli-
ance shall be listed and labeled in accordance with UL 1. The shaft in which the duct is installed shall be con-
507. structed and fire-resistance rated as required by the
International Building Code.
2. Overhead range hoods and downdraft exhaust equip-
ment with integral fans shall comply with UL 507. 2. Dampers shall be prohibited in the exhaust duct,
except as specified in Section 505.3. Penetrations of
3. Domestic cooking appliances with integral downdraft the shaft and ductwork shall be protected in accor-
exhaust equipment shall be listed and labeled in accor- dance with Section 607.5.5, Exception 2.
dance with UL 858 or ANSI Z21.1.
3. Rigid metal ductwork shall be installed within the
4. Microwave ovens with integral exhaust for installation shaft to convey the exhaust. The ductwork shall be
over the cooking surface shall be listed and labeled in constructed of sheet steel having a minimum thick-
accordance with UL 923.
ness of 0.0187 inch (0.4712 mm) (No. 26 gage) and in
505.3 Exhaust ducts. Domestic cooking exhaust equipment accordance with SMACNA Duct Construction Stand-
shall discharge to the outdoors through sheet metal ducts con- ards.
structed of galvanized steel, stainless steel, aluminum or cop- 4. The ductwork within the shaft shall be designed and
per. Such ducts shall have smooth inner walls, shall be air installed without offsets.
tight, shall be equipped with a backdraft damper, and shall be
independent of all other exhaust systems. Installations in 5. The exhaust fan motor design shall be in accordance
Group I-1 and I-2 occupancies shall be in accordance with the with Section 503.2.
International Building Code and Section 904.13 of the Inter- 6. The exhaust fan motor shall be located outside of the
national Fire Code. airstream.
Exceptions: 7. The exhaust fan shall run continuously, and shall be
connected to a standby power source.
1. In other than Groups I-1 and I-2, where installed in
accordance with the manufacturer’s instructions and 8. Exhaust fan operation shall be monitored in an
where mechanical or natural ventilation is otherwise approved location and shall initiate an audible or
provided in accordance with Chapter 4, listed and visual signal when the fan is not in operation.
labeled ductless range hoods shall not be required to 9. Where the exhaust rate for an individual kitchen
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discharge to the outdoors. exceeds 400 cfm (0.19 m /s) makeup air shall be pro-
2. Ducts for domestic kitchen cooking appliances vided in accordance with Section 505.4.
equipped with downdraft exhaust systems shall be 10. A cleanout opening shall be located at the base of the
permitted to be constructed of Schedule 40 PVC shaft to provide access to the duct to allow for clea-
pipe and fittings provided that the installation com- nout and inspection. The finished openings shall be
plies with all of the following: not less than 12 inches by 12 inches (305 mm by 305
mm).
2.1. The duct shall be installed under a concrete
slab poured on grade. 11. Screens shall not be installed at the termination.
2.2. The underfloor trench in which the duct is 12. The common multistory duct system shall serve only
installed shall be completely backfilled with kitchen exhaust and shall be independent of other
sand or gravel. exhaust systems.
2.3. The PVC duct shall extend not more than 1 505.6 Other than Group R. In other than Group R occupan-
inch (25 mm) above the indoor concrete cies, where domestic cooktops, ranges, and open-top broilers
floor surface. are used for domestic purposes, domestic cooking exhaust
systems shall be provided.
2.4. The PVC duct shall extend not more than 1
inch (25 mm) above grade outside of the
building. SECTION 506
2.5. The PVC ducts shall be solvent cemented. COMMERCIAL KITCHEN HOOD VENTILATION
505.4 Makeup air required. Exhaust hood systems capable SYSTEM DUCTS AND EXHAUST EQUIPMENT
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of exhausting in excess of 400 cfm (0.19 m /s) shall be pro- 506.1 General. Commercial kitchen hood ventilation ducts
vided with makeup air at a rate approximately equal to the and exhaust equipment shall comply with the requirements of

2018 INTERNATIONAL MECHANICAL CODE  51
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