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NFPA 96 and Building Code Requirements
for Commercial Kitchen Hood Systems
Presentation for the Sevier County Fire Code and
Building Code Officials
Presented by Roger Griffith, PE
Griffith Engineering, Jefferson City, TN
April 21, 2004
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Course Outline
Problem Areas
General Requirements
Hoods Exhaust Ducts
Fans
Fire Suppression System
Code Changes NFPA 96
International Mechanical Code (IMC)
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GENERAL REQUIREMENTS
Where are commercial hoods required?
NFPA 96: Cooking equipment used in processes
producing smoke and grease-laden vapors shallbe equipped with
NFPA 96 A-1-1 intended to includeresidential cooking equipment where used forpurposes other than residential family use
SMC gives exceptions for domestic equipmentinstalled in dwelling units and ovens do not heatfood above 2120F.
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Clearances
18 inches to combustible material
3 inches to limited-combustible material
0 inches to noncombustible material
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Exceptions
When the hood is listed for lesser clearances
If the combustible materialis protected asfollows:
28 gage sheet metal spaced out 1 inch onnoncombustible spacers 9 inch clearance tocombustible material
22 gage sheet metal on 1 inch mineral wool bats orceramic fiber blanket reinforced with wire mesh or
equivalent spaced out 1 inch on noncombustible spacers 3 inch clearance to combustible material
Reduced clearance to limited-combustible materials tozero clearance where protected by noncombustiblematerials or materials listed for the purpose of reducingclearance, and acceptable to the AHJ.
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9 inch clearance reduction
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3 inch clearance reduction
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Clearances
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Clearances
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Duct Clearances
Protection methods for ducts to reduceclearances shall be applied to the
combustible or limited-combustibleconstruction, not to the duct itself.
Exception: Field applied grease duct
enclosures and factory-built grease ductenclosures
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Field Applied Protection
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Duct Enclosures
Field applied grease duct enclosure: Alisted system evaluated for reduced
clearances and as an alternative to aduct with its fire-rated enclosure.
Factory-built grease duct enclosure: Alisted factorybuilt grease ductenclosure system evaluated forreduced clearances to combustiblesand as an alternative to a duct with its
fire-rated enclosure.
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EXHAUST HOODS
Type 1: Hoods designed for greaseexhaust applications
Type 2: Hoods designed for heatand steam removal and othernongrease applications. (NFPA 96does not cover)
NFPA 96: 2-1, 1998 Edition
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Exhaust Hoods
Hoods shall be constructed of 18 gagesteel or 20 gage stainless.
All seams, joints, and penetrations ofthe hood enclosure that direct andcapture grease-laden vapors and
exhaust gases shall have a liquidtightcontinuous weld external weld.
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Hood Integrity
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Exhaust Hood
Hoods must be sized and configured toprovide for the capture and removal of
grease-laden vapors. Size:
Configuration:
Backshelf/Proximity Hoods
Short-Circuit Hoods Face Discharge Makeup Hoods
Exhaust Only Hoods w/Supply Plenums
NFPA 96: 2-2, 1998 Edition
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Short Circuit Hoods
Hood performance is principallydependent upon net exhaust.
Net exhaust = Total exhaustinternal makeup
Large airflows are required highfirst cost & operating cost.
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Backshelf Hood
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Face Discharge Makeup
Hood Originally designed
for non-air-
conditionedkitchens
Makeup airbecomes load to
kitchen HVAC
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Exhaust Only Hood Cross
Section
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Exhaust OnlyHood w/Supply
Plenum
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Hood w/Supply Plenums
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Fire Dampers at Hoods
Fire dampers are installed in supply airconnections where they penetrate the
hood. Fire dampers are not installed in
exhaust ducts.
Fire dampers are not required insupply plenums that are isolated fromthe continuously welded shell.
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Filters and Baffles
They are required!
They must be 18 inches from cooking
surface. (Hoods above char-broilers must be4 ft above the cooking surface).
Filters must be installed at an angle of notless than 45 degrees
Filters must be easily accessible andremovable for cleaning.
NFPA 96: Ch.3, 1998 Edition
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EXHAUST DUCTS
Ducts can not pass through fire wallsor fire partitions.
Ducts cannot have dips or traps.
Clearances must be maintained.
Ducts must be 16 gage steel or 18
gage stainless.
Seams and joints shall have liquidtight external welds.
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Openings in Exhaust Ducts
Location At changes of direction For damper cleaning and inspection At both sides of inline fans
Construction On horizontal ducts20x20; if size is not possible, provide
openings large enough for cleaning every 12 feet. Access openings shall be of the same material and thickness
as the duct. Access panels shall have a gasket or sealant that is rated for
15000
F and shall be grease tight. Enclosure openings are required to reach access panels.They shall be protected by approved self-closing firedoors.
NFPA 96: 4-3, 1998 Edition
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Exhaust Ducts Exterior
Fasteners cannot penetrate duct walls.
Ducts must be painted or be
constructed of stainless steel.
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Exhaust Ducts Interior
Enclosures must be provided forbuildings more than one story, and
when penetrating a rated floor /ceilingassembly.
Enclosure shall be sealed around the
duct at the bottom.Exception: Field applied or factory
applied grease duct enclosures.NFPA 96: 4-7, 1998 Edition
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Clearances at Enclosures
18 to combustible construction 6 to noncombustible or limited-combustible
construction Clearances may be reduced with field
applied or factory applied grease ductenclosures.
Multiple ducts are not permitted in a single
enclosure
(SMC only requires 6 clearance)
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Rooftop Terminations
Maintain 10 feet clearance to adjacentbuildings, property lines, and air
intakes, or locate exhaust 3 feet aboveair intakes.
Ductwork must extend 18 above
roof.
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Fans
Fans must be listed for commercialcooking equipment.
Rooftop Fans Rooftop fans must be hinged.
Exhaust outlet must be 40 inches above
roof. Termination must have a grease trap.
Safe access must be provided to the fan
for inspection and cleaning
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Fans
Wall Termination Fans
Wall must be noncombustible
Maintain a minimum of 10 feet clearance fromoutlet to adjacent buildings, property lines,grade level, combustible construction, electricalequipment, air intakes or operable windows.
Air intakes or operable windows above exhaustshall be 10 feet plus 0.25 feet for each 1 degreefrom horizontal.
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Airflow
Air flow has traditionally been 1500 ft/minminimum. This is changing with the newer
codes. Air volumes should be of sufficient level to
capture and remove grease-laden cookingvapors.
Makeup air shall prevent negative pressuresfrom exceeding 0.02 wc in the cookingarea.
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Fire Suppression Systems
Automatic fireextinguishing
systems must be inaccordance with
NFPA 12 - CO2 NFPA 13 Wet
NFPA 17 DryChemical
NFPA 17A WetChemical
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Ansul System
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Pyrochem System
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Fire Suppression Systems
Exhaust fans must continue to operate after theextinguishing system has been activated. Fans donot have to be started upon activation of the
extinguishing system. Makeup air supplied internally to the hood must be
shut off when fire suppression system activates.
All sources of fuel and electric power that produceheat to all equipment requiring protection by that
system shall automatically shut off upon activationof any extinguishing system.
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Fire Suppression Systems
A means of manual activation must be provided inthe path of egress. (SMC requires it to be from 10-20 feet of hood.)
An audible alarm or visible indicator shall beprovided.
If fire alarm system is installed in building, it shallbe activated.
If electric power is required to operate the firesuppression system, it shall have a backup powersupply or all sources of fuel shall automatically shutoff when the system is inoperable.
Portable fire extinguishers
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Fire Suppression System
Inspection and Servicing Systems are required to be inspected every 6
months by properly trained and qualified
persons.All devices, actuators, detectors, andcomponents shall be checked for properoperation.
Fusible links and automatic sprinkler heads shall
be replaced at least annually, or morefrequently. If required, certificates of inspection and
maintenance shall be forwarded to the AHJ.
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Cleaning and Inspection
The entire system shall be inspected byproperly trained and certified personnel. Quarterly high volume operations (24 hour,
charbroiling) Semi-annually moderate volume
Annually low-volume (churches)
During inspection if the system is found to
be contaminated with grease, the entiresystem shall be cleaned by properly trainedand certified personnel.
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Cleaning and Inspection
Hoods, ducts, fans, etc. shall becleaned as needed to prevent them
from becoming heavily contaminatedwith grease.
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Code Updates
NFPA 96
International Mechanical Code
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Revisions to NFPA 96
Minimum Air Velocity through a greaseduct
1,500 ft/min (1998 edition) 1,200 ft/min (2001 edition)
500 ft/min (Errata 96-01-01 to 2001
edition in January 2002
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NFPA 96 2001
Protection shall be provided on thewall down to the floor or to
noncombustible material. Horizontal duct support systems shall
be designed for weight of duct plus800 lbs. at any point.
Penetrations to ducts and hoods shallbe listed.
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NFPA 96 2001
A minimum of 5 feet horizontalclearance from fan to combustible
material.
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NFPA 2004 under review
Chapter 15, Down Draft ApplianceVentilation Systems
A new section requiring a 20 x 20 openingfor personal entry for duct cleaning
A requirement for factory-built ductenclosures and duct-wrapped grease duct
systems to be listed in accordance with UL2221, Tests of Fire Resistive Duct Enclosure
Assemblies.
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International MechanicalCode
2000 Code
Performance Test
Net Exhaust 2003 Code
Capture and Containment Test
Net Exhaust
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Capture and ContainmentTest
Adjust and verify all exhaust and makeupairflows.
Operate equipment at cooking conditions
Verify capture and containment with smokepuffers
Verify pressurization, and adjust if
necessary Building positive to outdoors, kitchen negative todining
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Capture and ContainmentTest