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
Course Outline
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Problem Areas
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General Requirements
Hoods
Exhaust Ducts
Fans
Fire Suppression System
Code Changes
– NFPA 96
– International Mechanical Code (IMC)
GENERAL REQUIREMENTS
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Where are commercial hoods required?
– NFPA 96: “Cooking equipment used in processes
producing smoke and grease-laden vapors shall
be equipped with…
– NFPA 96 – A-1-1 “…intended to include
residential cooking equipment where used for
purposes other than residential family use…”
– SMC gives exceptions for domestic equipment
installed in dwelling units and ovens do not heat
food above 2120F.
Clearances
– 18 inches to combustible material
– 3 inches to limited-combustible material
– 0 inches to noncombustible material
Exceptions
When the hood is listed for lesser clearances
 If the combustible material is protected as
follows:

– 28 gage sheet metal spaced out 1 inch on
noncombustible spacers – 9 inch clearance to
combustible material
– 22 gage sheet metal on 1 inch mineral wool bats or
ceramic 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 to
zero clearance where protected by noncombustible
materials or materials listed for the purpose of reducing
clearance, and acceptable to the AHJ.
9 inch clearance reduction
3 inch clearance reduction
Clearances
Clearances
Duct Clearances

Protection methods for ducts to reduce
clearances shall be applied to the
combustible or limited-combustible
construction, not to the duct itself.
– Exception: Field applied grease duct
enclosures and factory-built grease duct
enclosures
Field Applied Protection
Duct Enclosures
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Field applied grease duct enclosure: A
listed system evaluated for reduced
clearances and as an alternative to a
duct with its fire-rated enclosure.
Factory-built grease duct enclosure: A
listed factory–built grease duct
enclosure system evaluated for
reduced clearances to combustibles
and as an alternative to a duct with its
fire-rated enclosure.
EXHAUST HOODS
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Type 1: Hoods designed for grease
exhaust applications
Type 2: Hoods designed for heat
and steam removal and other
nongrease applications. (NFPA 96
does not cover)
NFPA 96: 2-1, 1998 Edition
Exhaust Hoods
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Hoods shall be constructed of 18 gage
steel or 20 gage stainless.
All seams, joints, and penetrations of
the hood enclosure that direct and
capture grease-laden vapors and
exhaust gases shall have a liquidtight
continuous weld external weld.
Hood Integrity
Exhaust Hood

Hoods must be sized and configured to
provide for the capture and removal of
grease-laden vapors.
NFPA 96: 2-2, 1998 Edition
– Size:
– Configuration:
 Backshelf/Proximity Hoods
 Short-Circuit Hoods
 Face Discharge Makeup Hoods
 Exhaust Only Hoods w/Supply Plenums
Short Circuit Hoods
Hood performance is principally
dependent upon net exhaust.
 Net exhaust = Total exhaust –
internal makeup
 Large airflows are required – high
first cost & operating cost.

Backshelf Hood
Face Discharge Makeup
Hood
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Originally designed
for non-airconditioned
kitchens
Makeup air
becomes load to
kitchen HVAC
Exhaust Only Hood Cross
Section
Exhaust Only
Hood w/Supply
Plenum
Hood w/Supply Plenums
Fire Dampers at Hoods
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Fire dampers are installed in supply air
connections where they penetrate the
hood.
Fire dampers are not installed in
exhaust ducts.
Fire dampers are not required in
supply plenums that are isolated from
the continuously welded shell.
Filters and Baffles
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They are required!
They must be 18 inches from cooking
surface. (Hoods above char-broilers must be
4 ft above the cooking surface).
Filters must be installed at an angle of not
less than 45 degrees
Filters must be easily accessible and
removable for cleaning.
NFPA 96: Ch.3, 1998 Edition
EXHAUST DUCTS
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Ducts can not pass through fire walls
or 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 liquid tight
external welds.
Openings in Exhaust Ducts
– Location
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At changes of direction
For damper cleaning and inspection
At both sides of inline fans
– Construction
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On horizontal ducts – 20”x20”; 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
15000F and shall be grease tight.
– Enclosure openings are required to reach access panels.
They shall be protected by approved self-closing fire
doors.
NFPA 96: 4-3, 1998 Edition
Exhaust Ducts – Exterior
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Fasteners cannot penetrate duct walls.
Ducts must be painted or be
constructed of stainless steel.
Exhaust Ducts – Interior
Enclosures must be provided for
buildings more than one story, and
when penetrating a rated floor /ceiling
assembly.
 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
Clearances at Enclosures
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18” to combustible construction
6” to noncombustible or limited-combustible
construction
Clearances may be reduced with field
applied or factory applied grease duct
enclosures.
Multiple ducts are not permitted in a single
enclosure
(SMC only requires 6” clearance)
Rooftop Terminations
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Maintain 10 feet clearance to adjacent
buildings, property lines, and air
intakes, or locate exhaust 3 feet above
air intakes.
Ductwork must extend 18 “ above
roof.
Fans
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Fans must be listed for commercial
cooking 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
Fans
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Wall Termination Fans
– Wall must be noncombustible
– Maintain a minimum of 10 feet clearance from
outlet to adjacent buildings, property lines,
grade level, combustible construction, electrical
equipment, air intakes or operable windows.
– Air intakes or operable windows above exhaust
shall be 10 feet plus 0.25 feet for each 1 degree
from horizontal.
Airflow
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Air flow has traditionally been 1500 ft/min
minimum. This is changing with the newer
codes.
Air volumes should be of sufficient level to
capture and remove grease-laden cooking
vapors.
Makeup air shall prevent negative pressures
from exceeding 0.02” wc in the cooking
area.
Fire Suppression Systems
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Automatic fire
extinguishing
systems must be in
accordance with
– NFPA 12 - CO2
– NFPA 13 – Wet
– NFPA 17 – Dry
Chemical
– NFPA 17A – Wet
Chemical
Ansul System
Pyrochem System
Fire Suppression Systems
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Exhaust fans must continue to operate after the
extinguishing system has been activated. Fans do
not 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 produce
heat to all equipment requiring protection by that
system shall automatically shut off upon activation
of any extinguishing system.
Fire Suppression Systems
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A means of manual activation must be provided in
the path of egress. (SMC requires it to be from 1020 feet of hood.)
An audible alarm or visible indicator shall be
provided.
If fire alarm system is installed in building, it shall
be activated.
If electric power is required to operate the fire
suppression system, it shall have a backup power
supply or all sources of fuel shall automatically shut
off when the system is inoperable.
Portable fire extinguishers
Fire Suppression System
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Inspection and Servicing
– Systems are required to be inspected every 6
months by properly trained and qualified
persons.
– All devices, actuators, detectors, and
components shall be checked for proper
operation.
– Fusible links and automatic sprinkler heads shall
be replaced at least annually, or more frequently.
– If required, certificates of inspection and
maintenance shall be forwarded to the AHJ.
Cleaning and Inspection

The entire system shall be inspected by
properly 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 entire
system shall be cleaned by properly trained
and certified personnel.
Cleaning and Inspection
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Hoods, ducts, fans, etc. shall be
cleaned as needed to prevent them
from becoming heavily contaminated
with grease.
Code Updates
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
NFPA 96
International Mechanical Code
Revisions to NFPA 96

Minimum Air Velocity through a grease
duct
– 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
NFPA 96 – 2001
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Protection shall be provided on the
wall down to the floor or to
noncombustible material.
Horizontal duct support systems shall
be designed for weight of duct plus
800 lbs. at any point.
Penetrations to ducts and hoods shall
be listed.
NFPA 96 – 2001
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A minimum of 5 feet horizontal
clearance from fan to combustible
material.
NFPA 2004 under review

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Chapter 15, Down Draft Appliance
Ventilation Systems
A new section requiring a 20” x 20” opening
for personal entry for duct cleaning
A requirement for factory-built duct
enclosures and duct-wrapped grease duct
systems to be listed in accordance with UL
2221, “Tests of Fire Resistive Duct Enclosure
Assemblies.”
International Mechanical
Code

2000 Code
– Performance Test
– Net Exhaust

2003 Code
– Capture and Containment Test
– Net Exhaust
Capture and Containment
Test
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Adjust and verify all exhaust and makeup
airflows.
Operate equipment at cooking conditions
Verify capture and containment with smoke
puffers
Verify pressurization, and adjust if necessary
– Building positive to outdoors, kitchen negative to
dining
Capture and Containment
Test