NFPA 96 and Building Code Requirements for Commercial Kitchen Hood Systems

1
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

2
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 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.

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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 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.

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9 inch clearance reduction
7
3 inch clearance reduction
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Clearances
9
Clearances
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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

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Field Applied Protection
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Duct Enclosures

• 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
  factorybuilt grease duct enclosure system
  evaluated for reduced clearances to combustibles
  and as an alternative to a duct with its
  fire-rated enclosure.

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EXHAUST HOODS

• 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
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Exhaust Hoods

• 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.

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Hood Integrity
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Exhaust Hood

• Hoods must be sized and configured to provide 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 principally dependent upon
  net exhaust.
• Net exhaust Total exhaust internal makeup
• Large airflows are required high first cost
  operating cost.

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Backshelf Hood
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Face Discharge Makeup Hood

• Originally designed for non-air-conditioned
  kitchens
• Makeup air becomes load to kitchen HVAC

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Exhaust Only Hood Cross Section
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Exhaust Only Hood 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 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.

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Filters and Baffles

• 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
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EXHAUST DUCTS

• 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.

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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 ducts 20x20 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
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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 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
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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 duct enclosures.
• 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 adjacent buildings
  property lines and air intakes or locate
  exhaust 3 feet above air intakes.
• Ductwork must extend 18 above roof.

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Fans

• 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

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Fans

• 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.

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Airflow

• 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.

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Fire Suppression Systems

• Automatic fire extinguishing systems must be in
  accordance with
• NFPA 12 - CO2
• NFPA 13 Wet
• NFPA 17 Dry Chemical
• NFPA 17A Wet Chemical

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Ansul System
36
Pyrochem System
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Fire Suppression Systems

• 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.

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Fire Suppression Systems

• A means of manual activation must be provided in
  the path of egress. (SMC requires it to be from
  10-20 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

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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 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.

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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.

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Cleaning and Inspection

• Hoods ducts fans etc. shall be cleaned as
  needed to prevent them from becoming heavily
  contaminated with 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 grease duct
• 1500 ft/min (1998 edition)
• 1200 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 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.

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NFPA 96 2001

• A minimum of 5 feet horizontal clearance from fan
  to combustible material.

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NFPA 2004 under review

• 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.

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International Mechanical Code

• 2000 Code
• Performance Test
• Net Exhaust
• 2003 Code
• Capture and Containment Test
• Net Exhaust

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Capture and Containment Test

• 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

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Capture and Containment Test