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 • Problem Areas • General Requirements • Hoods • Exhaust Ducts • Fans • Fire Suppression System • Code Changes • NFPA 96 • International Mechanical Code (IMC)
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.
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.
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
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 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 • 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 • 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.
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
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.
Face Discharge Makeup Hood • Originally designed for non-air-conditioned kitchens • Makeup air becomes load to kitchen HVAC
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.
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
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.
Openings in Exhaust Ducts • Location • At changes of direction • For damper cleaning and inspection • At both sides of inline fans • Construction • 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 • 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 • 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 • 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 • 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 • 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 • 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 • Automatic fire extinguishing systems must be in accordance with • NFPA 12 - CO2 • NFPA 13 – Wet • NFPA 17 – Dry Chemical • NFPA 17A – Wet Chemical
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.
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
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.
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 • Hoods, ducts, fans, etc. shall be cleaned as needed to prevent them from becoming heavily contaminated with grease.
Code Updates • 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 • 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 • A minimum of 5 feet horizontal clearance from fan to combustible material.
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.”
International Mechanical Code • 2000 Code • Performance Test • Net Exhaust • 2003 Code • Capture and Containment Test • Net Exhaust
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