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 Code Changes General Requirements Hoods
Exhaust Ducts
Fans
Fire Suppression System
Code Changes
NFPA 96
International Mechanical Code (IMC)

3. 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.

4. Clearances 18 inches to combustible material
3 inches to limited-combustible material
0 inches to noncombustible material

5. 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.

6. 9 inch clearance reduction

7. 3 inch clearance reduction

8. Clearances

9. Clearances

10. 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

11. Field Applied Protection

12. 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.

13. 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

14. 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.

15. Hood Integrity

16. 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

17. 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.

18. Backshelf Hood

19. Face Discharge Makeup Hood
Originally designed for non-air-conditioned kitchens
Makeup air becomes load to kitchen HVAC

20. Exhaust Only Hood Cross Section

21. Exhaust Only Hood w/Supply Plenum

22. Hood w/Supply Plenums

23. 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.

24. 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

25. 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.

26. 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

27. Exhaust Ducts – Exterior
Fasteners cannot penetrate duct walls.
Ducts must be painted or be constructed of stainless steel.

28. 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

29. 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)

30. 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.

31. 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

32. 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.

33. 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.

34. 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

35. Ansul System

36. Pyrochem System

37. 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.

38. Fire Suppression Systems
A means of manual activation must be provided in the path of egress. (SMC requires it to be from 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

39. 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.

40. 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.

41. Cleaning and Inspection
Hoods, ducts, fans, etc. shall be cleaned as needed to prevent them from becoming heavily contaminated with grease.

42. Code Updates
NFPA 96
International Mechanical Code

43. 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 to 2001 edition in January 2002
-1,500 ft/min has been in the codes since the 1930s (may have come from velocity of air in coal-burning furnaces)
-Number was reduced because of ASHRAE Research Project 1033-RP
Advantages of lower fan speeds:
-lower grease accumulation, less duct cleaning
-easier to retrofit
-reduced noise
-energy savings (less makeup air)

44. 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.

45. NFPA 96 – 2001
A minimum of 5 feet horizontal clearance from fan to combustible material.

46. 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.”

47. International Mechanical Code
Performance Test
Net Exhaust
2003 Code
Capture and Containment Test

48. 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

49. Capture and Containment Test