by

Jay A. Guy

The views and opinions expressed in this article do not necessarily reflect those of NAFED.

The current state-of-the-art fire suppression system mostrecognized by the fire protection industry is known as the wet chemical pre-engineered fire suppression system.   Wet chemicalsystems are designed, tested, and approved (or listed) toprovide fire protection for commercial kitchen hoods, ducts andappliances.  They provide efficient, automatic detector responsewith fast-acting fire suppression with no danger of re-flash or re-ignition.Recently, the industry has witnessed the use of water sprinklersystem protection, on a limited basis, in place ofpre-engineered wet chemical systems.  Water sprinkler systemsare usually used where a water supply is readily available orwhere a water sprinkler system exists in the building that canbe extended to provide restaurant protection. In order to qualify as substitutes for wet chemical pre-engineered systems, water sprinkler components and systems must be listed by Underwriters Laboratories, Inc. (UL); is  recognized by National Fire Protection Association (NFPA) Standards; be a constant source of agent for extinguishment; reduce clean up time; and, lower installation service cost.Water sprinkler systems do not always compare favorably withwet chemical systems, and there are some important reasons wet chemical systems are most often preferred by the industry's authorities having jurisdiction and end users. Comparisons of Water Sprinkler and Wet Chemical systems areas follows:

UL Listed by is a not-for-profit, independent organization that tests devices, systems, and materials for public safety. Manufacturers of products submitted for UL testing enter into anagreement with UL for the use of their listing mark andmaintenance of quality that complies with UL's requirements. However, UL states that listed products are not necessarilyequivalent in quality or merit.Water sprinklers, as components only, and wet chemical systems,are UL-listed.  However, there are some distinct differences regarding the thoroughness and scope of each listing.  Watersprinkler listings are found under Nozzles Spray Type Fixed (BGYZ)" in the UL 1990 Fire Equipment Protection Directory. The standard used to investigate products is UL 199 "Automatic Sprinklers For Fire Protection Service." The UL 199 standard does not address specific restaurant hood, duct, or appliance testing but only requires generic functional, strength, corrosion, and nozzle coverage criteria for automatic sprinklers.

On the other hand, wet chemical pre-engineered systems are UL-listed as complete systems intended for commercial restaurant hazards and are found under "Wet Chemical Solution Extinguishing System Units (GOAS)" in the UL 1990 Fire Equipment Protection Directory. Wet chemical systems are performance tested under the guidelines of UL text standard subject 300 "Fire Testing for Extinguishing System Units in Restaurant Cooking Appliances," which contains requirements for full-scale fire and flow testing. These requirements include strict performance of the system to extinguish fire on duct, hood, and all types of cooking appliances including deep fat fryers, griddles; gas, electric, char and chain broilers and other types of appliances. Worst-case fire tests of duct, hood, and appliances are conducted. The system must successfully extinguish the fire in all areas without splashing or re-igniting cooking grease. All wet chemical, pre-engineered system parts are listed and labeled by UL, certifying compliance with national standards of product safety performance and reliability.

When comparing test requirements for wet chemical systems to that of water sprinklers systems, it is often recognized by authorities having jurisdiction that water sprinkler performance testing does not consider all the variables, lacks coverage definition, and is not tested to worst case situations.

Recognized by NFPA

NFPA is an independent, voluntary membership, non-profit organization dedicated to safeguarding people and their environment from destructive fire. The association's basic activity involves development of fire code standards to minimize the possibility and effects of fire. Published standards are available for voluntary adoption by all levels of government, local to national, and other authorities having jurisdiction.

NFPA does not accept any liability resulting from compliance or noncompliance with the provisions given, for any restrictions imposed on materials or processes, or for the completeness of the text. NFPA has no power to enforce compliance of NFPA Fire Codes. Both water sprinkler and wet chemical systems are recognized by several NFPA Fire Codes. The use of water sprinkler systems for restaurant hood, duct, and appliance protection is limited in scope, basically adopts standard water sprinkler calculations and standard automatic sprinkler system practices to the unique hazard of restaurant ducts, hoods and appliances. Wet chemical systems, however, are designed and tested for restaurant duct, hoods and appliances only, and are not used for any other hazard application.

Automatic water sprinkler systems are recognized by NFPA 96, "Installation of Equipment for the Removal of Smoke and Grease Laden Vapors From Commercial Cooking Equipment" - 1987 Edition. Chapter 7 recognizes sprinkler systems when installed in compliance with NFPA 13, with the following exceptions:

• A sprinkler system does not require manual actuation. The lack of manual actuation removes the flexibility and potential backup often necessary to activate the system and extinguish the fire before it becomes catastrophic. If manual actuation were used to discharge the water system, the potential for excess flooding and water damage exists (wet chemical systems require manual actuation in accordance with NFPA 17A and no flooding or overflow will occur.)
• Simultaneous automatic operation of all sprinkler heads in a single hazard area is not required. If all sprinkler heads are not actuated simultaneously and a single sprinkler head does not extinguish the fire, potential exists for a fire to increase substantially before additional sprinklers operate. (Wet chemical systems require simultaneous actuation and discharge of all nozzles in all hazard areas.)

NFPA 15 - "Water Spray Fixed Systems for Fire Protection" -1985 Edition, includes no specific applications requirements for commercial restaurant cooking hazards. (Wet chemical systems are recognized in the NFPA 17A standard for fire extinguishment in order to eliminate fire danger, damage and downtime. According to chapter 4-6.2, adequate provisions shall be made for sprinkler system drainage. (Wet chemical systems do not require drainage as danger of agent flooding is not present.)

NFPA 13 - "Installation of Sprinkler Systems" - 1989 Edition, Chapter 4-4.17, recognized additional sprinklers or automatic spray nozzles to protect commercial type restaurant cooking equipment.

• Standard sprinklers shall be located to provide protection. (Wet chemical systems apply nozzles designed for restaurant duct, hood, and appliances.)
• Exhaust ducts require nozzles at duct entrance and at the top and midpoint of each vertical riser.
• Horizontal ducts require nozzles at duct entrance and at 10 ft. centers. (Wet chemical systems only require nozzle at duct entrance with fan on or off.) *Each hood duct collar shall have one automatic spray nozzle. (No nozzle required by wet chemical system.) *Sprinklers subject to freezing shall be properly protected. (Wet chemical systems nozzles do not require freezing protection.)
• An approved line strainer shall be installed in the main water supply. (Wet chemical systems do not require line strainers.)
• Sprinklers and automatic spray nozzles shall be replaced annually except if no buildup of grease or other material is present. (Wet chemical nozzles do not require annual replacement as they are protected with blow off caps and pipes using teflon tape to prevent grease entry and buildup.)
• Bafflers are required midway between sprinklers when sprinkler are less than 6 feet apart to prevent wetting of adjacent sprinklers, thus delaying their operation. (Baffles are not required between wet chemical nozzles as all nozzles discharge simultaneously to provide complete coverage over all hazard areas.)

Wet Chemical Pre-Engineered Systems are recognized by:

• NFPA 96 - "Installation of Equipment for Removal of Smoke and Grease Laden Vapors from Commercial Cooking Equipment" 1987 Edition, in which Chapter 7 recognizes wet chemical pre-engineered systems when installed in compliance with NFPA 17A.
• NFPA 17A - "Wet Chemical Extinguishing Systems" 1990 Edition, recognizes wet chemical pre-engineered systems as having predetermined flow rates, nozzle pressures, quantities of liquid agent and types of nozzles and all system components specifically applied to commercial restaurant duct, hood and appliances prescribed by a testing laboratory. Wet chemical listed components consist of agent tank, nozzles, releasing device, fuse link detection, manual pull station, and gas/electric shutoff devices.

Constant Supply of Agent for Extinguishment

An important difference between water sprinkler systems and wet chemical systems is the quality and quantity of agent applied to restaurant hazards.

Water sprinkler systems have an unlimited source and often a large quantity of water is used to ensure extinguishment, and securement of restaurant hazards are ladened with cooking grease.

Water agent extinguishes restaurant hazards by smothering, producing steam and surface cooling below auto ignition temperature. Nozzle discharge tests have demonstrated that initial application of water onto deep fat fryers may result in a violent reaction resulting in a fireball effect. Constant application of water eventually stabilizes the grease fire and extinguishment takes place. The violent fireball action creates danger to restaurant employees and could spread the fire to other hazard areas.

Constant agent supply sometimes results in the application of too much water. Upon actuation of sprinkler heads, water will discharge until the fire department or a knowledgeable person shuts off the system's main shut off valve. In a panic situation, an excess amount of water could be discharged unnecessarily.

Constant agent supply could result in an overflow situation causing water and cooking grease to spill over, whereby the required drainage facilities may not handle the overflow and the adjacent area could become slippery, creating a danger to employees or firemen.

Wet chemical pre-engineered systems are designed to discharge a predetermined quantity of agent in accordance with UL test criteria and listing. A typical wet chemical system discharges three to four gallons of agent in about 30 seconds. This quantity has been proven effective because of the characteristic of wet chemical, its composition and the way it reacts to fires involving grease-laden restaurant hazards. Wet chemical agent extinguishes by cooling the grease surface of the grease. This acts a insulation between hot grease and the atmosphere, helping to prevent escape of combustible vapors.

When applying wet chemical agent, there is no need for a constant supply. There is no need to manually shut off the system and no danger of violent agent reaction that may spread flame or spill cooking oil that could injure personnel.

Reduced Cleanup Time

Cleanup costs and downtime as a result of a fire protection discharge can be very costly to the restaurant owner. Cleanup time and expense is often directly proportional to the quantity and length of time the agent is discharged.

The quantity of water that flows from sprinkler systems is unpredictable. It depends on the number of sprinkler heads that actuate, the size and length of distribution pipe used, nozzle pressure and most importantly, how long the water system is allowed to discharge before the shut-off valve is manually closed. The water discharge could cause an overflow situation, damage to electrical control equipment, a hazard to employees and firemen, and a prolonged downtime.

Wet chemical systems discharge a limited quantity of agent, will not cause overflow, require less downtime, and are less costly to recharge. Surfaces coated with wet chemical agent must be cleaned as soon as possible with soap and water to avoid staining of appliances, keeping cleanup to a minimum.

Lower Cost Installation

The installation of a water sprinkler system for restaurant cooking appliances is not always as simple as adding on to the existing sprinkler system that protects the remaining portion of the building. The piping configuration can be more complicated than wet chemical systems, especially in the duct area. Standard sprinklers or automatic spray nozzles are required at duct entrances, the tip of each vertical rise, and at midpoint of each duct offset. Horizontal ducts require sprinklers every ten feet of duct. Listed below are wet chemical pre-engineered systems that only require nozzles located at the duct entrance and they are listed for unlimited ducts.

Sprinklers or automatic spray nozzles in the exhaust duct subject to freezing must be protected against freezing by insulating coverings, frost proof casings, etc. Wet chemical systems are dry pipe systems and do not require freeze protection of any kind.

Access doors or panels must be provided for all sprinklers or automatic spray nozzles for examination or replacement. Wet chemical pre-engineered system nozzles do not require access doors or panels since all nozzles are accessible for servicing.

Such additional components as an indicating valve, line strainers and a system test connection are also required as part of sprinkler or automatic spray nozzle installations. Also, 6" x 8" metal baffles are required between sprinklers that are installed within six feet of each other to avoid delay of the adjacent sprinkler operation.

Wet chemical pre-engineered systems require no special distribution components but include a hardware package consisting of an agent tank, agent, fusible link detection system, releasing device, manual actuator and gas and/or electric shutdown devices.

Conclusion

The discussion in this text compares differences in the application of both water sprinkler and wet chemical systems to commercial restaurant duct, hood and appliance fire hazards. The most important factor is that wet chemical pre-engineered systems provide complete protection to all hazards simultaneously and are UL-tested and listed specifically for restaurant hazard applications. Agent characteristics, simultaneous coverage and specific test criteria make wet chemical pre-engineered systems the state of the art fire protection system for restaurant applications.