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FIR 3301, Fire Behavior and Combustion 1 Course Learning Outcomes for Unit VII Upon completion of this unit, students should be able to: 7. Demonstrate knowledge of the characteristics of water as a fire suppression agent. 7.1. Illustrate different ways water suppresses fire. 7.2. Describe the roles of suppression-enhancing additives to water. 8. Articulate other suppression agents and strategies. 8.1. Analyze the types of nonaqueous fire suppressants. 8.2. Evaluate the use of halon fire extinguishers in today’s environment. 9. Compare other methods and techniques of fire extinguishments. 9.1. Describe the different types of suppression agents that are effective on fire. Reading Assignment Chapter 13: Fire Fighting Chemicals Unit Lesson According to Gann and Friedman (2015), combustible materials have numerous differences, including different products requiring different suppression systems to address these differences as a factor in the design. The authors continue by suggesting that in order to understand suppression you first must understand the following type of extinguishment: flame or fire extinguishment, fire control, flame or fire suppression, fire inerting, and flammability. Why is it important to understand the differences among fire control and fire inerting? Gann and Friedman (2015) explain that each of these groups requires a different extinguishment tactic in order to prevent reignition. Why? Hasn’t water been used primarily for the extinguishment of fire? In fact, aren’t aqueous agents the oldest group of agents used in the extinguishment of fires? The first system using aqueous agents was installed in 1812 at the Theatre Royal in the United Kingdom (Rapid Fire Protection, 2014). The authors stated that this sprinkler system was similar in design to systems today with branches and water mains, but it was not automatic. “The first automatic sprinkler system was built in 1875” (Gann &Friedman, 2015, p. 226) and this system was installed in a piano factory in New Haven, Connecticut. That first system is conceptually comparable to the systems used today (Gann & Friedman, 2015; Rapid Fire Protection, 2014). Since 1812 water has been the primary aqueous agent used for extinguishing fires using sprinkler systems and there have been mainly three types of fire automatic sprinkler systems used: preaction system, dry pipe systems, and the wet fire sprinkler system (Gagnon, 2008). Each of these systems discharges small droplets or large droplets of water to suppress the fire. IFSTA (2008) stated, “There are two general types of sprinkler coverage: complete sprinkler coverage and partial sprinkler coverage” (p. 842). The authors continue to define complete sprinkler coverage as containing or controlling the fire in the entire structure and partial sprinkler coverage as protecting only areas of the structure that may have high hazards. Another aqueous agent used to control, suppress, or extinguish fires is the water mist system. According to Arvidson (2008), “The knowledge about the benefits of using finely atomized water sprays is not new either.” The author continues to explain that water mist systems have been commercially available since the 1930s using the atomizing nozzle. As with sprinkler systems, there are several different application methods using water mist systems; these methods may include local application method, total flooding method, or zoned applications (Gagnon, 2008). The local application method is a method of suppression that applies the agent directly to the hazard or foreseeable hazard. This differs from the total flooding method where the inclusion is UNIT VII STUDY GUIDE Characteristics of Water as a Fire Suppression Agent FIR 3301, Fire Behavior and Combustion 2 UNIT x STUDY GUIDE Title filled with the aqueous agent. In large structures that are not compartmented, a zoned system with individual detection systems and zones can activate autonomously, in conjunction with other zones (Gagnon, 2008). According to Gagnon (2008), there are four types of systems that are designed in accordance with NFPA 750: deluge water mist systems, wet pipe water mist systems, preaction water mist systems, and dry pipe water mist systems. Each of these systems uses “evaporating mist droplets [to] remove heat, either at the surface of the combustible or within the flame” (Gann & Friedman, 2015, p. 229). Other aqueous agents that Gann and Friedman (2015) referred to as enhanced water are foams. According to Chemguard (2005): Foam has been used as a fire-extinguishing medium for flammable and combustible liquids. Unlike other extinguishing agents - water, dry chemical, CO2, etc., a stable aqueous foam can extinguish a flammable or combustible liquid fire by the combined mechanisms of cooling, separating the flame/ignition source from the product surface, suppressing vapors and smothering. It can also secure for extended periods of time against reflash or reignition. (p. 1) George (2006) and Gagnon (2008) suggest extinguishment using foam is accomplished by smothering, cooling, insulating, and penetrating. According to Gann and Friedman (2015) the principle applications of aqueous foam is for flammability liquids fires (Class B fires) which are two dimensional and three dimensional solid fuel fires (Class A fires). Points to Ponder You are dispatched to assist a small neighboring fire district incident involving an overturned truck carrying three 55 gallon containers of a fuel that was on fire. As you approached the scene you note that firefighters were applying some type of foam from a hand-held package that was attached to the end of a booster line over the spilled fuel and fire. As they were lobbing foam from a short section of hose to blanket the spill, the foam was not holding and the fire appeared to burn back onto the foam. You identified the placard on one of the 55 gallon drum as 3475. As you looked in the emergency response guidebook you found the product to be ethanol fuel. At the same time the driver approached and stated he was carrying E85 (Ethanol Fuel). The officer from the neighboring fire district stated they were using AFFF and it was not making any headway as the foam continued to break up and appeared to be mixing with the product as the fire burned back towards them. Why wasn’t the method of blanketing the product and fire effective using AFFF (Aqueous film-forming foam)? Were their setting and application rates wrong? Gann and Friedman (2015) suggest gasoline mixtures containing ethanol should be treated differently than non-ethanol fuels because these mixtures are miscible in water. The authors warn, “Even a small amount of these substances mixed with hydrocarbons (e.g., in gasohol) causes the rapid breakdown of ordinary firefighting foams” (p. 232). Gagnon (2008) states there are three types of foam: low-, medium-, and high-expansion. High-expansion foams are primarily used on three-dimensional fires where the medium and low expansion foams are predominantly used on two-dimensional fires. Low expansion foam systems are designed in accordance with NFPA 11 (2005 Edition), to protect fires primarily associated with flammable and combustible liquids (Gagnon, 2008). Available foams include protein based, fluoroprotein based, aqueous film forming foam, alcohol resistant concentrates, and chemical foams (Gagnon, 2008). High-expansion foam is comprised of bubble shells that form an extensive layer of bubbles filled with air (Gagnon, 2008). “The very lightweight bubbles are easily blown away by wind, so these foams are not well suited for use on out-door fires” (Gann & Friedman, 2015 p. 233) A clean agent, such as an inert gas, is another means to extinguish combustible materials. The most commonly used inert gas is carbon dioxide (Gann & Friedman, 2015). The National Fire Protection Association (NFPA) Standard 12 recognizes four different types of carbon dioxide systems. According to Gagnon (2008), the four types of systems are: total flooding carbon dioxide, local application carbon dioxide, hand hose line carbon dioxide, and standpipe systems with mobile supply. Total flooding carbon dioxide systems are normally found where there is an enclosed room that presents the risk of surface fires or deep seated fires (Gagnon, 2008). Local application carbon dioxide systems are designed in areas where there is no enclosure “or where a total flooding system could endanger personnel” (Gagnon, 2008, p. 272). In most cases the area that is being protected is small, has limited space, and the cost benefit to utilize a total flooding system is not only impractical notnot cost beneficial. Hand hose line systems are very unique and, unlike total FIR 3301, Fire Behavior and Combustion 3 UNIT x STUDY GUIDE Title flooding or local application, this system is only operated manually “in the vicinity of a perceived hazard either as a supplement” (Gagnon, 2008, p. 272). Standpipe systems and mobile supply is typically used in an environment where personnel are specially trained to use and recognize the hazards associated with a carbon dioxide system. This type of system is usually found at chemical facilities that are equipped with a highly trained fire brigade of specialized firefighters (Gagnon, 2008). In this unit you will evaluate the chemicals that are used to extinguish or control fires. You will also distinguish among fire extinguishment, fire control, and fire inerting. You will categorize the types of fires on which they are effective, the chemical phase, the mechanism of action, the mode of application, and the application system. This unit covers the four classifications of fires, as used in the United States. You will also analyze the different ways in which water suppresses a fire, depending on its method of delivery. References Arvidson, M. (2008, September 17). The history of the development of modern water mist system technology in Sweden. Paper presented at the 8th International Water Mist Conference, Copenhagen Denmark. Chemguard (2005, September). General Foam Information. Mansfield, TX. [Data Sheet #D10D03010]. Gagnon, R. (2008). Design of special hazard and fire alarm systems (2nd ed.). Albany, NY: Delmar Learning. Gann, R., & Friedman, R. (2015). Principles of fire behavior and combustion (4th ed.). Quincy, MA: National Fire Protection Association. George, D. (2006). David’s fire equipment–foam basics. Retrieved from http://www.davidsfire.com/foam_basics.htm. IFSTA. (2008). Essentials of firefighting (5th ed.). Stillwater, OK: Fire Protection Publications, Oklahoma State University. Fire sprinkler history. (2014, May). Rapid Fire Protection. Retrieved from http://www.rapidfireinc.com/index.php?option=com_content&view=article&id=4&Itemid=5 Suggested Reading Fire Suppression Substitutes and Alternatives to Halon for U.S. Navy Applications ebrary Reader Author: National Research Council Staff Publisher: National Academies Press Date Published: 04/1997 http://site.ebrary.com/lib/columbiasu/docDetail.action?docID=10056957&p00=AFFF Foam Engineering : Fundamentals and Applications (2nd Edition) ebrary Reader Author: Stevenson, Paul Publisher: Wiley Date Published: 12/2011 http://site.ebrary.com/lib/columbiasu/docDetail.action?docID=10575582&p00=AFFF In order for the links above to function properly, you must first log into the myCSU Student Portal and access the database within the CSU Online Library. You may also access the resources by visiting the database and performing a search for the title or author. FIR 3301, Fire Behavior and Combustion 4 UNIT x STUDY GUIDE Title Learning Activities (Non-Graded) Review What You Have Learned The Challenging Questions at the end of Chapter 13, on page 252–253, will help you evaluate chemicals that are used to extinguish or control fires that are categorized by the types of fires on which they are effective, the chemical phase, the mechanism of action, the mode of application, and the application system. This is a non-graded activity, so you do not have to submit it. However, if you have difficulty or questions with the concepts involved, contact your instructor for additional discussion and/or explanation.