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FIR 2303, 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 fire suppression agents. 7.1 Illustrate different ways water suppresses fire. 7.2 Describe the roles of suppression-enhancing additives to water.
8. Compare the methods of fire extinguishments.
8.1 Describe the different types of suppression agents that are effective on fire.
Course/Unit Learning Outcomes
Learning Activity
7.1 Unit Lesson Chapter 13 Unit VII Final Project
7.2 Unit Lesson Chapter 13 Unit VII Final Project
8.1 Unit Lesson Chapter 13 Unit VII Final Project
Required Unit Resources Chapter 13: Fire Fighting Chemicals
Unit Lesson Recap In the previous unit, we covered fire effluents and smoke. We covered the different colors of smoke, with black and white being the most common. Smoke and soot is made up of aerosols and gases with soot being mainly carbon particles. The incandescent orange-yellow glow and black smoke emanating from the flame is from carbonaceous solid particles. Both soot and smoke reduce firefighters’ visibility in a fire, and the environment can change radically as the fire consumes more and more combustibles. Water as a Fire Suppression Agent Water is the oldest form of fire suppressant. Today, water is still the most common means of fire suppressant and slows the rate of combustion in three ways: cools the fuel and decreases the rate of pyrolysis; vaporizes into steam, lowering gas temperature and diluting oxygen feeding the flames; and absorbs enthalpy (Gann & Friedman, 2015). Some of the first fire brigades used water from buckets to extinguish fires. Today, buckets have been replaced with pre-connect hose lines and fire apparatus carrying hundreds of gallons of water. Today’s tactic is to apply water to the fire using pre-connects reducing flaming and limiting the fuel at the same time ventilation is being performed. Water is the most common suppression agent for water-based fire protection systems. Water-based sprinkler systems are used in residential and commercial structures today. These systems range from simple sprinkler systems and deluge-based systems to much more advanced misting systems. The first non-automatic water- based sprinkler system was installed in 1812, at the Theatre Royal, United Kingdom (Bellis, n.d.). The design
UNIT VII STUDY GUIDE
Characteristics of Water as a Fire Suppression Agent
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of the non-automatic system was similar to water-based systems today utilizing branches and water mains. In 1875, the first automatic sprinkler system was designed, and this system was installed in a piano factory in New Haven, Connecticut (Gann & Friedman, 2015). Important factors in defining the efficiency of water-based suppression systems from 1812 to present day are the droplet size, evaporation rate, and suspension time. Today, water can be enhanced to make the application more effective in water-based systems and pre- connect handlines. Some of the applications are wetting agents and foam. Fire Suppression Using Pre-Connect Handlines Fire attack pre-1980 for many fire departments was an exterior attack through the window or door from which the fire was showing. Then, post-1980 many fire instructors advocated the application of water from the unburned side and pushing the fire out through the burned side of the structure for victim survivability. It was thought that pushing the fire out the burned side would eliminate steam expansion, improving conditions in the house for any victims. Several studies have shown that applying water, regardless of where it is, will make conditions in the entire structure better (Kerber, 2012; Kerber, 2013; Lambert, 2014). These studies suggest that if fire is coming out of a window or door, applying water through the opening in a clockwise circular motion or “Z” pattern, for approximately 15 seconds, will make the environment more tenable for both firefighters and victims (Figure 1). After this, the firefighter should quickly access the fire in the fastest and safest way and apply water to the fire. This has been referred to as transitional attack, or softening the target (“Innovating Fire Attack,” 2013; Kerber, 2013; Lambert, 2014). With synthetic and other combustibles today, the reasoning behind the quick attack is reducing the speed at which the fire grows.
Water-Based Automatic Sprinkler Systems Sprinkler systems were designed to suppress or control fires and have not changed much over the years. The main reason automatic sprinkler systems were designed was for property conservation and protection. There are several types of sprinkler systems from wet pipe, dry pipe, pre-action, and deluge systems (Gagnon, 2008; Sturzenbecker et al., 2016). There are also special water-based systems, such as water mist and foam fire suppression systems. Sprinkler systems use two types of fusible links where heat from the fire melts the metal link or ruptures a glass bulb to activate the water-based system. The glass bulb has fluid in the bulb, and when heated, the vapor pressure of the fluid increases to the point where it exceeds the strength of the glass. Residential sprinklers actuate at air temperatures 135 °F to 170 °F (Gann & Friedman, 2015). Water- based systems discharge small droplets or large droplets of water to suppress the fire using complete sprinkler coverage and partial sprinkler coverage. Complete sprinkler coverage is designed for the entire structure, and partial coverage protects only the high hazard areas. Since 1930, water mist systems were designed as a water-based sprinkler system (Arvidson, 2008). Water mist systems use finely atomized water sprays as the application method to suppress fires. Water mist systems may include local application method, total flooding method, or zoned applications. Gagnon (2008) suggests the typical size of water mist drops are hundreds of micrometers in diameter and suppress fires by one of four methods: mist droplets remove heat; mist droplets generate steam; mist droplets block radiative heat transfer; and mist droplets cool the fuel surface.
Figure 1
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Enhanced Water What is enhanced water? How does enhanced water improve firefighting efforts? Concentrates are added to water to enhance their properties to improve application and significantly use less water, and they include thickeners, wetting agents, foam formers, film formers, and emulsifiers used to enhance water for suppression efforts. Some of the additives alter droplet size, improve water’s ability to spread over a surface, improve water’s ability to penetrate porous materials, and increase efficiency for heat absorption (Gann & Friedman, 2015). These additives are surfactants increasing its penetration and spreading ability. The additive can be as simple as inorganic salts that lower the freezing point to friction-reducing additives that increase the slipperiness of water. Other wetting additives are used to break down the high surface tension of water so it will penetrate many materials, such as upholstery. Wetting agents improve the efficiency of water in extinguishing Class A fuel fires (Gann & Friedman, 2015). The use on Class B fires requires much higher concentration rates than those requiring foam agents and is limited to non-water flammable liquids. Aqueous Foams What are the differences between wetting agents and foam? Foam concentrate is added to water and aerated to produce a foamy froth to extinguish flammable and combustible liquids by blanketing the product and fire. The primary use of Class B foams is to separate the fuel from air on large flammable liquid fires (Figure 2), and Class A foams are generally used on 3- dimensional solid fuel fires (Gann & Friedman, 2015). Gagnon (2008) suggests foam smothers, cools, insulates, and penetrates flammable and combustible liquids in order to extinguish them and that there are three types of foam: low-, medium-, and high-expansion, which have a greater effectiveness than straight water on some fires. High-expansion foams are primarily used on three-dimensional fires where the medium and low expansion foams are predominantly used on two-dimensional fires. The effectiveness of foam on the fire ground can be disrupted by high winds blowing the foam blanket away; high heat from the fire breaking down the foam blanket and vaporizing the water mixture in the foam, vapors or fluids from the spilled product breaking down the foam structure, or the firefighter not proportionately mixing the foam concentrate and water. Points to Ponder In the scenario below, did the additives improve firefighting performance? Did the wetting agent absorb heat, keeping Engine 5 safer from thermal insult? Did the wetting agent stay on the fuel it contacted longer than water alone? Did conditioning or wetting the walls, ceilings, and floors have any effect? Did conditioning cool the environment? Did it produce less steam and improve visibility for the firefighters?
Figure 2
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Conclusion Water, the oldest form of fire suppressant, is still the most common means of fire suppressant. Water extinguishes fire by cooling the fuel, lowering the temperature of fire, and absorbing enthalpy. Water is used in water-based sprinkler systems and by firefighters using handlines. Additives are mixed with water to improve effectiveness. These are thickeners, wetting agents, foam formers, film formers, and emulsifiers. Due to synthetics and other combustible materials in today’s fires, any method of suppression is critical to conserve property and save lives.
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. Bellis, M. (2019, February 11). A brief history of fire sprinklers. ThoughtCo. https://www.thoughtco.com/fire-
sprinkler-systems-4072210 Gagnon, R. M. (2008). Design of special hazard and fire alarm systems (2nd ed.). Delmar Learning. Gann, R. G., & Friedman, R. (2015). Principles of fire behavior and combustion (4th ed.). Jones & Bartlett
Learning. Innovating fire attack tactics. (2013, Summer). New Science Fire Safety.
https://newscience.ul.com/articles/innovating-fire-attack-tactics
Building on the Scenario The Incident Command (IC) just finished attending a demonstration on synthetic detergent hydrocarbon surfactant designed to reduce the surface tension of water and improve heat absorption and water penetration. The sales person gave the IC 10 gallons to try on a fire. IC ordered the introduction of the wetting agent to Engine 5’s handlines in hopes to increase the effectiveness of water. Tower 2 continued down the hallway with the down firefighter as Engine 5 opened the nozzle. The officer on Engine 5 attended the same demonstration and told the nozzle man to begin coating all the wall, ceiling, and floor surfaces hoping to effectively suppress vapor production. As they worked their way to the main fire, they continued applying the wetting agent in hopes that the water would penetrate to the seat of the fire. Under the weight of the smoke, the lead attack person applied the wetting agent to everything including the smoke when the officer yelled out, "We don't put water on smoke." The wetting agent seemed to work well on the upholstered chairs and couches. However, the fire continued to build with intense heat banking down around the firefighters. After the 10 gallons of wetting agent was used, command had all crews withdraw from the interior based on observations from the exterior. As Tower 2 was removing the injured firefighter, command requested a personnel accountability report (PAR). Upon completion of the PAR, Engine 2 did not report. Command, assuming the firefighters were missing, ordered the rapid intervention team (RIT) to search the last known area where Engine 2 was working. RIT quickly located one of the missing firefighters in the hallway on the second floor. The firefighter was disorientated and did not know which way to go from the heavy smoke conditions. The other firefighter (lieutenant) was found outside on Side “C”. The lieutenant stated his radio had quit working due to the extreme heat and water before becoming disorientated for a few minutes. He stated his crew member became anxious and stood up and left him. After trying to locate his crew member for a few minutes, he decided to escape the hostile fire and smoke conditions inside. Ambulances transported all of the firefighters to the hospital for burns and smoke inhalation. During the search and rescue efforts, severe fire conditions drove the RIT from their working position until Command reported the firefighters were accounted for. Eventually, the fire was extinguished after three alarms and thousands of gallons of water. Because of the fire injuries and scale of the fire, the state fire marshal ordered an investigation into the actions of those on the scene. National Institute of Standards and Technology (NIST) was requested to develop a series of fire dynamics simulations to examine fire behavior and combustion. The report indicated that conditions in the apartment created an environment that allowed the fire to grow rapidly. The temperature and oxygen-rich air from the wind gust, as well as the voids from the addition of the third floor, caused the fire to spread faster than the handlines could cool the compartmented area, resulting in total involvement.
FIR 2303, Fire Behavior and Combustion 5
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Kerber, S. (2012, July). Examination of the impact of ventilation and exterior suppression tactics on residential fires. Presentation with UL, NIST and the Fire Department of the City of New York.
Kerber, S. (2013). Study of the effectiveness of fire service vertical ventilation and suppression tactics in
single family homes. UL Fire Safety Research Institute. https://ulfirefightersafety.org/docs/UL-FSRI- 2010-DHS-Report_Comp.pdf
Lambert, K. (2014). Transitional attack. CFBT-BE. http://www.cfbt-
be.com/images/artikelen/artikel_21_ENG.pdf Sturzenbecker, M. J., Adams, B., & Burnside, E. (Eds.). (2016). Fire protection, detection, and suppression
systems (5th ed.). Fire Protection Publications.
Learning Activities (Nongraded) Nongraded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information. Conceptual thinking is a great way to study because it gives you a chance to process what you have learned and increases your ability to remember it. Review the case study below, and write one-two pages using the concepts learned in this unit to answer the questions following this case study.
You are responding for mutual aid to assist another fire department with a fire of an 8,000-gallon gasoline tanker carrying an unknown amount of product. The fire officer met you upon arrival, briefing you about the incident. The cab is fully involved, destroying any shipping papers that would confirm product identification. The fire officer told you that upon arrival they could see only two numbers on the placard—63. The fire officer lay a large diameter hose line and set up an unmanned monitor in attempts to knock down the fire. The ground monitor was isolated 150 feet from the spill. You noticed two 5-gallon containers of wetting agents that were empty next to the ground monitor. There were flammable liquids that were not ignited pooling on the roadway. The monitor’s application rate was set on 0.16 gpm/sq. ft.
Based on the scenario, what type of fuel was involved in the overturned tanker? What is the best agent for fighting this fire? Why? You may use various sources, including your textbook or other scholarly material; however, the point of this nongraded activity is for you to actively and skillfully conceptualize, apply, analyze, and evaluate the wetting agent used. If you have any questions or do not understand a concept, contact your professor for clarification.