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FIR 2303, Fire Behavior and Combustion 1

Course Learning Outcomes for Unit III Upon completion of this unit, students should be able to:

2. Categorize the components of fire. 2.1 Describe the process of combustion. 2.2 Identify oxidizers in a fire scenario.

3. Explain the properties of fire.

3.1 Explain flammability in terms of both fire properties and practical application. 3.2 Describe the non-flaming and flaming stages of fire.

Course/Unit Learning Outcomes

Learning Activity

2.1

Unit Lesson Chapter 6, pp. 77–94 Article: The Current Knowledge & Training Regarding Backdraft, Flashover, and Other Rapid Fire Progression Phenomena Article: Backdraft: Fire Science and Firefighting, a Literature Review Unit III Essay

2.2

Unit Lesson Chapter 6, pp. 77–94 Article: The Current Knowledge & Training Regarding Backdraft, Flashover, and Other Rapid Fire Progression Phenomena Article: Backdraft: Fire Science and Firefighting, a Literature Review Unit III Essay

3.1

Unit Lesson Chapter 6, pp. 77–94 Article: The Current Knowledge & Training Regarding Backdraft, Flashover, and Other Rapid Fire Progression Phenomena Article: Backdraft: Fire Science and Firefighting, a Literature Review Unit III Essay

3.2

Unit Lesson Chapter 6, pp. 77–94 Article: The Current Knowledge & Training Regarding Backdraft, Flashover, and Other Rapid Fire Progression Phenomena Article: Backdraft: Fire Science and Firefighting, a Literature Review Unit III Essay

Required Unit Resources Chapter 6: Combustion, Fire, and Flammability, pp. 77–94 In order to access the following resources, click the links below. These papers describe the experimental knowledge and literature reviews from smoke explosion research and compares the smoke explosion to the more familiar phenomena known as backdraft.

UNIT III STUDY GUIDE

Components of Fire

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Gorbett, G. E., & Hopkins, R. (2007, June). The current knowledge & training regarding backdraft, flashover, and other rapid fire progression phenomena. Paper presented at the meeting of the National Fire Protection Association World Safety Conference, Boston, MA, United States. http://www.globalfireresearch.com/reports/research/the-current-knowledge-training-regarding- backdraft-flashover-and-other-rapid-fire-progression-phenomena#.W6jb52hKi01

Please read sections 2.1 through 2.5.3 of the paper related to the backdraft phenomenon and the important factors of backdraft. Lambert, K. (2014, January). Backdraft: Fire science and firefighting, a literature review (Master’s paper).

CFBT-BE. http://www.cfbt-be.com/images/artikelen/LAMBERT_backdraft.pdf

Unit Lesson Review We covered matter as solid, liquid, and gas. These same three forms can undergo enthalpy changing to a chemical reaction producing intense heat and typically light. We covered the gasification of solids and aerosols found in soot as hydrocarbons and fibers. We reviewed the two methods of heat transfer as conduction and radiation. Even though several authors state there are three methods of heat transfer, we learned that convection is an independent mode of heat transfer. We looked at a charcoal grill going from the flames as radiant heat to the effect of wind in the form of a fan effecting the convection. We reviewed thermal conductivity and the effects on solids, liquids, and gases and their conductivity. We evaluated insulation qualities of thermally thick and thermally thin materials and what happens when those insulation qualities diminish. Components of Fire Combustion is the generation of substantive heat and often light described by several authors as an exothermic chemical reaction between a fuel and an oxidizer (Gann, & Friedman, 2015; International Fire Service Training Association [IFSTA], 2013). Several movies involving fire have portrayed the components of fire as a living organism. The movie Only the Brave showed fire as potentially uncontained and destructive acquiring an animal personality of a bear teasing and taunting firefighters running through the forest (Luckinbill et al. 2017). The 1991 movie Backdraft gives fire the appearance that it is alive and is intelligent, knowing when to hide or burst headfirst, devouring firefighters or others in its path. Writers such as Widen (n.d.) in Backdraft used descriptors like “smoke is like liquid lead,” “buffeting waves of flame in the ceiling,” “fire screams in manic anger,” “heaves a cloud of howling steam,” and “whirls back and bakes them like lobsters” to describe the backdraft phenomenon. Are the components of fire really like what we see in movies? Are the descriptors in movies a means to sensationalize fire? Could the descriptor “waves of flame” be flameover? Is “smoke like liquid lead” a rollover? Are these phrases accurate? Does it help you understand the fire phenomena in flameover, rollover, flashover, or even backdraft? Do you truly understand the differences between each of these phenomena or the components of fire? Gorbett and Pharr (2011) warn that fire changes drastically throughout the development until it reaches the fully developed phase. The authors even suggest that if firefighters misread the conditions of fire or anticipated fire conditions, it will lead to fatalities and injuries. In the fire academy, we learned combustion requires the four components of the fire tetrahedron:

1. fuel, 2. oxygen, 3. heat, and 4. chemical chain reaction.

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Even today, some fire instructors reference the fire triangle when describing combustion. However, should the fire triangle or even tetrahedron be another shape (Figure 1)? Should there be another side that is self- sustaining reaction? Smoldering? Is there more to combustion than fuel, heat, and oxygen? If self-sustaining reaction stops, the fire goes out, right? Nonflaming and Flaming Combustion Several authors referred to nonflaming combustion as smoldering that is a low- temperature, flameless form of combustion that slowly reacts (Gann, & Friedman, 2015; Gorbett & Pharr, 2011). In a structure fire, there are many solid materials that can sustain a smoldering reaction—including but not limited to cotton clothes, cotton fabric on furniture, organic fiber, synthetic foam, chairs or couches—until the conditions change, and flaming occurs.

You probably have seen fires where a cigarette was dropped on either a chair or mattress and smolders until firefighters take it outside. Normally, cigarettes in the nonflaming state produce gases insufficient to sustain flaming (Figure 2). For the cigarette to remain in the nonflaming state, heat, oxygen, and fuel must maintain a self-sustaining reaction in the release of heat to continue pyrolysis without reaching flaming (Figure 3). This occurs with anything that smolders, such as in the charcoal example in Unit II. In other words, if any one of these (heat, oxygen, or fuel) is altered, then flaming combustion may occur instead of smoldering (Figure 4). If a cigarette is dropped into the back of a chair (in the crack between the seat and back cushion), heat from the cigarette would be confined to that area allowing the smoldering state of the cigarette to transform into flaming combustion. Flaming combustion preheats the surrounding material (fabric and synthetic foam) emitting gases. Pyrolysis continues exposing the synthetic foam to sufficiently high heat to create the chemical reaction between oxygen and combustibles reaching the flaming stage. The porous structure of the foam increases the pyrolysis process with oxygen that is easily available in the foam and consequent heat transfer. This accelerates the process of the nonflaming combustion of the synthetic foam until the ignition

Figure 1

Figure 2

Figure 3 Figure 2

Figure 4

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process is reached. Many factors affect the pyrolysis process such as the effect of wind velocity, the ambient conditions inside of the room, and even the humidity levels. As we saw in Unit II with the charcoal grill, the introduction of wind from an open window, fan, or even an HVAC system could increase the velocity of the process. Flaming Combustion Flaming combustion involves gaseous fuel mixing with air, reacting with oxygen, and releasing heat that could lead to room flashover (Gann & Friedman, 2015). In each of these states, the fuel must gasify. However, with the solid, such as wood, the fuel goes through pyrolysis or, as some texts state, decomposition. Flaming in each of these states requires oxygen-rich air. In the ignition stage, the flaming will entrain oxygen to meet the demands of combustion. As seen with the cigarette and cotton fabric chair example (in Figure 4 above), the fire began in the smoldering state and progressed to flaming. Gann and Friedman (2015) stated smoldering is the most common state that develops into flaming combustion. The smoldering cigarette occurred in the cotton fabric until the cotton fabric reached flaming combustion allowing the synthetic foam to become involved. Flaming combustion in the example was well ventilated and began to consume all the fresh air in the room then pulling air from open doors and window, as well as any opening in the structure (Figure 5). Under-Ventilated Flaming

The well-ventilated flaming state continues until conditions restrict oxygen and becomes under-ventilated (Figure 6). As flaming reaches the under-ventilated condition, several phenomena can occur while the air in the room remains very low and normally clear. The upper layers become radiant energy so intense it can ignite any combustible in its path, skimming across the surface of the ceiling almost in slow motion. Several authors describe this as flameover or rollover.

Flameover or Rollover Dunn (1999) suggests flameover is the abrupt spread of flame across the surface ceiling and any painted or covered surface that will sustain combustion (Figure 7). Whereas, National Fire Protection Association (NFPA, 2004) suggests flameover is unburned fuel that has accumulated in layers at the ceiling in sufficient concentration to ignite. An even

Figure 5

Figure 6

Figure 7

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simpler definition is all the combustibles at the ceiling level are aflame (Gann & Friedman, 2015). Flashover Avillo (2008) suggests flashover is a sudden transition in the growth stage of fire to fully developed fire. The initial heat with a flashover in a compartment fire is by convection, and later it becomes radiant energy transferring heat to any combustible material for a total surface involvement. Several authors suggest a flashover must reach approximately 1,000 to 1,200 °F (Avillo, 2008; Dunn, 1992). A simple description would be a flashover occurs when burning gases push out the openings (normally doors or windows) in a compartment at rapid velocity until every combustible surface within the compartment, becomes ignited. Many instructors have stated that flashover will occur within four to six minutes; however, flashover may never occur in fully involved structures. It requires sufficient heat and energy, as well as sufficient oxygen to develop flashover conditions. Dunn (1992) describes flashover as the explosion of a smoke-filled room into flame. He later discusses that flashover occurs after rollover. Dunn suggested there is an intermittent generation of flame seen throughout the smoke at the upper ceiling level just before flashover occurs. Backdraft or Smoke Explosion

There are many publications that are not technically accurate or even combine the phenomena into one definition (Gorbett & Hopkins, 2007). There are many videos of firefighters making entry into hostile fire environments with multiple signs of the backdraft phenomena. Why? Is it the lack of knowledge? Is it the lack of situational awareness? Are firefighters focused on extinguishment only? Is it complacency? Has backdraft been romanticized in the media, movies, and

TV episodes to the point firefighters do not believe the dangers? From the early 1900s, literature defined backdrafts as smoke explosions. Crosby et al. (1935) described smoke explosion in terms of a backdraft. In 1991, Brennen (2007) described smoke explosion as not being as forceful as a backdraft. As recent as 2007, some articles referenced smoke explosion as a large buildup of super-heated smoke that ignites with explosion-type force. These same articles even referenced it as white smoke (Sutherland, 1999). Fleischmann and Chen (2013) describe smoke explosion as fuel rich combustible gases mixed with available oxygen within a compartment where oxygen-rich air is leaking in and combustible gases are leaking out (Figure 8). However, the cold, oxygen-rich air does not reach the seat of the fire, leaving the fire in a smoldering state until oxygen levels build and reach the fire. The authors established two different definitions for smoke explosion and backdraft, although they are similar. Then what is a backdraft? Fleischmann and Chen (2013) describe backdraft as hot, fuel-rich flaming in a closed compartment where insufficient oxygen allows unburned fuel to accumulate in layers descending around the fire until oxygen-rich air rushes in creating an explosion (Figure 9). Gorbett and Pharr (2011) describe backdraft as the rapid flame spread involving fuels that have dispersed in air and burning with explosive force. IFSTA (2013) suggests backdraft is sufficient heat in a compartment where temperatures of combustible products reached their

Figure 8

Figure 9

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ignition temperatures without igniting until sufficient oxygen is available to support combustion. Whether one defines the phenomena as a smoke explosion or a backdraft, the flame propagation of the fire consumes the available oxygen, accumulating unburned fuel and transitions into the decay phase with high heat until the introduction of oxygen-rich air. Points to Ponder In the scenario outlined in the sidebar to the right, what happened? Did Engine 5 see a backdraft, flameover, or a rollover? Gorbett and Pharr (2011), warn that the failure to understand the differences leads to fatalities and injuries of firefighters. The authors continue to warn that flameover, backdraft and flashover are the most commonly misunderstood phenomena. Either one of these phenomena can change rapidly throughout flaming combustion resulting in devastation.

Conclusion Combustion is an exothermic reaction requiring fuel and an oxidizer, which produces heat significant enough to create flaming. Combustion can be in nonflaming and flaming stages. In the nonflaming stage, the increase of oxygen-rich air or heat will result in flaming. If the fuel is suprerheated without enough oxygen-rich air then it could result in a smoke explosion or even a backdraft. Smoke explosion is the sudden unexpected explosion from the result of a no ventilation process introducing oxygen-rich air into the compartment. Smoke explosion occurs from leakage of oxygen-rich air into the compartment. Backdraft is the sudden introduction of oxygen-rich air from some type of ventilation process, such as a window breaking from the suprerheated air, firefighters venting a window, or opening a door. The opening allows oxygen-rich air to reach the fire and ignites the suprerheated fuel suspended in smoke with an explosive force. Understanding the components of fire will help firefighters reduce the potential hazards of a hostile fire.

References Avillo, A. (2008). Fireground strategies (2nd ed.). PennWell Corporation. Brennan, T. F. (2007). Tom Brennan’s random thoughts. PennWell Corporation. Crosby, E. U., Fiske, H. A., & Forster, H. W. (1935). NFPA handbook of fire protection (8th ed.). National Fire

Protection Association.

Building on the Scenario The firefighters in apartment 2-B continued operating the nozzle without making any headway. Conditions continued to get unbearable and the firefighters backed out into another room in 2-B. Command continued to watch the turbulent black and brownish smoke issuing from the window and reaching the eaves. Command advised Engine 2 to withdraw from the apartment and the Lieutenant convinced command they had a handle on the fire and were making an aggressive knockdown and continued to remain deep into the structure where fire was still visible overhead using the TIC (thermal imaging camera). The smoke was in layers across the ceiling, which appeared as residual smoke mixed with smoke from the fire; however, no flaming was visible to Engine 2’s firefighters. This was Engine 2’s Lieutenant’s first fire, and he did not want anyone to say he could not handle the heat. Tower 2 reported conditions in 2-H were deteriorating with tremendous heat. Engine 5 was pushing down the hallway pulling a backup line noting the smoke appeared to be lazier and maybe lighter in color than in the stairwell. They noted heat was still high as it was radiating from the walls. Engine 5 could hear crackling in the walls as they opened the door in apartment 2-C to see oxygen starved flames come to life almost simultaneously with ignition.

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Dunn, V. (1992). Safety and survival on the fireground. PennWell Corporation. Dunn, V. (1999). Command and control of fires and emergencies. Fire Engineering Books & Videos. Fleischmann, C. M., & Chen, Z. (2013). Defining the difference between backdraft and smoke explosions.

Procedia Engineering, 62(2013), 324–330. https://ac.els-cdn.com/S1877705813012538/1-s2.0- S1877705813012538-main.pdf?_tid=234edf73-9637-4d67-ba59- 1644cf1eb62c&acdnat=1531446979_9767c51493457785303632b5e0aa4747

Gann, R. G., & Friedman, R. (2015). Principles of fire behavior and combustion (4th ed.). Jones & Bartlett

Learning. Gorbett, G. E., & Hopkins, R. (2007, June). The current knowledge & training regarding backdraft, flashover,

and other rapid fire progression phenomena. Paper presented at the meeting of the National Fire Protection Association World Safety Conference, Boston, MA, United States. https://ssem.eku.edu/sites/ssem.eku.edu/files/gorbett_-_the_current_knowledge_training.pdf

Gorbett, G. E., & Pharr, J. L. (2011). Fire dynamics. Pearson. International Fire Service Training Association. (2013). Essentials of firefighting (6th ed.). Fire Protection

Publications. Luckinbill, T., di Bonaventura, L., Ostroff, D. (Producers), & Kosinski, J. (Director). (2017). Only the brave

[Motion Picture]. United States: Sony Pictures Entertainment. National Fire Protection Association. (2004). NFPA 921: Guide for fire and explosion investigation. Sutherland, B. J. (1999, March). Smoke explosions (Fire Engineering Research Report No. 99/15). Fire

Tactics. http://www.firetactics.com/Smoke,%20Sutherland.pdf Widen, G. (n.d.). Backdraft [Screenplay shooting draft]. IMSDb. http://www.imsdb.com/scripts/Backdraft.html

Suggested Unit Resources In order to access the following resources, click the links below. As you view these videos, remember firefighters work in uncontrolled environments during emergency situations. Some of the tactics do not follow Fire and Emergency Services Higher Education (FESHE) curriculum guidelines and outcomes for incident command, scene size-up, or fire attack. This course is about fire behavior and combustion. The purpose of viewing these videos is to watch combustion as an exothermic chemical reaction between a fuel and an oxidizer resulting in the generation of substantive heat and often light. In addition, understand for a fire to spread, some of the enthalpy from the ignition region must heat unburned material to a temperature at which it can burn, whether it leads to backdraft, flameover, or flashover, or not. This video is of a house fire in East Houston, Texas, which shows a backdraft. The video is raw footage and the hope is to observe the conditions that lead to a backdraft. Focus on the smoke colors and flaming. There is no transcript for this video as there is no narration. TheBravestOnline. (2011, November 16). East Houston, Texas backdraft the bravest online [Video].

YouTube. https://www.youtube.com/watch?v=TB733ALC9gw

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This video is a violent explosion that occurred after a hole was cut that blew an officers helmet off his head and blew the leaves in the lawn. Forward the video to 5:30–6:30 to observe the backdraft. There is no transcript for this video as there is no narration. mabas21. (2012, February 17). Flashover or backdraft occurs while crews are in a working house fire in New

Chicago [Video]. YouTube. https://www.youtube.com/watch?v=HfMZxEwUuUI This video starts off with a scene from the movie Backdraft (1991) and continues with multiple backdraft and flashover clips. There is no transcript for this video as there is no narration. Van Svenson, G. (2008, February 13). Backdraft & flashover [Video]. YouTube.

https://www.youtube.com/watch?v=InrS4Fdndr4 This video is an animation of what happens in a backdraft with the description. iaaifireinvestigator. (2011, November 2). What happens in a backdraft? [Video]. YouTube.

https://www.youtube.com/watch?v=v6CFt74ktBw Click here to access the transcript for this video.

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. 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. For this activity, you are asked to review the sticky note presentation by clicking on the image of sticky notes, or here. We often use sticky notes to remind us of things to do or to even study for an exam. As you review the presentation, reflect on the concepts you have learned during your readings. What do you understand completely? What phrase does not quite make sense? The purpose of this assignment is to provide you with the opportunity to reflect on the material you have read.

If you have any questions or do not understand a concept, contact your professor for clarification.