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The Science of Fire (Old)
Fire can be one of nature’s most devastating natural forces. However it can also be one of the most scientific. I am almost certain that almost any normal person doesn’t know a large amount about fire, other than the fact that burns. There are many different aspects of fire. The first aspect is how fires ignite. This includes the elements need for fire to exist. Next, the next bit of information about fire is the stages of fire. There are four stages; these include ignition, growth, fully developed and the decay stage. Thirdly, significant fire events also are aspects of fire. Mainly, there are three different events, thermal layering, flashover and rollover, as well as back draft. There are also many different types of fires. These include, class A, B, C and D. Each type is different and is classified by what starts the fires. Finally, there are also different heat sources that can create fire. These main heat sources are chemical, and mechanical. As you can see there are a lot of different aspects of fire.
For fire to exist, you must have three basic elements. Without one of these elements, the fire won’t ignite or will just go out. The first component necessary is heat. Next, fuel is another element required for fire to exist. Whether the fuel is paper, wood or some type of gas, without something to burn there would be no fire. Hence that is why fuel is so necessary for fire to exist. The third element of fire is oxygen. Just like humans. Fire needs oxygen to exist. If oxygen would be cut off, the fire would eventually extinguish itself. As an example, if there would be a frying pan of grease on fire, by putting a lid on the pan, oxygen would be removed. In turn, the fire would then smother itself from losing oxygen. However, if the lid is removed before the fire is completely extinguished, the fire would then rapidly rekindle because of a rush of oxygen. (Essentials of Firefighters and Emergency Response, Pg 75)
In previous years, there has been a diagram of the elements of fire known as the fire triangle. This showed all three elements in a simple triangle. The triangle was chosen because it has three sides, and there are three elements of fire. However, through recent research, scientists have discovered that there is another element of fire. This fourth element is a chemical reaction. Now the fire triangle was no longer able to be used, this meant that they had to create a new diagram, the Fire Tetrahedron. (Essentials of Firefighters and Emergency Response, Pg 77)
(http://en.wikipedia.org/wiki/Fire_tetrahedron#Fire_tetrahedron)
Along the lines of the fire tetrahedron, heat is one of the elements for fire to exist. There are two main heat sources that can create fire when the proper elements exist. The first heat source is chemical. This is the most common heat source for fires. Next, mechanical heat is common in industry which is caused by friction.
To begin, chemical heat is the most common heat source. This is the most common, simply because when fire burns, it gives off heat as a product. Also, every fire starts with a chemical reaction according to the fire tetrahedron. The second most common heat source is mechanical. This type of heat is created by friction of materials rubbing together. It is a popular cause of fire in the industry because many industrial plants have machinery that have moving parts. These parts generate heat and can often start fires if not properly lubricated and cooled. The simplest way to extinguish a fire started by friction, is to just remove the friction, or turn off the machine. (Essentials of Firefighters and Emergency Response, Pg 83)
Fire also has four different stages. These stages, include ignition, growth, fully developed and the decay stage. Each stage is different in its own way. The first stage of fire is the ignition stage. This stage is the beginning of the fire, hence the name, ignition. The materials, or fuel, begins to heat up and combust. Also this is when all the elements from the fire tetrahedron come together, the chemical reaction, heat, fuel and oxygen. Once ignited, the fire is normally very small, and begins the next stage.
The stage succeeding the ignition stage is known as the growth stage. From the very beginning the fire starts growing and developing but this varies depending on the amount of oxygen and fuel. It also depends on the type of container that the fire is in and whether or not it is insulated. (Quintiere, James G. Pg 82)
The third stage of fire is the stage when the fire is fully developed. This means that all the contents within the fire are actively involved in the process. Should this fire happen to be within a home or any other type of structure, all the room contents would be on fire such as furniture. If the fire is outside, perhaps in a forest or a field, this means that all the burnable fuel or materials within reach of the fire are involved. (Quintiere, James G. Pg 83)
The final stage of the fire is called the decay stage. This is the stage when almost all, or all, of the burnable material or fuel has been used up or burned by the fire. This also leads to the fire beginning to extinguish itself. This is a perfect example of how the fire tetrahedron works as well. Since you need all for elements for fire to exist, if all the fuel is used up, then the fire goes out. By taking away an element, such as the fuel of the fire, the fire is extinguished. (Quintiere, James G. Pg 84)
During these stages of fires, mainly the growth stage, there are three different fire events. The first event is called thermal layering, which is caused by the gases produced by the fire. Next, flash over and roll over can also occur, which are caused by gases and heat. Finally, back draft, not the movie, is caused by losing an element of fire.
Thermal layering, is an event just like the name suggests, layering of the air above the fire. This is caused when the gases produced by the fire rise above. These gases will continue to increase in the building while trying to find a way out. (Carter, Harry. Pg 75)
Secondly, flash over and roll are the most known fire events. Flashover occurs when all the contents in the room ignite at the same time. This will create a lot of heat and fire and occurs in just seconds. For firefighters, this can be very dangerous because the heat can overwhelm the firefighters and could lead to death. Roll over is related to thermal layering in that it is when the gases above the fire ignite. This causes fire to travel across the ceiling. This is also dangerous to firefighters because the fire can move over top of them and travel down a wall behind them. This often blocks the firefighters exits to be blocked. (Carter, Harry. Pg 75)
Lastly, back draft is another common fire event. This is caused by the fire using up all of a certain element, and then it rapidly renews the element it lost from another source. For example, if there is a fire in a room where all the doors and windows are shut, eventually the fire will run out of oxygen, an important element to fire. If someone were to open the door during the period where the fire is starting to smother itself due to the lack of oxygen, the fire will rapidly reignite due to the rush of oxygen into the room. (Carter, Harry. Pg 76)
Finally, there are four different classes of fires. Fires are classified by the fuel that is being burned. The classes are simple, there are class A fires, class B, class C and class D. Each different in respect of the fuel that they burn. They all must be extinguished in different ways as well. Class A fires are some of the most common fires though.
The most common class of fire is class A. This fires are fires that just burn regular every day combustible materials such as wood, paper, fabric, etc. These fires can be extinguished with just plain water due to the type of fuel that is burning. The materials don’t burn at really high temperatures so the water is enough to remove the heat so that the fire goes out. (Fire Protection Handbook. Pg 42)
Next, class B is another type of common fires. These fires are fires that are fueled by liquids and gases, such as propane, or gasoline. Unlike class A fires, water will not do the job of extinguishing these fires. The key to extinguishing a fire of this class is to smother the fire and cut it off from oxygen. To do this, firefighters use a water based foam to smother the flames. If a you were to try and extinguish a liquid fuel fire with water the flames would just spread because the water would push the fuel around spreading it. (Fire Protection Handbook. Pg 42-43)
The third class of fire is fueled by electricity. These are class C fires and are also very common especially in households. These fires are simply caused by the electricity causing heat, or an electrical device malfunctioning. To extinguish this type of fire just remove the power source. This removes the fuel of the fire. (Fire Protection Handbook. Pg 44)
Lastly, class D fires are not as common as A, B or C. These fires are metal fires the burn at extremely high temperatures. The most common metals that burn include magnesium, titanium, zirconium, sodium and potassium. Fires of this nature can also be blinding to the naked eye. Class D fires also cannot be extinguished with water because the water can actually sometimes create a chemical reaction between the water and metal on fire. (Fire Protection Handbook. Pg 45)
In conclusion, fire can be a very complicated form of nature. From the elements that create it and the research that goes into it. Fire cannot exist without all four of its elements. Those being a chemical reaction, oxygen, fuel and heat. There are also four different stages of fire. The first one being the ignition stage, when the fire is just starting of course. The second stage is the growth stage, which is followed by the fully developed stage. This is when all the combustible materials are now involved in the fire. Lastly, the decay stage, which is when the fire is beginning to extinguish itself due to losing an element required for existence. There are also 3 main fire events as well, these being thermal layering, roll over and flash over, and back draft. Also, along with the fire triangle and tetrahedron, they suggest that heat is required for fire to exist. Heat comes from two main sources, chemical and mechanical. Lastly, there are four different classes of fires, each different in their own way, whether it’s the materials being burned or how they have to be extinguished. As you can see there are many different aspects of fire. That is why it can be one of the most scientific natural forces, as well as one of the most devastating. You never know when it will occur and sometimes it can’t be avoided.
Works Cited
Carter, Harry. Firefighting Strategy and Tactics. Stillwater, OK: Fire Protection Publications, 1998.
The Firefighter's Handbook: Essentials of Firefighters and Emergency Response, Second Edition. Clifton Park, NY: Delmar, 2005.
Fire Protection Handbook. 18th ed. Quincy, MA: National Fire Protection Agency, 1997.
"Fire Triangle." Wikipedia. 29 Feb. 2008. 30 Feb. 2008
a href="http://en.wikipedia.org/wiki/Fire_tetrahedron#Fire_tetrahedron">http://en.wikipedia.org/wiki/Fire_tetrahedron#Fire_tetrahedron>.
Quintiere, James G. Principles of Fire Behavior,. Clifton Park, NY: Delmar Learning, a Part of the Thomson Corporation, 1998.
For fire to exist, you must have three basic elements. Without one of these elements, the fire won’t ignite or will just go out. The first component necessary is heat. Next, fuel is another element required for fire to exist. Whether the fuel is paper, wood or some type of gas, without something to burn there would be no fire. Hence that is why fuel is so necessary for fire to exist. The third element of fire is oxygen. Just like humans. Fire needs oxygen to exist. If oxygen would be cut off, the fire would eventually extinguish itself. As an example, if there would be a frying pan of grease on fire, by putting a lid on the pan, oxygen would be removed. In turn, the fire would then smother itself from losing oxygen. However, if the lid is removed before the fire is completely extinguished, the fire would then rapidly rekindle because of a rush of oxygen. (Essentials of Firefighters and Emergency Response, Pg 75)
In previous years, there has been a diagram of the elements of fire known as the fire triangle. This showed all three elements in a simple triangle. The triangle was chosen because it has three sides, and there are three elements of fire. However, through recent research, scientists have discovered that there is another element of fire. This fourth element is a chemical reaction. Now the fire triangle was no longer able to be used, this meant that they had to create a new diagram, the Fire Tetrahedron. (Essentials of Firefighters and Emergency Response, Pg 77)
(http://en.wikipedia.org/wiki/Fire_tetrahedron#Fire_tetrahedron)
Along the lines of the fire tetrahedron, heat is one of the elements for fire to exist. There are two main heat sources that can create fire when the proper elements exist. The first heat source is chemical. This is the most common heat source for fires. Next, mechanical heat is common in industry which is caused by friction.
To begin, chemical heat is the most common heat source. This is the most common, simply because when fire burns, it gives off heat as a product. Also, every fire starts with a chemical reaction according to the fire tetrahedron. The second most common heat source is mechanical. This type of heat is created by friction of materials rubbing together. It is a popular cause of fire in the industry because many industrial plants have machinery that have moving parts. These parts generate heat and can often start fires if not properly lubricated and cooled. The simplest way to extinguish a fire started by friction, is to just remove the friction, or turn off the machine. (Essentials of Firefighters and Emergency Response, Pg 83)
Fire also has four different stages. These stages, include ignition, growth, fully developed and the decay stage. Each stage is different in its own way. The first stage of fire is the ignition stage. This stage is the beginning of the fire, hence the name, ignition. The materials, or fuel, begins to heat up and combust. Also this is when all the elements from the fire tetrahedron come together, the chemical reaction, heat, fuel and oxygen. Once ignited, the fire is normally very small, and begins the next stage.
The stage succeeding the ignition stage is known as the growth stage. From the very beginning the fire starts growing and developing but this varies depending on the amount of oxygen and fuel. It also depends on the type of container that the fire is in and whether or not it is insulated. (Quintiere, James G. Pg 82)
The third stage of fire is the stage when the fire is fully developed. This means that all the contents within the fire are actively involved in the process. Should this fire happen to be within a home or any other type of structure, all the room contents would be on fire such as furniture. If the fire is outside, perhaps in a forest or a field, this means that all the burnable fuel or materials within reach of the fire are involved. (Quintiere, James G. Pg 83)
The final stage of the fire is called the decay stage. This is the stage when almost all, or all, of the burnable material or fuel has been used up or burned by the fire. This also leads to the fire beginning to extinguish itself. This is a perfect example of how the fire tetrahedron works as well. Since you need all for elements for fire to exist, if all the fuel is used up, then the fire goes out. By taking away an element, such as the fuel of the fire, the fire is extinguished. (Quintiere, James G. Pg 84)
During these stages of fires, mainly the growth stage, there are three different fire events. The first event is called thermal layering, which is caused by the gases produced by the fire. Next, flash over and roll over can also occur, which are caused by gases and heat. Finally, back draft, not the movie, is caused by losing an element of fire.
Thermal layering, is an event just like the name suggests, layering of the air above the fire. This is caused when the gases produced by the fire rise above. These gases will continue to increase in the building while trying to find a way out. (Carter, Harry. Pg 75)
Secondly, flash over and roll are the most known fire events. Flashover occurs when all the contents in the room ignite at the same time. This will create a lot of heat and fire and occurs in just seconds. For firefighters, this can be very dangerous because the heat can overwhelm the firefighters and could lead to death. Roll over is related to thermal layering in that it is when the gases above the fire ignite. This causes fire to travel across the ceiling. This is also dangerous to firefighters because the fire can move over top of them and travel down a wall behind them. This often blocks the firefighters exits to be blocked. (Carter, Harry. Pg 75)
Lastly, back draft is another common fire event. This is caused by the fire using up all of a certain element, and then it rapidly renews the element it lost from another source. For example, if there is a fire in a room where all the doors and windows are shut, eventually the fire will run out of oxygen, an important element to fire. If someone were to open the door during the period where the fire is starting to smother itself due to the lack of oxygen, the fire will rapidly reignite due to the rush of oxygen into the room. (Carter, Harry. Pg 76)
Finally, there are four different classes of fires. Fires are classified by the fuel that is being burned. The classes are simple, there are class A fires, class B, class C and class D. Each different in respect of the fuel that they burn. They all must be extinguished in different ways as well. Class A fires are some of the most common fires though.
The most common class of fire is class A. This fires are fires that just burn regular every day combustible materials such as wood, paper, fabric, etc. These fires can be extinguished with just plain water due to the type of fuel that is burning. The materials don’t burn at really high temperatures so the water is enough to remove the heat so that the fire goes out. (Fire Protection Handbook. Pg 42)
Next, class B is another type of common fires. These fires are fires that are fueled by liquids and gases, such as propane, or gasoline. Unlike class A fires, water will not do the job of extinguishing these fires. The key to extinguishing a fire of this class is to smother the fire and cut it off from oxygen. To do this, firefighters use a water based foam to smother the flames. If a you were to try and extinguish a liquid fuel fire with water the flames would just spread because the water would push the fuel around spreading it. (Fire Protection Handbook. Pg 42-43)
The third class of fire is fueled by electricity. These are class C fires and are also very common especially in households. These fires are simply caused by the electricity causing heat, or an electrical device malfunctioning. To extinguish this type of fire just remove the power source. This removes the fuel of the fire. (Fire Protection Handbook. Pg 44)
Lastly, class D fires are not as common as A, B or C. These fires are metal fires the burn at extremely high temperatures. The most common metals that burn include magnesium, titanium, zirconium, sodium and potassium. Fires of this nature can also be blinding to the naked eye. Class D fires also cannot be extinguished with water because the water can actually sometimes create a chemical reaction between the water and metal on fire. (Fire Protection Handbook. Pg 45)
In conclusion, fire can be a very complicated form of nature. From the elements that create it and the research that goes into it. Fire cannot exist without all four of its elements. Those being a chemical reaction, oxygen, fuel and heat. There are also four different stages of fire. The first one being the ignition stage, when the fire is just starting of course. The second stage is the growth stage, which is followed by the fully developed stage. This is when all the combustible materials are now involved in the fire. Lastly, the decay stage, which is when the fire is beginning to extinguish itself due to losing an element required for existence. There are also 3 main fire events as well, these being thermal layering, roll over and flash over, and back draft. Also, along with the fire triangle and tetrahedron, they suggest that heat is required for fire to exist. Heat comes from two main sources, chemical and mechanical. Lastly, there are four different classes of fires, each different in their own way, whether it’s the materials being burned or how they have to be extinguished. As you can see there are many different aspects of fire. That is why it can be one of the most scientific natural forces, as well as one of the most devastating. You never know when it will occur and sometimes it can’t be avoided.
Works Cited
Carter, Harry. Firefighting Strategy and Tactics. Stillwater, OK: Fire Protection Publications, 1998.
The Firefighter's Handbook: Essentials of Firefighters and Emergency Response, Second Edition. Clifton Park, NY: Delmar, 2005.
Fire Protection Handbook. 18th ed. Quincy, MA: National Fire Protection Agency, 1997.
"Fire Triangle." Wikipedia. 29 Feb. 2008. 30 Feb. 2008
a href="http://en.wikipedia.org/wiki/Fire_tetrahedron#Fire_tetrahedron">http://en.wikipedia.org/wiki/Fire_tetrahedron#Fire_tetrahedron>.
Quintiere, James G. Principles of Fire Behavior,. Clifton Park, NY: Delmar Learning, a Part of the Thomson Corporation, 1998.
Add a Comment
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Comment by Ben Waller on December 23, 2009 at 12:05am
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Sean,
Backdrafts are very uncommon events. Like Tiger, I've survived one and it it the only one I've seen in a3435-year career. I and my crew were fooled by the fact that fire was vented through the roof of a single-story, slab-foundation farmhouse. The fire was in the rear, with heavy smoke in the front. We thought that the entire structure was vented, but there was an interior room between the living room iin the front and the main body in the rear. When I opened the door to what I thought was the fire room, I was surprised by the big inrush of air and the immediate tumbling sensation as I was blown out of the house and into the front yard. If I had not been a) wearing an experimental nomex ensemble that included a jumpsuit, the first flash hood in my department, and full aramid gear, and b) been directly in line with the exterior door, I probably would have not survived.
My gear was so badly damaged that all of it was thrown away. I received small facial burns from the hot rubber at the edge of my mask, but no serious injury.
What happened to my backup firefighter? He was was a little slow and was masking up in the yard when I basically landed on him in the yard. (This was waaaaay before the 2-in, 2-out rule)
Most potential backdraft situations are pretty easy to recognize, but the ones like the one that almost nailed me are tricky, because the signs are hidden in the smoke and fire from the rest of the structure.
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Comment by Tiger Schmittendorf on December 22, 2009 at 11:51pm
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Added that comment to "My Stories" at www.runtothecurb.com.
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I actually survived a backdraft.
It was at a fire at a woodworking store and shop some 20+ years ago.
We had made entry through the rear building door. I was on the nozzle, about 15 ft. inside the building.
Just like it's often described, it got real dark and real quiet, real quick. The fire had been "dormant" and with just the right mixture of ventilation, it exploded.
The only thing that saved me was when I turned to watch my partner run. I landed about 15 ft. outside the building in the snow. Not knowing I was outside, I started crawling until someone picked me up by my airpack and dusted me off.
The explosion burned the hair off the back of my head. (We weren't wearing hoods yet.) It also took two guys, who were each literally three times my weight, and tossed them out the front window nearly into the street.
It's an experience I've never forgotten.
Stay safe. Train often.
(Oops. I think I accidently just told a story...)
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Comment by Sean Miller on December 21, 2009 at 2:26pm
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I never witnessed a flashover yet, but I've only been in the service for a few years...
I would like to go in a flashover simulator sometime though.
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Comment by Art "ChiefReason" Goodrich on December 21, 2009 at 2:15pm
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Sean:
It was a good article.
I was only pointing out that it is common to confuse the two phenomenons.
In all my years on the department, I did not see ONE backdraft.
However; I did get to witness flashovers.
Running a rural department, you get there most of the time just in time to see flashover.
Makes your choice of tactics much easier at that point.
Tomorrow, Dec. 22nd will make the tenth anniversary of the Keokuk, IA tragedy where three firefighters died in a flashover. I have a blog entitled Interview with Chief Mark Wessel that I will put up tomorrow in their memory, but the NIOSH report discusses the flashover that killed them.
Art
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Well I wrote this in my Junior year of highschool, I still had it, and got a good grade so I thought i'd post it.
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I respectfully disagree that backdraft "is a common fire event".
I happens rarely.
Like many, perhaps you are confusing backdraft with flashover.
TCSS.
Art
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