Chapter 5: Fire Behavior Flashcards
In the British System (Which is what we use) distance is measured in?
Liquid volume is measured in?
Temperature is measured in?
Pressure is measured in?
- Feet & Inches
- Gallons
- Degrees Fahrenheit
- Pounds per square inch
In the Metric System, distance is measured in?
Liquid is measured in?
Temperature is measured in?
Pressure is measured in?
- Meters
- Liters
- Degrees Celsius
- Pascals or Kilopascals
Matter is made up of atoms and molecules. What are the three stages in which matter exist?
Solid: A material that has three dimensions and is firm in substance, such as wood.
Liquid: A fluid (such as water) that has no independent shape, but has a definite volume and does not expand indefinitely and that is only slightly compressible.
Gas: The physical state of a substance that has no shape or volume of its own and will expand to take the shape and volume of the container or enclosure it occupies (like propane).
What is a Fuel?
Materials that store energy. Think of the vast amount of heat that is released during a fire. The energy released in the form of heat and light has been stored in the fuel before it is burned. The release of the energy in a gallon of gasoline, for example, can move a car many miles down the road. Many common household materials such as computers, TV’s, furniture and carpets, consist of fuels that will burn under the right conditions.
There are five types of energies, what are they?
- Chemical Energy
- Mechanical Energy
- Electrical Energy
- Light Energy
- Nuclear Energy
What is a Chemical Energy?
Energy created by a chemical reaction. Some chemical reactions produce or give off heat (Exothermic) and others absorb heat (Endothermic). The combustion process (Fire) is an example of an exothermic reaction, because it releases heat energy. Ice cubes melting (absorbing heat) is an example of an endothermic reaction. Most chemical reactions occur because bonds are established between two substances or bonds are broken as two substances are chemically separated. Heat is produced whenever oxygen combines with a combustible material. If the reaction occurs slowly in a well ventilated area, the heat is released harmlessly into the air. If the reaction occurs rapidly or within an enclosed space, the mixture can be heated to its Ignition Temperature and can begin to burn.
What is a Exothermic?
What is an Endothermic?
Chemical reactions that result in the release of energy in the form of heat. It gives off heat (Such a Fire).
Chemical reactions that absorbs heat or requires heat to be added (Such as Ice).
What is a Ignition Temperature?
The minimal temperature at which a fuel, when heated, will ignite in the presence of air and continue to burn. Fire is an example of energy being released as a result of a chemical reaction. An example of this occurs when a bundle of rags soaked with linseed oil releases enough heat through oxidation causing the rags to ignite spontaneously.
What is a Mechanical Energy?
Mechanical energy is converted to heat when two materials rub against each other and create friction. Heat is also produced when mechanical energy is used to compress air in a compressor.
What is a Electrical Energy?
Heat that is produced by electricity. Electrical energy is converted to heat energy in several ways. For example, electricity produces heat when it flows through a wire or any other conductive material. The greater the flow of electricity and the greater the resistance of material, the greater the amount of heat produced. Examples of electrical energies that can produce enough heat to start a fire is electric heating elements, overloaded wires, batteries etc.
What is a Light Energy?
Light energy is produced by electromagnetic waves packaged in discrete bundles called photons. This energy travels as thermal radiation, a form of heat. When the light energy is hot enough, it can sometimes be seen in the form of visible light. One example of light energy is the radiant energy we receive from the sun. We think of candles, fires, light bulbs and lasers as forms of light energy. Recognize that while these produce light, they also produce heat. They transfer most of their heat via convection or radiation. If they are touching something, they also transfer heat using conduction. If light energy is of a frequency that we cannot see, the energy may be felt as heat but not seen as visible light.
What is a Nuclear Energy?
Created by splitting the nucleus of an atom into two smaller nuclei (nuclear fission) or by combining two small nuclei into one large nucleus (fission). Nuclear reactions release large amounts of energy in the form of heat. These reactions can be controlled as in a nuclear power plant or controlled as in an atomic bomb explosion. Nuclear energy is stored in radioactive materials and converted to electricity by nuclear power generating stations.
What does the law of conservation of energy states?
States that energy cannot be created or destroyed by ordinary means. Energy can however, be converted from one form to another. Think of an automobile, chemical energy in the gasoline is converted to mechanical energy when the car moved down the road. When you press the breaks, the mechanical energy is converted into heat energy by the friction between the wheel rotators and break pads.
What is the difference between Oxidation, combustion and pyrolysis?
Oxidation: The process in which oxygen combined chemically with another substance to create a new compound. For example, steel that is exposed to oxygen results in rust. The process of oxidation can be very slow. It can take years for oxidation to become evident. Slow oxidation does not produce easily measurable heat.
Combustion: By contrast, combustion is a rapid chemical process in which the combination of a substance with oxygen produces heat and light. For FF, combustion and fire can be used interchangeably.
Pyrolysis: The process that liberates gaseous fuel vapors, due to the heating of a solid fuel. Pyrolysis is evident when wood is heated sufficiently and breaks down into vapors and char (Fig 5.5).
The difference between Combustion and Pyrolysis’s is that combustion is done under the presence of oxygen, where as pyrolysis is done under the absence (or near absence) of oxygen.
What is a Thermal Column (Heat Stratification)
Heat layers that occur in a room as a result of a fire.
The phenomenon of gases forming into layers according to temperature.
What is a Neutral Plane
The common boundary or interface between the hot gases and cooler gases.
It is the volume of space in a compartment opening at which the pressure of hot gases and smoke leaving the compartment and the pressure of the cooler air entering the compartment are equal.
In order for a neutral plane to exist, there must be a flow of cooler air entering the compartment and a flow of hot gases exiting the compartment.
What is a Rollover?
Also, what other name is it known as?
Is the spontaneous ignition of hot gases in the upper levels of a room or compartment. This is a sign that the temperature is rising and if it gets hotter the room and the contents will spontaneously and rapidly ignite.
Also known as a Flameover.
What is a Flashover
Not a specific moment, but rather a transition from a fire that is growing by igniting one type of fuel to another, to a fire where all of the exposed surfaces have ignited. It is a rapid change or transition from the growth stage to the fully developed stage.
Wind Effect greatly influences fire behavior. For example, when the wind is still, the best approach to a fire is through the A side of a building. Conversely, if the wind is blowing at 20 to 25 miles per hour from the C side, entering the A side may be a deadly miscalculation. Fig 5-25
What is a Boiling Point
What is the boiling point of water?
The temperature at which a liquid will continually give off vapors in sustained amounts and, held at the temperature long enough, will turn completely into a gas.
212 degrees Fahrenheit. As the boiling point is reached, the amount of flammable vapor generated increases significantly (Fig 5-26)
What is a Flash point:
What is a Fire point (Aka Flame Point):
The lowest temperature at which a liquid or solid produces a flammable vapor.
The lowest temperature at which a liquid produces enough vapor to sustain a continuous fire.
For most materials, the fire point is only slightly higher than the flash point.
CHARACTERISTICS OF GAS-FUEL FIRES:
What are the two terms used to describe the characteristics of flammable vapors?
Explain both:
- Vapor Density: Refers to the weight of a gas fuel and measures the weight of the gas compared to air (Table5-3)
- Flammable Range (Explosive Limit): The range in concentration between the lower and upper flammable limits.
BLEVE
Boiling Liquid/Expanding Vapor Explosion: Occurs when a liquid fuel is stored in a vessel under pressure.
The key to preventing a BLEVE is to cool the top of the tank, which contains the vapor, which prevents the fuel from building up enough pressure to cause a catastrophic rupture of the container.
There are two type of flow that smoke can have. What are they and its definition?
Laminar Smoke Flow: A smooth or streamlined flow, which indicates that the box and its contents are absorbing heat and the pressure in the box is not too high (Fig. 5-29).
Turbulent Smoke Flow: Is agitated, boiling, or angry. This expansion occurs when the box (building) cannot absorb any more heat. When you see turbulent smoke, be aware that flashover is likely to occur soon.
