IFSTA Chapter 3 - Fire Behavior
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anything that occupies space and has mass
What is an exothermic heat reaction?
- chemical reaction between two or more materials that changes the material and produces heat, flames, and toxic smoke
- (heat is released)
What is an endothermic heat reaction?
chemical reaction in which a substance absorbs heat energy
What is potential energy?
- energy that is stored but not is use
- energy that may be released in the future
- an exothermic chemical reaction that is a self-sustaining process of rapid oxidation of fuel
- produces heat and light
What are the 3 parts of the fire triangle?
What are the 4 parts of the fire tetrahedron?
- self-sustaining chemical reaction
Define kinetic energy.
the energy possessed by a moving object
What are Btus?
- unit of measurement for heat
- the amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit
the chemical decomposition of a substance through the action of heat
What is piloted ignition?
occurs when a mixture of fuel and oxygen encounter an external heat course with sufficient heat energy to start the combustion reaction
What is autoignition?
- occurs without any external flame or spark to ignite the fuel or gases or vapors
- fuel surface is chemically heated to the point at which combustion occurs
True or false: The autoignition temperature of a substance is always higher that it's piloted ignition temperature.
Define autoignition temperature
the temp to which the surface of a substance must be heated for ignition and self-sustaining combustion to occur
True or False: Chemical heat energy is the most common source of heat in combustion reactions
a form of chemical heat energy that occurs when a material increases in temperature without the addition of external heat
What are the ways electrical heating can occur?
- resistance heating
- overcurrent or overload
Define mechanical heat energy.
heat energy generated by friction of compression
What is heat of friction?
heat created by the movement of two surfaces against each other
What are the ways heat can be transferred from one body to another?
physical flow or transfer of heat energy from one body to another through direct contact or an intervening medium from the point where heat is produced
the transfer of heat by the movement of heated fluids or gases, usually in an upward direction
the transmission of heat energy as an electromagnetic wave, such as light waves, radio waves, or x-rays, without an intervening medium
What are passive agents?
- materials that absorb heat but do not participate actively in the combustion reaction
- ex: fuel moisture - a well watered shrub will be slower to ignite than a dehydrated one
What are inorganic fuels?
- fuels that do not contain carbon
- ex: hydrogen, magnesium
What are organic fuels?
fuels containing carbon
What are examples of hydrocarbon fuels?
What are examples of cellulose-based materials?
What are gaseous fuels?
- fuels that are already in the sate required for ignition
- ex: methane, hydrogen, acetylene
Define vapor density.
the density of gases in relation to air
Define specific gravity.
the weight of a substance compared to the weight of an equal volume of water at a given temp
the process that charges a liquid into a gaseous state
Define flash point
minimum temperature at which a liquid gives off enough vapors to ignite, but not sustain combustion
Define fire point
the temperature at which sufficient vapors are being generated to sustain the combustion reaction
What is solubility?
the extent at which a substance will mix with water
What is miscible?
materials that are capable of being mixed
Define heat release rate.
- the energy released per unit of time as a given fuel burns
- usually expressed in kilowatts
What are common products of combustion?
- Carbon monoxide (CO)
- Hydrogen cyanide (HCH)
- Carbon dioxide (CO2)
What is a Class A fire?
- involve ordinary combustible materials such as wood, cloth, paper, rubber, grass, and many plastics
- water is most commonly used on Class A fires
What is a Class B fire?
- fires involving flammable and combustible liquids and gases such as gasoline, oil, lacquer, paint, mineral spirits, and alcohol
- extinguished by cutting off gas supply, applying appropriate foam or dry chemical agents
What are Class C fires?
- involve energized electrical equipment such as household appliances, computers, transformers, electric motors
- actual fuel burning is usually the insulation on wiring or lubricants
- always cut the power if possible
What are Class D fires?
- involve combustible metals such as aluminum, magnesium, potassium, sodium, titanium
- in the right concentrations, airborne metal dusts can cause powerful explosions when given an ignition
What are Class K fires?
involve oil and grease normally found in commercial kitchens
- a endothermic way to put out class k fires
- occurs when mixtures of alkaline-based chemicals and certain cooking oils come into contact and form a soapy film that absorbs heat
What are the stages of fire development (in order)?
- fully developed
Define the incipient stage.
- first stage of the burning process
- the substance being oxidized is producing some heat but has not spread to other substances nearby
Define the growth stage
- early stage of fire development during which fuel and O2 are virtually unlimited
- characterized by a rapid increase of heat
Define thermal layering.
the outcome of combustion in a confined space in which gases tend to form into layers, according to temp (hottest gases at the top/ceiling, coolest gases as the bottom/floor)
What is the neutral plane?
the interface of the hot and cooler gas layers (where they meet)
What is a rollover?
condition where the unburned fire gases accumulated at the top of a compartment ignite and flames propagate through the hot gas later or across the ceiling
What is a flashover?
stage of a fire at which all surfaces and objects within a space have been heated to their ignition temp and flame breaks out almost at once over the surface of all objects in the space
What is the fully developed stage?
stage of burning process where energy release in at maximum rate and is limited only by availability of fuel and O2
What is the decay stage?
- state of fire development when fuel is consumed, energy release diminishes, and temp decreases
- fire goes from ventilation controlled to fuel controlled
instantaneous explosion or rapid burning of superheated gases that occurs when O2 introduced into an O2-depleted confined space
What are the factors that affect fire development?
- fuel type
- availability and location of fuel in relation to the fire location
- compartment geometry (volume/ceiling height)
- ventilation and changes in ventilation
- thermal properties of the enclosure
- ambient conditions (wind, temp, humidity)
When water is converted into steam at 212 degrees F, it expands approximately ____ times.
What is the most common method of fire control and extinguishment?
cooling with water
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