Fire Behavior Flashcards
Matter
Anything that occupies space and has mass
Define fire
Heat producing chemical reaction between some type of fuel and oxygen that burns, heat is generated faster than it can be dissipated and increases in temperature.
Physical change
Occurs when a substance remains chemically the same but changes in size, shape, or appearance
Chemical reaction
Occurs when a substance changes from one type of matter into another
Oxidation
Is a chemical reaction involving the combination of oxygen
An example of oxidation is …..
Metal to rust
Our atmospheres a composed of what percent oxygen?
21%
Exothermic heat reaction
Chemical reaction between two or more materials that changes the materials and produces heat, flames , and toxic smoke
Endothermic heat reaction
Chemical reaction in which a substance absorbs heat energy
Combustion
An Exothermic chemical reaction that is a self sub staining process of rapid oxidation of a fuel that produces heat and light
Fire is an example
Flaming combustion
Oxidation involves fuel in the gas phase
Heat of both liquid and solid fuels will give off vapors that mix with oxygen and can burn producing flames
Non flaming or smoldering combustion
Under oxidation at the surface that char but no flame is present
Example charcoal
Fire triangle
Oxygen
Heat
Fuel
Fire tetrahedron
Oxygen
Heat
Fuel
Self sustained chemical chain reaction
Heat
Is a source of energy that exists in two states potential and kinetic
Potential energy
Stored energy possessed by an object that can be released in the future to perform work
Kinetic energy
The energy possessed by a moving object
Chemical energy is converted into kinetic energy in the form of heat and light.
Temperature
Is the measurement of kinetic energy
(BTU)
British thermal unit
Is the amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit
What are the two most common ways of measuring temperature?
Celsius- metric system
Fahrenheit - customary system
Pyrolysis
The chemical decomposition of a substance through the action if heat.
Solid to vapor form during the burning process
Vaporization
Liquid to vapor form
What are two types of Ignition
Piloted ignition
Auto ignition
Piloted ignition
Occurs when a mixture of a fuel and oxygen encounters an external heat source that starts combustion
Auto ignition
Occurs without any external flame or spark to ignite the fuel. Surface is chemically heated to the point in which combustion occurs
(AIT)
Auto ignition temperature
Is the temperature to which the surface of a substance must be heated for ignition and self sustained combustion to occur
What is the most common source of heat in combustion reactions
Chemical heat energy
What occurs when a spontaneous heating forms a chemical heat energy and increases temperature without addition of external heat
Self- heating
Electrical heat energy
Can generate temperatures high enough to ignite any combustible material near the heated area
What are 4 types of electrical heating
Resistance
Over current or overload
Arcing
Sparking
Resistance heating
Electric current flows through a conductor and heat is produced
Over current or overload
Current flows through a conductor exceeds it’s design overheating presenting ignition
Arching
An arc is a high temperature luminous electric discharge across a gap or through a medium
Sparking
Arc occurs producing particles that spatter away from the point of arching
Mechanical heat energy
Is generated by friction or compression
Heat of friction
The movement of two surfaces against each other creating heat or sparks
Heat of compression
Is generated when gas is compressed
Heat can be transferred in how many ways?
3
Conduction
Convention
Radiation
Conduction
Is the transfer of heat within a body or to another body by direct contact
The flow of energy between two solids
Convection
Transfer of heat by movement of heated fluids or gases
Hot air/ liquids rise as cold falls
Radiation
Transmission or transfer of energy of heat energy from one body to another at a lower temp through intervening space by electromagnetic waves
Such as the sun or a microwave
Thermal radiation
Results from temperature
Passive agents
Are materials that absorb heat but don’t participate actively in the combustion reaction
Fuel
Is the material or substance being oxidized or burned in the combustion process
The fuel in a combustion reaction is known as
A reducing agent
Organic fuels
Contain carbon
Cellulose based
Produces ash
Hydrocarbon based fuels
Gasoline, oils, plastics
Define the composition of Gaseous fuels
Have a mass but no Definite shake or volume
Vapor density
Describes the density of gases in relation to air. Air is assigned 1.0 gases with a vapor less than 1.0 will rise as those more than 1.0 will sink
Liquids are
A mass and volume with no definite shape
Specific gravity
Is the ratio of the mass of a given volume of liquid compared with the mass (weight) of an equal volume of water at the same temp
Water is assigned 1.0 lighter will float heavier will sink
Vaporization
Transformation of a liquid to vapor or gaseous state
Flash point
Is the temperature at which vapors ignite but not enough to sustain combustion
Fire point
Is the temp at which sufficient vapors are being generating to sustain combustion.
Solubility
Describes the extent to which a substance will mix with water
Miscible
Means it will mix with water in any proportion
Pyrolysis
Chemical decomposition of a substance through a action of heat
Solid when heated decomposes to a vapor state
What is the primary consideration surface area of the fuel proportion to the mass
Surface to mass ratio
The solid fuel relative to the source of heat affects the way it burns by
Proximity
Materials can support combustion until the oxygen concentration drops below what percent
14%
Fires in oxygen enriched atmospheres present what danger
Fires burn intensely and ignite or rapidly
Flammable range
The range between the upper flammable limit and lower I’m which a substance can ignite
Too lean
Not enough oxygen to cause combustion
Too rich
To much vapors
Flaming combustion
An example of a chemical chain reaction or fire
Self sustained chemical reactions
Rapid growth the separate flames and combustion is to slow causing oxidation such as rust
A fire is
energy in the form of heat and light
Carbon monoxide
Is a byproduct of the incomplete combustion of organic materials
Most common in structure fires
How many classifications of fires are there?
5 Alpha Bravo Charlie Delta Kilo
Alpha fires
Combustible materials that produce ash
Bravo fires
Combustible liquids
Charlie fires
Energized electrical fires
Delta fires
Combustible metals
Kilo fires
Oils and greases
Compartment
Is an enclosed room or space within a building.
How many steps to fire development
4 Incipient Growth Fully developed Decay
Inciting stage
Starts with ignition describes the point of the combustion process
What is the process of hot gasses and flames rising from the heat source and seeking colder air
Plume
When plumes start reaching across the ceiling horizontally is known as
Mushrooming
Growth stage
Increasing heat, fuel and oxygen virtually limitless
Begins to influence the environment within the compartment
Thermal layering
Tendency of gases to form layers avoids on to temperatures
Thermal balance
Hottest gasses tend to rise as the cold form the lower layer
Roll over
Condition where the Unburned fire gases accumulate at the top of the compartment ignite and propagate through the layers of gases
Flash over
Rapid transition between the growth and fully developed stages
Thermal layers are equal in temp throughout the compartment
Fully developed stage
All combustible materials in the compartment are burning producing large volumes of gas
Decay
Fuel is consumed or oxygen concentration falls below 14% making combustion no longer possible
Backdraft
Sudden increase in ventilation resulting in deflagration or rapid combustion
Common signs for possible backdraft include
Smoke leaving I'm puffs Little or no visible flames Drawn smoke or sucking Excessive heat in windows and stained Smoke exiting small openings Black or gray smoke to orange smoke variations
Factors that influence fore development include
Fuel type Additional fuels Compartment layout Ventilation Thermal properties Ambient conditions
