Fire Dynamics (IFSTA) Flashcards
Describes the meeting point between fire science, materials science, fluid dynamics of gases, and heat transfer
Fire dynamics
Understanding ___ can give firefighters the knowledge needed to forecast fire growth at a scene and predict the likely consequences of various tactical options available for controlling the fire
The basic physics of fire dynamics
Firefighters should have a scientific understanding of ___
Combustion, fire, heat, and temperature
All fires involve a ___
Heat-producing chemical reaction between some type of fuel and an oxidizer
Most common oxidizer
Oxygen in the air
Not combustible, but will support or enhance combustion
Oxidizer
Calcium Hypochlorite, Chlorine, Ammonium Nitrate, Hydrogen Peroxide, and Methyl Ethyl Ketone Peroxide are all ___
Oxidizers
Calcium Hypochlorite common use
Chlorination of water in swimming pools
Chlorine common use
Water purification
Ammonium nitrate common use
Fertilizer
Hydrogen Peroxide common use
Industrial bleaching (pulp and paper and chemical manufacturing)
Methyl Ethyl Ketone Peroxide common use
Catalyst in plastics manufacturing
The study of matter and energy and includes chemistry and physics
Physical science
The theoretical foundation of physical science must be translated into ___
A practical knowledge of fire dynamics
To remain safe, you need to be able to ID the ___ present in a given situation and anticipate what the ___ will be along with how ___ may impact the fire’s behavior
- Fire dynamics
- Next stages of the fire
- Fire fighting operations
Occurs when a substance remains chemically the same, but changes in size, shape, or appearance
Physical change
Water freezing or boiling is a ___ change
Physical
Occurs when a substance changes from one type of matter into another, such as two or more substances combining to form compounds
Chemical reaction
Chemical reaction involving the combination of an oxidizer with other materials
Oxidation
Speed of oxidation
Can range from slow to ultra rapid
The capacity to perform work
Energy
Occurs when a force is applied to an object over a distance or when a substance undergoes a chemical, biological, or physical change
Work
In the case of heat, work means ___
Increasing a substance’s temperature
Forms of energy are classified as either ___
Potential or kinetic
Represents the amount of energy that an object can release at some point in the future
Potential energy
Fuels have a certain amount of potential energy before they are ignited, based on their ___
Chemical composition
The potential energy available for release in the combustion process is known as the ___
Heat of combustion
The rate at which a fuel releases energy over time depends on ___
- Chemical composition
- Arrangement
- Density of the fuel
- Availability of oxygen for combustion
The energy that a moving object possesses
Kinetic energy
When heat is introduced to a fuel such as wood, the molecules within the fuel begin to ___
Vibrate
As the thermal energy increases, the molecules within a fuel ___
Vibrate more and more rapidly
The fuel’s kinetic energy is the result of ___
These vibrations in the molecules
Types of energy
- Chemical
- Thermal
- Mechanical
- Electrical
- Light
- Nuclear
- Sound
All energy can change from ___
One type to another
In terms of fire behavior, the potential chemical energy of a fuel converts into ___ during combustion
Heat and light
Energy is measured in ___ in the International System of Units (SI)
Joules (J)
The quantity of heat required to change the temperature of 1 gram of water by 1°C
4.2 joules
In the customary system, the unit of measurement for heat is the ___
British Thermal Unit (Btu)
A Btu is the amount of heat required to raise the temperature of 1 lb of water by ___
1°F
1 Btu = ___ J
1055
Chemical and physical changes almost always involve an ___
Exchange of energy
A fuel’s potential energy releases during combustion and converts to ___
Kinetic energy
Reactions that emit energy as they occur
Exothermic reactions
Fire is an ___ chemical reaction that releases energy in the form of ___
- Exothermic
- Heat and sometimes light
Reactions what absorb energy as they occur
Endothermic reactions
Converting water to steam requires ___ resulting in an ___ reaction
- The input of energy
- Endothermic
Converting water to steam is a tactic for ___ some types of fires
Controlling and extinguishing
Models used to explain the elements of fire and how fires can be extinguished
Fire triangle and fire tetrahedron
___ is an example of gas-phase combustion
Fire
Fire triangle elements
- Oxygen
- Fuel
- Heat
Fire tetrahedron elements
- Oxygen
- Fuel
- Heat
- Uninhibited chemical chain reaction
The fire tetrahedron includes ___ to explain flaming or gas-phase combustion
The chemical chain reaction
Fuels must be in a ___ state to burn
Gaseous
Solids and liquids must become gaseous in order for ___ to occur
Ignition
Converting to a gaseous state
Off-gassing
In solids, off-gassing is a chemical change known as ___
Pyrolysis
In liquids, off-gassing is a physical change known as ___
Vaporization
When heat is transferred to a liquid or solid, the substance’s temperature increases and the substance starts to ___
Off-gas
Most common form of ignition
Piloted ignition
Occurs when a mixture of fuel and oxygen encounter an external heat source with sufficient heat or thermal energy to start the combustion reaction
Piloted ignition
Occurs without any external flame or spark to ignite the fuel gases or vapors
Autoignition
The fuel’s surface is heated to the point at which the combustion reaction occurs
Autoignition
Illustrates the components needed for a fire
Fire triangle
Illustrates the components needed for a self-sustained fire
Fire tetrahedron
Once the fuel is ignited, the energy released from combustion ___
Transfers to the remaining solid fuel resulting in the production and ignition of additional fuel vapors or gases
The exchange of energy from the burning gases to the fuel results in a ___
Sustained combustion reaction
The minimum temperature at which a fuel in the air must be heated in order to start self-sustained combustion
Autoignition temperature
AIT
Autoignition temperature
The autoignition temperature is always ___ than its piloted ignition temperature
Higher
Combustion is a ___ while flaming combustion is ___
- Chemical reaction
- Only one form of combustion
Combustion can occur without ___
Visible flames
Two modes of combustion
Flaming and nonflaming
Occurs more slowly and at a lower temperature, producing a smoldering glow in the material’s surface
Nonflaming combustion
The burning in nonflaming combustion may be localized ___
On or near the fuel’s surface where it is in contact with oxygen
Burning charcoal or smoldering wood or fabric are examples of ___
Nonflaming combustion
The ___ illustrates the elements/conditions required for nonflaming combustion
Fire triangle
Flaming combustion is commonly referred to as ___
Fire
Produces a visible flame above the material’s surface
Flaming combustion
Occurs when a gaseous fuel mixes with oxygen in the correct ratio and heats to ignition temperature
Flaming combustion
Flaming combustion requires liquid or solid fuels to be ___
Converted to the gas phase through the addition of heat
When heated, both liquid and solid fuels will emit ___ that ___, producing flames above the material’s surface if the gases ignite
- Vapors
- Mix with oxygen
Accurately reflects the conditions required for flaming combustion
Fire tetrahedron
Each element of the tetrahedron must be in the ___ for flaming combustion to occur
Proper proportion and in close physical proximity
Removing any element of the tetrahedron interrupts the ___
Chemical chain reaction
After flaming combustion stops, the fire may continue to ___
Smolder depending on the characteristics of the fuel
Where the combustion process begins
Ignition
A heat source ___ a fuel, creating ___, which ___, creating fire
- Pyrolizes
- Fuel gases
- Ignite
How can fire be compared to a pump?
Fresh oxygen is pumped in and mixes with fuel gases. It then pumps out combustion products
The combustion products pumped out by a fire have larger amounts of ___ and a higher level of ___ than the inlet air
- Mass
- Energy
In the case of open burning, the pump does not have a well-defined ___
Inlet or outlet
Drawn in
Entrained
As heat generated by the fire transfers to the gaseous combustion products, they ___
Expand and begin to rise and move away from the fire due to buoyancy
The density of the hot combustion products is ___ than the surrounding air
Less
As fuel burns, its chemical composition changes, which produces ___
New substances
Products of combustion are often simply described as ___
Heat and smoke
Cause most fire deaths
Exposure to toxic gases found in smoke and/or lack of oxygen
An aerosol comprised of gases, vapor, and solid particulates
Smoke
Smoke is the product of ___
Incomplete combustion
Examples of left over fuel from incomplete combustion
Smoke and ash
Under ideal conditions, the entire fuel would undergo a chemical conversion from ___
Its current form into an equal amount of new materials
Complete combustion of methane in air results in the production of ___
Heat, light, water vapor, and carbon dioxide
Combustion is ___ in a structure fire
Incomplete
what happens with incomplete combustion in a structure fire?
Some fuel does not burn, but instead gets entrained in hot gases and rises aloft
Smoke has the potential to ___
Burn
Most structure fires involve multiple types of ___, and tend to have a limited ___
- Fuels
- Air supply
Wood and cotton are ___ fuels
Carbon-based
Plastics and synthetic fabrics are ___ fuels
Hydrocarbon
When the air supply is limited, the level of ___ is higher, which produces more ___
- Incomplete combustion
- Smoke
___ give smoke its varied colors
Vapor and particulates
The materials that make up smoke vary from ___
Fuel to fuel
Generally all smoke is ___
Toxic
The toxic effects of smoke inhalation are the result of the ___
Interrelated effect of all the toxic products present
The combustion process consumes ___ from the air
Oxygen
The consumed oxygen combines with carbon in the smoke to form ___
Combustion products like CO or CO2
The toxic gases in combination with a low oxygen concentration can reduce the time that ___
A victim could survive
Concentrations of the products of combustion and/or low oxygen concentrations can cause ___
Asphyxiation
Fatal level of oxygen deficiency in the blood
Asphyxiation
Toxic and flammable product of the incomplete combustion of organic materials. It is colorless, odorless gas present at almost every fire
Carbon Monoxide
CO is released when ___
An organic material burns in an atmosphere with a limited supply of oxygen
Toxic effects of CO
- Headache
- Dizziness
- Weakness
- Confusion
- Nausea
- Unconsciousness
- Death
Exposure to as little as ___ CO can result in unconsciousness within ___
- 0.2%
- 30 min
Inhalation of a high concentration of CO can result in ___
Immediate collapse and unconsciousness
Formaldehyde is a ___
Colorless gas with a pungent, irritating odor that is highly irritating to the nose
Concentrations of formaldehyde that can cause severe irritation to the respiratory tract and serious injury
50-100 ppm
Formaldehyde exposure in high concentrations can cause ___
Injury to the skin
Formaldehyde is a suspected ___
Carcinogen
Hydrogen cyanide is ___
A colorless, toxic, and flammable liquid produced by the combustion of nitrogen bearing substances
Hydrogen cyanide is flammable below ___
79°F
Hydrogen cyanide is commonly encountered in ___
Smoke in concentrations lower than CO
How does hydrogen cyanide asphyxiate?
Chemical asphyxiant that prevents the body from using oxygen
Nitrogen dioxide is a ___
Reddish-brown gas or yellowish-brown liquid, which is highly toxic and corrosive
Small particles that can be inhaled and deposited in the mouth, trachea, or lungs
Particulates
Exposure to particulates can cause ___
Eye irritation and respiratory distress
Sulfur dioxide is ___
A colorless gas with a choking or suffocating odor, and is toxic and corrosive
Sulfur dioxide exposure can cause ___
Irritation of the eyes and mucous membranes
CO is a ___ asphyxiant
Chemical
CO attach to ___, decreasing the blood’s ability to ___
- Hemoglobin
- Carry oxygen
Co combines with hemoglobin about ___ more effectively than oxygen does
200 times
CO does not act on the ___, but excludes ___
- Body
- Oxygen from the blood
CO exposure leads to ___
Hypoxia of the brain and tissues
HCN
Hydrogen cyanide
Incomplete combustion of substances that contain nitrogen and carbon produce ___
HCN
Long-term exposure to CO can cause ___
Cardiovascular disease
Possible mental health problems
Materials that produce HCN
- Natural fibers such as wool, cotton, and silk
- Resins such as carbon fiber or fiberglass
- Synthetic polymers such as nylon or polyester
- Synthetic rubber such as neoprene, silicone and latex
Synthetic rubber such as neoprene, silicone, and latex is found in ___
- Upholstered furniture
- Bedding
- Insulation
- Carpets
- Clothing
- Other common building materials and household items
___ is a significant byproduct of the combustion of polyurethane foam
HCN
Polyurethane foam is used in many ___
Household furnishings
HCN is also released during ___ as an object is heated
Off-gassing
HCN may be found in vehicle fires, where new insulation materials ___
Give off high amounts of gases and cause fires to last longer
HCN is ___ more toxic than CO
35 times
HCN chemical asphyxiant method
Prevents the body from using oxygen at a cellular level
HCN routes into the body
Inhaled, ingested, or absorbed
HCN targets the ___
Heart and brain
Inhaled HCN enters the bloodstream and ___
Prevents the blood cells from using oxygen properly, killing the cells
The effect of HCN depend on the ___
Concentration, length, type of exposure
Large amounts, high concentrations, and lengthy exposures are more likely to cause ___
Severe effects, including permanent heart and brain damage or death
Wear ___ anytime you may be exposed to smoke, heat, or toxic gases
Full PPE and SCBA
Product of complete combustion of organic materials, it is not toxic like CO or HCN
CO2
CO2 acts as a respiratory ___
Stimulant
CO2 creates an oxygen deficient atmosphere by ___
Displacing existing oxygen
Exposure time is based on the ___
Combination of gases or the lethal effective dose
Substances that cause breathing discomfort and inflammation of the eyes, respiratory tract, and skin in smoke
Irritants
Smoke can contain a wide range of irritating substances, depending on the ___
Fuels involves
More than ___ irritants in smoke have been identified
20
Smoke contains significant amount of unburned fuels in the form of ___
Solid and liquid particulates and gases
Smoke must be treated with the same respect as any other flammable gas because it ___
May burn or explode
Particulates can interfere with ___
Vision and breathing
Force per unit area applied perpendicular to a surface
Pressure
Indicates the amount of pressure that the atmosphere applies to the surface of the earth
Atmospheric pressure
Low concentrations of HCN cause ___
- Eye irritation
- Headache
- Confusion
- Nausea
- Vomiting
- Coma (in some cases)
- Fatality (in some cases)
High concentrations of HCN cause ___
Immediate CNS, cardiovascular, and respiratory distress leading to death within minutes
At standard temperature and atmospheric pressure, gases remain ___
Calm
Differences in pressure above or below standard pressure create ___
Movements in gases
Gases always move from areas of __
Higher pressure to lower pressure
Pressure difference created in most compartment fires
0.1 kPa or less
Heat from a fire ___ the pressure of the surrounding gases
Increases
The increased pressure will seek to ___
Expand and equalize with areas of lower pressure
Heated gases will ___
Rise, remain aloft, and generally travel up and out
As heated gases rise, cooler, fresh air will ___
Generally travel inward toward the fire
Remain aloft
Buoyant
The exchange of cool air for hot air creates a ___
Convective flow
What increases the convective flow?
Larger pressure differences between high and low pressure areas
The thermal kinetic energy needed to release the potential chemical energy in a fuel
Heat
The fuel emits flammable vapors which can ignite and release thermal energy. This new source of thermal energy begins to heat other, uninvolved fuels ___
Converting their energy and spreading the fire
Measurement of heat
Temperature
The measurement of the average kinetic energy in the particles of a sample of matter
Temperature
A block of wood at room temperature has ___ molecules
Stable
Most common scales to measure temperature
- Celsius (SI)
- Fahrenheit (customary system)
Provide a way to compare the two temperature scales
Freezing and boiling points of water
A dangerous misconception is that temperature is an accurate predictor or measurement of ___
Heat transfer
One candle burns at ___ temp as 10 candles
The same
The heat release rate of 10 candles is ___ than one candle at the same temperature
10 times greater
The increased heat release rate results in an increased ___ to an object
Heat transfer rate
Energy flow to a unit area
Heat flux
Heat flux is measured in ___
Kilowatts per square meter
Translated to an interior fire environment, the temperature in the structure may be within tolerances for PPE, however, the ___ indicates the real measurement of how long the PPE will protect you
Heat flux to the PPE from the fire
The ___ tells you it is safe to go in, but the ___ tells you how long you can stay in
- Temperature
- Heat transfer rate
Common sources of heat that result in the ignition of a fuel
Chemical, electrical, and mechanical energy
Most common source of heat in combustion reactions
Chemical energy
The potential for oxidation exists when ___
Any combustible fuel is in contact with oxygen
The oxidation process almost always results in the production of ___
Thermal energy
A form of oxidation, is a chemical reaction that increases the temperature of a material without the addition of external heat
Self-heating
Self-heating can lead to ___
Spontaneous ignition
Ignition without the addition of external heat
Spontaneous ignition
Oxidation normally produces thermal energy ___
Slowly
Factors required for self-heating to progress to spontaneous ignition
- Insulation properties of the material immediately surrounding the fuel must be such that the heat cannot dissipate as fast as it is generated
- Rate of heat production must be great enough to raise the temperature of the material to its autoignition temperature
- Available air supply in and around the heated material must be adequate to support combustion
Rags soaked in linseed oil, rolled into a ball, and thrown into a corner have the potential for ___
Spontaneous ignition
The natural oxidation of oil and the cloth will generate heat if some method of heat transfer such as air movement around the rags does not ___
Dissipate the heat
The rate of most chemical reactions ___ as the temperature of the reacting materials increases
Increases
The oxidation reaction that causes heat generation accelerates the the fuel ___
Generates and absorbs more heat
When the heat generated exceeds the heat being lost, the material may ___
Reach its autoignition temp and ignite spontaneously
Common materials prone to self-heating
- Charcoal
- Linseed oil soaked rags
- Hay and manure
Convert Celsius to Fahrenheit
(Fahrenheit - 32) / 1.8
Convert Fahrenheit to Celsius
(Celsius x 1.8) + 32
Electrical energy can generate temperatures high enough to ___
Ignite any combustible materials near the heated areas
Electrical heating can occur in several ways, including ___
- Resistance heating
- Overcurrent or overload
- Arcing
- Sparking
Electric current flowing through a conductor produces heat
Resistance heating
When the current flowing through a conductor exceeds its design limits, the conductor may overheat and present an ignition hazard
Overcurrent or overload
Overcurrent or overload is ___
Unintended resistance heating
A high-temperature luminous electric discharge across a gap or through a medium such as charred insulation
Arc
May be generated when there is a gap in a conductor such as a cut or frayed wire or when there is high voltage, static electricity, or lightning
Arcs
When an electrical arc occurs, luminous particles can form and splatter away from the point of arcing
Sparking
Friction and compression generate ___ energy
Mechanical
___ is generated when a gas is compressed
Heat
When a compressed gas expands, the gas ___
Absorbs heat
The transfer of heat from one point to another is part of the study of ___
Thermodynamics
Heat transfer from the initial fuel package to other fuels in and beyond the area of fire origin affects the ___ and is part of the ___
- Growth of any fire
- Study of fire dynamics
Heat transfers from warmer objects to cooler objects because heated materials will ___
Naturally return to a state of thermal equilibrium
All areas of an object are a uniform temperature
Thermal equilibrium
Objects at the same temperature to not transfer ___
Heat
The rate at which heat transfers is related to the ___
Temperature differential of the bodies and the thermal conductivity of the materials involved
The greater the temperature differences between the bodies, the greater the ___
Transfer rate
A material with higher thermal conductivity will transfer heat ___ than other materials
More quickly
Heat transfers from one body to another by three mechanisms ___
- Conduction
- Convection
- Radiation
The transfer of heat through and between solids
Conduction
___ occurs when a material is heated as a result of direct contact with a heat source
Conduction
___ results from increased molecular motion and collisions between a substance’s molecules, resulting in the transfer of energy through the substance
Conduction
The more closely packed the molecules of a substance are, the readily it will ___
Conduct heat
Heat transfer due to conduction is dependent on three factors ___
- Area being heated
- Temperature difference between the heat source and the material being heated
- Thermal conductivity of the heated material
___ is the least able to conduct heat of most substances
Air
Slow the conduction of heat from one solid to another
Insulating materials
Good insulators are materials that do not conduct heat well because ___
Their physical makeup disrupts the point-to-point transfer of heat or thermal energy
The best commercial insulators used in building construction are those made of ___
Fine particles or fibers with void spaces between them filled with a gas such as air
Gases do not conduct heat very well because ___
Their molecules are relatively far apart
The transfer of thermal energy by the circulation or movement of a fluid (liquid or gas)
Convection
In the fire environment, convection usually involves transfer of heat through the movement of ___
Hot smoke and fire gases
Heat flows from the hot fire gases to the ___
Cooler structural surfaces, building contents, and air
Direction of convection
Any
Vertical movement of convection is due to the ___
Buoyancy of smoke and fire gases
Lateral movement of convection is usually the result of ___
Pressure differences
Heat transfer due to convection is dependent upon three factors ___
- Area being heated
- Temperature difference between the hot fluid or gas and the material being heated
- Turbulence and velocity of moving gases
The transmission of energy as electromagnetic waves, such as light waves, radio waves, or X-rays, without an intervening medium
Radiation
Radiant heat can become the dominant mode of heat transfer as the fire ___
Grows in size
___ heat can have a significant effect on the ignition of objects located some distance from the fire
Radiant
Radiant heat transfer is a significant factor in fire development and spread in ___
Compartments
Factors that influence radiant heat transfer
- Nature of the exposed surfaces
- Distance between the heat source and the exposed surfaces
- Temperature of the heat source
Dark-colored materials emit and absorb heat ___ than light-colored materials
More effectively
Smooth or highly polished surfaces reflect ___ radiant heat than rough surfaces
More
Increasing distance ___ the effect of radiant heat
Reduces
Unlike other methods of heat transfer that depend on the temperature of both the heat source and exposed surface, radiant heat transfer primarily depends on the ___
Temperature of the heat source
As the temperature and heat release rate of the heat source increases, the radiant energy ___
Also increases
As an electromagnetic wave, radiated heat energy travels ___
In a straight line at the speed of light
Radiation is a common cause of ___ fires
Exposure
As the fire grows, it radiates more energy which other objects absorb as heat. It is possible that these objects also catch on fire
Exposure fire
Materials that ___ will disrupt the heat transmission from radiated heat
Reflect, absorb, or scatter radiated energy
Heat flux from radiated heat from flames or hot surfaces such as the walls and ceiling may cause PPE failure even then the ___
Temperature of the gases within a compartment are within acceptable limits
SCBA ___ especially are susceptible to radiated heat flux
Facecpieces
PPE is designed to insulate the wearer from a ___
Specific amount of heat long enough to extinguish the fire or exit the compartment under a limited set of conditions
PPE will not protect you ___
Indefinitely
Relying upon ___ is essential for monitoring PPE’s performance during operations
Personal, situational awareness “in the moment”
The methods of heat transfer rarely occur ___ during a fire
Individually
The fire radiates heat, causes ___ through hot fuel gases, and conducts heat through ___
- Convection
- Burning materials or metals that are involved in the fire
Convected heat and radiated heat that reaches walls and ceilings heats those surfaces which, in turn, begin to ___ to whatever extent possible based upon the material’s ___
- Conduct heat
- Thermal conductivity
Wherever the gear is compressed against skin or under clothing, heat will be ___
Conducted faster
Where the PPE is not in contact, it will radiate heat to the ___
Insulating air layer between your body and the interior surface of the gear
The transferred heat in PPE can cause ___
Heat stress and will eventually cause PPE to fail
The heat build-up in PPE is the direct result of ___
All the heat transfer methods acting at the same time
Normal body temp
98.6°F
Temp at which human skin begins to feel pain
111°F
Temp at which human skin receives a 1st degree burn injury
118°F
Temp at which human skin receives a 2nd degree burn injury
131°F
Temperature at which a phase where burned human tissue becomes numb
140°F
Temperature at which human skin is instantly destroyed
162°F
Temperature at which water boils and produces steam
212°F
Glass transition temperature of polycarbonate
284°F
Melting temperature of polycarbonate
446°F
Temperature at which charring of natural cotton begins
482°F
Temperature at which charring of modern protective clothing fabrics begins
> 572°F
Temperatures inside a post-flashover room fire
> 1112°F
The oxidized or burned material or substance in the combustion process
Fuel
Fuel may be found in any of the ___
States of physical matter
The fuel in the combustion reaction is known as the ___
Reducing agent
Fuels may be ___
Inorganic or organic
Inorganic fuels do not contain ___
Carbon
Most common fuels are ___
Organic
Hydrogen and magnesium are ___ fuels
Inorganic
Organic fuels can be divided into ___
Hydrocarbon-based fuels
A fuel’s chemical content influences both its ___
Heat of combustion and heat release rate
Total amount of thermal energy released when a specific amount of that fuel burns
Fuel’s heat of combustion
Different materials release more or less heat than others based on ___
Their chemical makeup
Synthetic materials are synthesized from ___
Petroleum products
The rate at which energy transfers
Power
The rate at which energy converts from one form to another
Power
The SI unit for power
Watt (W)
One watt is ___
1 joule per second (J/s)
In terms of fir behavior, power is the ___
Heat release rate during combustion
When a fuel is heated, ___ is being performed
Work
The speed with which this work occurs, heat release rate, is the amount of ___
Generated power
The energy released per unit of time as a fuel burns
Heat release rate
Heat release rate is usually expressed in ___
Kilowatts (kW) or megawatts (MW)
Heat release rate depends on the ___ of the fuel
Type, quantity, and orientation
Heat release rate directly relates to oxygen consumption because the ___
Combustion process requires a continuous supply of oxygen to continue
Typically, the more oxygen is available, the ___ the heat release rate
Higher
For flaming combustion to occur, fuels must be in the ___ state
Gaseous
___ energy is required to change solids and liquids into the gaseous state
Thermal
The common term used to describe the gaseous state of a fuel that would normally exist as a liquid or a solid at standard temperature and pressure
Vapor
Gaseous fuels such as methane, hydrogen, and acetylene, can be the most dangerous of all fuel types because they are ___
Already in the physical state required for ignition
When wood burns ___, the combustion products may contain methane, acetylene, and other fuel gases
Inefficiently
Methane vapor density
0.55
Propane vapor density
1.52
Carbon monoxide vapor density
0.96
Methane ignition temperature
1004°F
Propane ignition temperature
842°F
Carbon monoxide ignition temperature
1128°F
Describes the density of gases in relation to air
Vapor density
Vapor density of air
1.0
Gases with a vapor density less than 1 will ___
Rise
Gases with a vapor density greater than 1 will ___
Sink
Vapor densities are based upon the assumption that the density is measured at ___
Standard temperature and pressure
Heated gases expand and become ___
Less dense
Cooled gases contract and become ___
More dense
Have mass and volume but no definite shape except for a flat surface or the shape of their container, will not expand to fill all of the container
Liquid
Will expand to fill all of a container
Gas
The ratio of the mass of a given volume of a liquid compared to the mass of an equal volume of water at the same temperature
Specific gravity
Specific gravity of water
1.0
Liquids with a specific gravity less than 1 are ___
Lighter than water and will float on top
Liquids with a specific gravity greater than 1 are ___
Heavier than water and will sink
To burn, liquids must ___
Vaporize
The transformation of a liquid to vapor or gaseous state
Vaporization
Unlike solids, liquids retain their state of matter partly due to ___
Standard atmospheric pressure
For vaporization to occur, the escaping vapors must be at ___
A greater pressure than atmospheric pressure
The pressure that vapors escaping from a liquid exert
Vapor pressure
Vapor pressure indicates how easily a substance will ___
Evaporate into air
Flammable liquids with a ___ vapor pressure present a special hazard to fire fighters
High
The vapor pressure of the substance and the amount of thermal energy applied to it determines the rate of ___
Vaporization
The volatility or ease with which a liquid gives off vapor influences how easily it can ___
Ignite
The size of the liquid’s surface area also influences the extent to which the liquid will give off ___
Vapor
Minimum temperature at which a liquid gives off sufficient vapors to ignite, but not sustain combustion, in the presence of a piloted ignition source
Flash point
The temperature at which a piloted ignition of sufficient vapors will begin a sustained combustion reaction
Fire point
___ is commonly used to indicate the flammability hazard of liquid fuels
Flash point
Liquid fuels that vaporize sufficiently to burn at temperatures under ___ present a significant flammability hazard
100°F
Describes the extent to which a substance will mix with water
Solubility
Solubility may be expressed in ___
Qualitative terms (slightly or completely) or as a percentage (X% soluble)
Materials that are ___ in water will mix in any proportion
Miscible
Flammable liquids called ___ such as alcohols will mix readily with water
Polar solvents
Some liquids are lighter than water and do not ___, such as hydrocarbon fuels
Mix with it
Liquids that are ___ dense than water are more difficult to extinguish using water as the sole extinguishing agent
Less
Because liquid fuel is less dense and will not mix with water, adding water to the liquid fuel may ___
Disperse the burning liquid instead of extinguishing it, potentially spreading the fire to other areas
Firefighters should use ___ to extinguish liquid fuels that are not water soluble
The appropriate foam or chemical agent
Water soluble liquids will mix with some water based extinguishing agents, such as many types of fire fighting foam. The extinguishing agent will mix with the burning liquid and become ___
Much less effective at extinguishing the fire
Firefighters should use ___ for polar solvents
Alcohol-resistant fire fighting foams specifically designed
Have definite size and shape
Solid
When solid fuels are heated, they begin to ___
Pyrolize and release fuel gases and vapors
If there is enough fuel and heat, the process of pyrolysis generates sufficient ___
Flammable vapors to ignite in the presence of sufficient oxygen or another oxidizer
Gasoline fire point
-40°F to -35°F
Gasoline flash point
-45°F
The flashpoint of a liquid indicates the temperature at which the liquid will ignite ___
Temporarily
The fire point of a liquid indicates the temperature at which the liquid will ___
Continue to burn once ignited
When wood first heats, it begins to pyrolize and decompose into its ___
Volatile components and carbon
Wood vapors are usually ___ in color
White
Pyrolysis of wood begins at temperatures below ___
400°F
One of the most common materials in upholstered furniture
Flexible polyurethane foam
Solid fuels have a definite shape and size which significantly affects how easily they ___
Ignite
The primary consideration in how easily a solid fuel will ignite is the ___
Surface area of the fuel in proportion to its mass
Surface of the fuel in proportion to its mass
Surface-to-mass ratio
As the surface-to-mass ratio increases, the fuel particles become more ___
Finely divided
As fuel particles become more finely divided, the particles ability to ignite ___
Increases tremendously
As the surface area increases, more of the material is exposed to heat and generates ___ more quickly
Combustible pyrolysis
The proximity and orientation of a solid fuel relative to the source of heat affects the way the fuel ___
Burns
If you ignite one corner of a sheet of plywood lying horizontally, the fire will consume the fuel at a relatively ___ rate
Slow
If you ignite one corner of a sheet of plywood standing vertical, it burns much more ___, because ___
- Rapidly
- The heated vapors rise over more surface area and transfer more heat to the paneling
Primary oxidizing agent in most fires
Oxygen
Normal air oxygen concentration
About 21%
The energy release in fire is directly proportional to the amount of ___ available for combustion
Oxygen
When a fire ignites in an open area where air is plentiful, the fire will release energy based on the ___
Given surface area
When a fire ignites within a compartment with limited air supply, the fire can only react with oxygen from ___
The compartment’s air and any additional oxygen supplied through openings
In most compartment fires, the energy release is proportional to ___, not ___
- The limited amount of oxygen available
- The amount of fuel available to burn
Normal ambient temperature
68°F
At normal ambient temperatures, materials can ignite and burn at oxygen concentrations as low as ___
15%
When oxygen concentration is limited, the flaming combustion will ___, causing ___
- Diminish
- Combustion to continue in the nonflaming mode
Nonflaming or smoldering combustion can continue at extremely low ___ even when the surrounding environment’s temperature is ___
- Oxygen concentrations
- Relatively low
At high ambient temperatures, flaming combustion may continue at considerably lower ___
Oxygen concentrations
Specific gravity of gasoline
0.72
Specific gravity of diesel
<1.00
Specific gravity of ethanol
0.78
Specific gravity of methanol
0.79
Flash point of diesel
125°F
Flash point of ethanol
55°F
Flash point of methanol
52°F
Autoignition temperature of gasoline
853°F
Autoignition temperature of diesel
410°F
Autoignition temperature of ethanol
689°F
Autoignition temperature of methanol
867°F
Stage and temp of wood burning when moisture is released as the wood begins to dry; combustible and noncombustible materials are released to the atmosphere although there is insufficient heat to ignite them
- Stage 1
- Less than 392°
Stage and temp of wood burning when the majority of the moisture has been released; charring has begin; the primary compound being released in CO; ignition has yet to occur
- Stage 2
- 392°F to 536°F
Stage and temp of wood burning when rapid pyrolysis takes place; combustible compounds are released and ignition can occur; charcoal is formed by the burning process
- Stage 3
- 536°F to 932°F
Stage and temp of wood burning when free burning exists as the wood material is converted to flammable gases
- Stage 4
- Greater than 932°F
PUF
Polyurethane foam
Stage and temp of PUF burning when it pyrolyzes and transforms into combustible gases and liquid
- Stage 1
- Less than 392°F
Stage and temp of PUF burning as the liquid polyols continue to be heated, they will vaporize into combustible gases, as well. Ignition of these gases may occur at this stage
- Stage 2
- 392°F to 536°F
Stage and temp of PUF burning when pyrolysis continues at an increased rate. No char layer is formed
- Stage 3
- 536°F to 932°F
Ignition of PUF occurs at ___
698°F
Auto-ignition of PUF can occur at temps of ___
797°F to 833°F
As the surface-to-mass ration of a fuel becomes higher, the energy required for ignition is ___
Lower
Oxygen deficient atmosphere
Less than 19.5%
Even if oxygen levels are not low enough to trigger an alarm, reduced levels of oxygen potentially represent a significant hazard in the form of ___
Toxic contaminants
Oxygen enriched atmosphere
Above 23.5%
Risk of oxygen enriched atmosphere
Increased fire risk
Materials that burn at normal oxygen levels will burn more ___ and may ignite ___ in oxygen enriched atmospheres
- Intensely
- More readily
Some petroleum-based materials will ___ in oxygen enriched atmospheres
Autoignite
Many materials that do not burn at normal oxygen levels will ___ in oxygen enriched atmospheres
Burn
Nomex will burn in an atmosphere that is ___
About 31% oxygen
The range of concentrations of the fuel vapor and air that will support combustion
Flammable (explosive) range
The fuel’s flammable range is reported using the ___
Percent by volume of gas or vapor in air for the lower explosive limit and upper explosive limit
LEL
Lower explosive limit
UEL
Upper explosive limit
The minimum concentration of fuel vapor and air that supports combustion
LEL
Concentrations below the LEL are said to be ___
Too lean to burn
The concentration of fuel vapor and air that above which combustion cannot take place
UEL
Concentrations above the UEL are said to be ___
Too rich to burn
Within the flammable range, there is an ideal concentration at which there is ___
Exactly the correct amount of fuel and oxygen required for combustion
Variations in ___ can cause the flammable range to vary considerably
Temperature and pressure
As flaming combustion occurs, the molecules of a fuel gas and oxygen break apart to form ___
Free radicals
Electrically charged, highly reactive parts of molecules
Free radicals
Free radicals combine with oxygen or with the elements released from the fuel gas to form ___
New substances and even more free radicals
The process of creating free radicals which create more free radicals increases the speed of the ___
Oxidation reaction
The complete oxidation of methane releases ___
The elements needed to create CO2 and water as well as release energy in the form of heat and light
The breakdown of methane releases ___
Carbon and hydrogen which recombine with oxygen in the air to form CO
Occurs when an extinguishing agent interferes with the chemical reaction, forms a stable product, and terminates the combustion reaction
Chemical flame inhibition
Compartment fire development depends upon whether the fire is ___
Fuel-limited or ventilation-limited
When sufficient oxygen is available for flaming combustion, the fire is said to be ___
Fuel-limited
Under fuel-limited conditions, the ___ control fire development
Fuel’s characteristics such as heat release rate and configuration
Have access to all of the fuel needed to maintain combustion, however the fire does not have access to enough oxygen to continue to burn or to spread to all available fuel
Ventilation-limited
All compartment begin in the incipient stage as ___
Fuel-limited fires
Once the fire reaches the growth stage, the fire will either ___
Remain fuel-limited or the fire will become ventilation-limited
A fuel-limited fire will usually progress through the stages of fire development ___
In order
Ventilation-limited fires tend to enter an early ___ at the end of the growth stage because ___
- State of decay
- There is no longer enough available oxygen for the fire to become fully developed
Stages of fire development
- Incipient stage
- Growth stage
- Fully developed stage
- Decay stage
Three key factors that control how the fire develops
- Fuel properties
- Ventilation available
- Heat conservation
Starts with ignition when the three elements of the fire triangle come together and the combustion process begins
Incipient stage
At the incipient stage the fire is ___
Small and confined to a small portion of the fuel first ignited
The stage when more of the initial fuel package becomes involved and the production of heat and smoke increases
Growth stage
The stage where other fuels close to the initial fuel package may begin to pyrolize from radiant heat and could spread the fire to new fuel packages
Growth stage
Fire in the growth stage may ___ or may ___
- Continue to grow to become fully developed
- Enter an early state of decay depending upon available oxygen
Occurs when all combustible materials in the compartment are burning at their peak heat release rate based upon available oxygen
Fully developed stage
Oxygen consumed in the fully developed stage
Maximum amount that it can
If the fire is limited to one fuel package, the fully developed stage occurs when ___
The entire fuel package is on fire and the fire has reached its peak heat release rate
As the fire consumes the available fuel or oxygen and the heat release rate begins to decline, the fire enters the ___
Decay stage
If oxygen becomes available during the decay stage before complete extinguishment, these fires are likely to ___
Reenter the growth stage and rapidly become fully developed
Provides the most basic fire growth curve
Open burning
Open burning is also called ___
Free burn
Open burning is representative of a ___ fire
Fuel-limited
Open burning fire is considered fuel controlled because ___
A single item burning either outside or in a large, well-ventilated space means there is sufficient oxygen available to burn the fuel until it can no longer sustain combustion
As heat and fire gases are produced in open burning, they ___
Move away from the fuel and disperse throughout the environment remote from the burning fuel
The only limit or control on the heat release rate of a fire burning out in the open is ___
The fuel itself
The flow of fire gases as they rise and encounter the ceiling and then spread horizontally
Ceiling jet
Development in the incipient stage depends largely upon the ___
Characteristics and configuration of the fuel involved
In the incipient stage, the fire has not yet influenced the ___ within the compartment to a significant extent
Environment
During the ___ stage, occupants can safely escape from the compartment, and a portable extinguisher or small hoseline can safely extinguish the fire
Incipient
The transition from incipient to growth stage can occur ___
Quickly
A visual indicator that a fire is leaving the incipient stage is ___
Flame height
When flames reach ___ high, radiated heat begins to transfer more heat than convection
2.5’
When the flames transfer more heat via radiation than convection, the fire will then enter the ___ stage
Growth
If the fire enters ventilation-limited decay, it does not necessarily indicate that the fire is ___
In its final stage of development
The stage where the fire begins to influence more of the compartment’s environment and has grown large enough for the compartment configuration and amount of ventilation to influence it
Growth stage
Unconfined fires draw air from ___
All sides
Drawing in
Entrainment
The entrainment of air ___ the plume of hot gases, ___ flame length and vertical extension
- Cools
- Reducing
In a compartment fire, the location of the fuel package in relation to the ___ affects the amount of air that is entrained, and thus the amount of ___ that takes place
- Compartment walls
- Cooling
Fires in fuel packages in the middle of the room can entrain air from ___
All sides
Fires in fuel packages near walls can only entrain air from ___
Three sides
Fires in fuel packages in corners can only entrain air from ___
Two sides
The area where sufficient air is available to feed the fire
Combustion zone
When the fuel package is not in the middle of the room, the combustion zone ___
Expands vertically and a higher plume results
A higher plume increases the temperatures in the ___ and increases the ___
- Developing hot gas layer at ceiling level
- Speed of fire development
Heated surfaces around the fire radiate heat back toward the burning fuel which ___
Further increases the speed of fire development
A fire is said to be in the growth stage until the ___
Fire’s heat release rate has reached its peak
Two common routes to full development
- Fires that consume all available oxygen and transition to a state of ventilation-limited decay
- Fires that have enough oxygen and move through the growth phase and possibly into rapid fire development
Once the ceiling jet reaches the walls of the fire compartment, the ___ begins to develop
Hot gas layer
The tendency of gases to form into layers according to temperature, gas density, and pressure
Thermal layering
Provided there is no mechanical mixing from a fan or a hose stream, the hottest gases will form the ___, while the cooler gases will form the ___
- Highest layer
- Lower layers
In addition to the effects of heat transfer through radiation and convection, radiation from the hot gas layer also acts to ___
Heat the interior surfaces of the compartment and its contents
Changes in ___ and ___ can significantly alter thermal layering
- Ventilation
- Flow path
The space between the air intake and the exhaust outlet
Flow path
Multiple opening in a compartment create multiple ___
Flow paths
As the fire grows, the hot gas layer within the fire compartment gains ___
Mass and energy
As the mass and energy of the hot gas layer increases, so does the ___
Pressure
Higher pressure causes the hot gas layer to ___
Spread downwards within the compartment and laterally through any openings such as doors or windows
If the hot gas layer has no openings for lateral movement it will ___
Begin to fill the compartment starting at the ceiling and filling down
Isolated or intermittent flames may ___ hot gas layer
Move through the
Combustion of the hot gases in the hot gas layer indicates that ___
Portions of the hot gas layer are within their flammable range, and that there is sufficient heat to cause ignition
As the hot gases circulate to the outer edges of the plume or the lower edges of the hot gas layer, they find sufficient ___ to ignite
Oxygen
The phenomenon of isolated or intermittent flames moving through the hot gas layer frequently occurs before ___
More substantial involvement of flammable products of combustion in the hot gas layer
The appearance of isolated flames is sometimes an immediate indicator of ___
Flashover
The interface between the hot gas layers and cooler layer of air
Neutral plane
The neutral plane is named because the ___
Net pressure is zero, or neutral, where the layers meet
The neutral plane exists at ___
Openings where hot gases exit and cooler air enters the compartment
Most residential fires that develop beyond the incipient stage become ___-limited
Ventilation
While closed compartment reduces the heat release rate, fuel may continue to ___, creating ___
- Pyrolize
- Fuel-rich smoke
As the interface height of the hot gas layer descends towards the floor, the greater volume of smoke begins to interrupt the ___
Entrainment of fresh air and oxygen to the seat of the fire and into the plume
As the efficiency of combustion decreases, the heat release rate ___ and the amount of unburned fuel within the hot gas layer ___
- Decreases
- Increases
The interruption of fresh air being entrained into the fire by a lowering hot gas layer causes the fire within the compartment to ___
Burn less efficiently
With a ventilation-limited decay stage fire, the compartment fills with fuel-rich gases that only need ___ to ignite because of the ___
- More oxygen
- Higher temperatures in the compartment
Even if ___ decrease, pyrolysis can continue
Temperatures
If no other source of oxygen exists, the compartment will fill with black smoke and ___ the fuel gases
Slowly cool
The characteristics of the fuel and fuel load in today’s typical fires will cause fires to quickly become ___
Ventilation-limited
In order for a ventilation-limited fire to grow, it needs a ___
New supply of oxygen
If windows or doors fail, the sudden introduction of fresh air into a ventilation-limited fore creates a ___
Rapid increase in the heat release rate and the growth of the fire
The pressure outside the compartment is ___ than the pressure inside the compartment
Lower
Creating an opening provides a ___ along which the hot gases can now move from the high pressure area inside to the low pressure area outside
Flow path
Refers to the rapid transition from the growth stage or early decay stage to a ventilation-limited, fully developed stage
Rapid fire development
Events of rapid fire development
- Flashover
- Backdraft
Smoke explosions are also incidents of rapid fire development, but they involve ___
More than just one compartment of a structure
Rapid transition from the growth stage to the fully developed stage
Flashover
When flashover occurs, the combustible materials and fuel gases in the compartment ignite ___
Almost simultaneously
The result of flashover is ___
A full-room fire involvment
Flashover typically occurs during the fire’s ___ stage, but may occur during the ___ stage as the result of ___
- Growth
- Fully-developed
- A change in ventilation
During flashover, the environment in the room changes from ___ to a ___
- A two-layer condition (hot on top, cooler on bottom)
- Single, well mixed hot gas condition from floor to ceiling
As flashover occurs, the gas temperatures in the room reach ___
1100°F or higher
A significant indicator of flashover is ___
Rollover
A condition where the unburned fire gases that have accumulated at the top of a compartment ignite and flames propagate through the hot gas layer or across the ceiling
Rollover
Rollover may occur during the growth stage as the hot gas layer ___
Forms at the ceiling
Flames may appear in the hot gas layer when the combustible gases reach their ___
Ignition temperature
While the rollover flames add to the ___, this condition is not ___
- Total heat generated in the compartment
- Flashover
Rollover will generally precede flashover, but ___
It does not always result in flashover
Rollover contributes to flashover because ___
The burning gases at the upper levels of the room generate tremendous amounts of radiant heat which transfers to other fuels in the room. Those new fuels begin pyrolysis and release the additional gases necessary for flashover
The transition period between preflashover fire conditions to postflashover can occur ___
Rapidly
When the upper layer ignites during flashover, the amount of radiation increases to levels which rapidly ignite contents in the room, even if they are ___
Remote from the fire
During flashover the volume of burning gases can ___
Increase from about 1/4 or 1/2 of the room’s upper volume to fill the room’s entire volume and extend out of any openings
When flashover occurs, burning gases push out of compartment openings at a ___
Substantial velocity
Four common elements of a flashover
- Transition in fire development
- Rapidity
- Compartment
- Pyrolysis of all exposed fuel surfaces
Flashover represents a transition from the growth stage to the ___
Fully-developed stage
Flashover happens ___
Rapidly
For flashover to happen, there must be a ___ space
Enclosed
Two interrelated factors that determine whether a fire within a compartment will progress to flashover
- Must be sufficient fuel and the the heat release rate must be sufficient
- Ventilation
At the floor level, a heat flux of ___ is typical of rollover conditions at the start of the flashover
20 kW/m^2
Once flames begin to affect a surface, the heat flux can range from ___
60 to 200 kW/m^2
SCBA facepieces begin to fail after ___
5 minutes of exposure to a heat flux of 15 kW/m^2
Building indicators of flashover conditions
Interior configuration, fuel load, thermal properties, and ventilation
Smoke indicators of flashover conditions
Rapidly increasing volume, turbulence, darkening color, optical density, and lowering of the hot gas layer/neutral plane
Heat indicators of flashover conditions
Rapidly increasing temp in the compartment, pyrolysis of contents or fuel packages located some distance away from the fire, or hot surfaces
Flame indicators of flashover conditions
Isolated flames or rollover in the hot gas layers near the ceiling
Levels of the ___ observed from the exterior of the structure are good indicators of fire behavior within the structure
Neutral plane
High neutral plane may indicate that ___
The fire is in the early stages of development or a fire above your level
High ceilings can hide a fire that has reached ___
A later development stage
Mid-level neutral plane could indicate that ___
The compartment has not yet ventilated or that flashover is approaching
Very low-level neutral plane may indicate that ___
The fire is reaching backdraft conditions or a fire is below you
When a fire is in ventilation-limited decay, the introduction of new oxygen can trigger ___ quickly
Flashover
In an uncontrolled situation, it may be difficult to ID what stage a fire is in, so firefighters should assume that flashover may occur at any time that the ___
Conditions are right
In increase in ventilation such as opening a door to a ventilation-limited compartment can result in an explosively rapid combustion of the flammable gases
Backdraft
Backdraft occurs in a space containing a ___
High concentration of heated flammable gases that lack sufficient oxygen for flaming combustion
When potential backdraft conditions exist in a compartment, the introduction of a new source of oxygen will ___
Return the fire to a fully involved state rapidly (often explosively)
Backdraft can occur with the creation of a ___ opening
Horizontal or vertical
Backdraft conditions can develop within a ___
Room, void space, or an entire building
Anytime a compartment or space contains hot combustion products, firefighters must consider potential for backdraft before creating any ___
Openings into the compartment
Building indicators of backdraft
Interior configuration, fuel load, thermal properties, amount of trapped fuel gases, and ventilation
Smoke indicators of backdraft
Pulsing smoke movement around small opening in the building, smoke-stained windows
Air flow indicators of backdraft
High velocity air intake
Heat indicators of backdraft
High heat, crackling or breaking sounds
Flame indicators of backdraft
Little or no visible flame
The effects of a back draft can vary considerably depending on a number of factors, including ___
- Volume of smoke
- Degree of confinement
- Temperature of the environment
- Pressure
- Speed with which fuel and air mix
Do not assume that a backdraft will always occur immediately after an opening is made into the building or involved compartment. You must watch ___ including the ___
- The smoke for indicators of potential rapid fire development
- Air currents changing directions or smoke rushing in or out
The violence of a backdraft depends upon the extent to which the ___
Fuel/air mixture is confined in the compartment
The more confined the fuel/air mixture is in the compartment, the ___ violent the backdraft will be
More
Occurs when the heat release rate of the fire has reached its peak, because of either a lack of fuel or oxygen
Fully developed stage
Two main types of fully developed fires
- Ventilation-limited
- Fuel-limited
The factor limiting the ___ is used to ID which type of fully developed fire exists
Peak heat release rate
Fully developed is often misinterpret “fully developed” to mean that the fire can no longer grow. A more accurate description would be that the fire has ___
Grown as much as it can
The most effective method of increasing the heat release rate in a fuel-limited fire is to ___
Provide more fuel
A campfire in a ring is an example of a ___ fire
Fuel-limited
A fuel-limited fire reaches its peak when ___
All the fuel becomes involved
Fuel-limited full development usually occurs when fires are not ___
Contained within compartments
If a fire becomes fuel-limited after a compartment has collapsed, firefighters have no choice but to ___
Protect surrounding exposures and contain the fire from the exterior
To reduce the risk of the unpredictable window failure, firefighters must transition the fire from ___
Ventilation-limited to fuel-limited
Even coordinated tactical ventilation increases the ___ in ventilation-limited fires
Combustion rate
___ alone will not transition a ventilation-limited fire to a fuel-limited fire
Additional ventilation
With the high heat of combustion found in modern furnishings, the only mechanism to transition the fire is to ___
Extinguish some of the burning fuel
If the amount of smoke exiting a window is no longer increasing, this indicates that the fire is ___
Consuming as much oxygen as it can through the window opening
A fire is said to be in the decay stage when ___
It runs out of either available fuel or available oxygen
In fuel-limited fires, the decay stage is usually the fire’s ___
Final stage
After a fuel-limited fire reaches the fully developed stage the fire will ___ as the fuel is consumed
Decay
As the fire consumes the available fuel and the heat release rate begins to decline, the fire enters the ___
Decay stage
Compartment fires rarely enter a state of fuel-limited decay unless the compartment ___
Burns all the way to the ground
If the compartment ___, then the amount of fuel available would limit the fire’s ability to grow
Fails and the fire opens to the atmosphere
To ensure that the decay stage of a ventilation-limited fire is the fire’s final stage, a ___ must take place
Controlled transition from ventilation-limited to fuel-limited
To provide the control the ventilation-limited fire’s transition to a fuel-limited fire, firefighters must ___
Cool the hot fire gases before any further ventilation occurs or immediately following any forcible entry
Cooling the hot fire gases before any further ventilation occurs will lessen the likelihood of the ___
Gases igniting when supplied fresh oxygen
If the compartment has not ventilation openings, the heat release rate will eventually decrease to the point that the heat in the compartment ___
Naturally transfers through the compartment itself to the outside
Fighting a fire in a structure, as opposed to a stand-alone compartment, is challenging because firefighters will need to ___
Size up the building, find the fire, and then find a way to attack the fire
Two regions of the flow path
- Ambient air flow in
- Hot exhaust flow out
The flow path is always ___ due to ___
- Unidirectional
- Pressure differences where the ambient air flows towards the seat of the fire and react with the fuel
The products of combustion flow ___
Away from the fire toward the low pressure outlet
In a structure fire, the ___ determine the available flow path
Floor plan and openings
A flow path’s effectiveness to transport ambient air to the seat of the fire is based on ___
- Size of ventilation opening
- Length of the path traveled
- Number or obstructions
- Elevation differences between the base of the fire and the opening
When hot gases follow the flow path from areas of high to low pressure, they ___ of the structure
Convect heat to a larger portion
Firefighters working in the exhaust portion of the flow path will feel the ___ in temperature as the velocity and/or turbulence increases, causing ___
- Increase
- Increased convective heat transfer
Similar to phenomenon to wind chill, except energy is transferred from a hot fluid to a solid surface rather than from a hot surface to a cooler fluid
Convective heat transfer
If ventilation is not well coordinated, the heat transfer associated with a flashover or backdraft, can be ___
Unsurvivable even when wearing PPE
The time that firefighters are operating in the flow path should be ___
Strictly limited
A structure fire that extends beyond the room of origin may have two compartments involved, each in different ___
Stages of development
Tactics employed for fire suppression, ventilation, and SAR will directly relate to the ___ occurring on a given incident
Fire dynamics
Beginning an attack on a ventilation-limited structure fire with ventilation alone will progressively ___ as additional vents are made
Increase the fire’s heat release rate and spread
Once the fire has filled the structure’s compartments with hot, unburned, gaseous fuel, using ventilation as the only tactic will not enable you to ___
Get ahead of the fire and limit fire growth and spread
Unplanned ventilation occurs when a ___
Structural member fails and introduces a new source of oxygen to the fir
Unplanned ventilation can result from the failure of a ___
- Window
- Roof
- Doorway
- Wall
Unplanned ventilation air does not have to come from ___
Outside of the structure
Unplanned ventilation is often the result of ___
- Occupant action
- Fire effects on the building
- Actions other than planned, systematic, and coordinated tactical ventilation
When unplanned ventilation occurs, ___ is essential to ensure your safety and that of other crew members
Situational awareness
___ can increase the pressure inside the structure, drive smoke and flames into unburned portions of the structure and onto advancing firefighters, and/or upset tactical ventilation efforts
The wind
You must be aware of the wind direction and velocity and use it to your advantage to assist in ___
Tactical ventilation
Wind speeds as low as ___ can create wind-driven conditions
10 MPH
Wind conditions can create differences in ___ that can cause windows to fail
Pressure
The exterior pressure on the upwind side of a structure will be ___ than the pressure on the downwind side
Higher
Occurs when a mixture of unburned fuel gases and oxygen comes in contact with an ignition source
Smoke explosion
Smoke explosions are violent because they ___
Involve premixed fuel and oxygen
Firefighters can influence fire dynamics in a number of ways including ___
- Temperature reduction
- Fuel removal
- Oxygen exclusion/flow path control
- Chemical flame inhibition
Using water or a foam agent to cool fire gases and hot surfaces for the purpose of extinguishment
Temperature reduction
Using door control and tactical ventilation techniques to control the amount of air available to the fire
Oxygen exclusion/flow path control
A strong wind can overpower the natural ___ of a fire and drive the smoke and hot gases back into the building
Convective effect
Two primary types of dangerous building conditions
- Conditions that contribute to the spread and intensity of the fire
- Conditions that make the building susceptible to collapse
Most building codes rate the various construction types according to ___
How long each construction type maintains its structural integrity over a certain period of time
___ provides the best indicators of structural integrity
Info gathered at the scene
The total quantity of combustible contents of a building, space, or fire area
Fuel load
Fuel load may be referred to as ___
Fire load
At a scene, you will only be able to estimate the fuel load based on ___
Your knowledge and experience
The ___ of a structure are often the most readily available fuel source
Contents
The chemical makeup of polyurethane foam and its ___ speed the process of fire development
High surface-to-mass ratio
Fuels located in the ___ level of adjacent compartments will pyrolize more quickly because of heat radiating from the hot gas layer
Upper
Continuous fuels such as combustible interior finishes will ___
Rapidly spread the fire through compartments
Fires originating on upper levels generally extend downward ___
Much more slowly
When the fire originates in a low level of a building, convected heat currents will cause vertical extension through ___
- Atriums
- Stairways
- Vertical shafts
- Concealed spaces
If the structural elements of the building become involved in the fire, not only does the structure itself provide a new source of fuel, but fire may be burning in ___
Hidden cavities throughout the building
Fires in hidden spaces increase the potential for ___
Building collapse
Assuming there is available oxygen, the higher the fuel load, the more likely the fire will behave in the following ways ___
- If structural members are part of the fuel load, structural integrity of the building will deteriorate faster
- The longer the fire burns, the more fire spread accelerates
- The fire may have a higher heat release rate
- The structure may self-ventilate, introducing even more oxygen to the fuel-limited fire and accelerating fire development and involvement of combustible structural members
Buildings with a greater amount of unburned fuel gases in the air because greater fuel packages pyrolized but did not begin combustion before the building became oxygen-limited are subject to ___ if ___
- Backdrafts and flashovers
- Firefighters do not coordinate ventilation
Interior finishes include ___
Window, wall, and floor coverings such as drapes, wallpaper, and carpet
Exterior wall coverings may add what type of fuel to the fuel load?
Carbon or petroleum fuels
The layout of the various open spaces in a structure
Building compartmentation
Any open space with no complete fire barrier dividing it
Compartment
Two rooms that a doorway connects are considered two compartments only if ___
The door between them is closed
Firefighters can take advantage of compartmentation to control the flow path to create ___
More predictable fire behavior
A structure fire is the place where ___ interact
Fire dynamics and building construction
Result of larger houses on smaller lots on newer construction
Reduced firefighter access and increasing potential exposure risks
Construction material and interior finishes consisting of synthetic materials and light composite wood components add to the ___ of the structure and contribute to the creation of ___ during a fire
- Fuel load
- Toxic gases
Because of energy-efficient designs, the structures tend to contain fire for ___, thus creating ___ environments
- A longer period of time
- Fuel-rich, ventilation-limited environments
Building characteristics to consider
- Occupancy classification
- Construction type
- Square footage and compartmentation
- Ceiling height
- Number of stories above and below ground level
- Number and size of exterior windows, doors, and other wall openings
- Number and location of staircases, elevator shafts, dumbwaiters, ducts, and roof openings
- External exposures
- Extent to which a building connects to adjoining structures
- Type and design of roof construction
- Type and location of fire protection systems
- Contents
- HVAC system
A fire in a large compartment will normally develop ___ than one in a small compartment
More slowly
Slower fire development in a larger compartment is due to the ___
Greater volume of air and the increased distance radiated heat must travel from the fire to the contents that must be heated
A large volume of air will support the development of a ___ before the lack of ventilation becomes the limiting factor
Larger fire
A high ceiling makes determining the extent of fire development more ___
Difficult
In structures with high ceiling, a large volume of ___ can accumulate at the ceiling level, while conditions at floor level ___
- Hot smoke and fire gases
- Remain relatively unchanged
Large open spaces that contribute to the spread of fire throughout can be found in ___
- Warehouses
- Churches
- Large atriums
- Large area mercantile buildings
- Theaters
In the concealed spaces under roofs, fire can ___
Travel undetected, feeding on combustible, exposed wood rafters
When smoke appears through opening in the roof or around the eaves, the exact point of origin may be ___
Deceiving
Thermal properties of a building
- Insulation
- Heat reflectivity
- Retention
Thermal property of insulation’s effect
Contains heat within the building which causes a localized increase in the temperature and fire growth and may introduce an additional fuel source
Thermal property of heat reflectivity’s effect
Increases fire spread through the transfer of radiant heat from wall surfaces to adjacent fuel sources
Thermal property of retention’s effect
Maintains temperature by slowly absorbing and releasing large amounts of heat
Unprotected engineered steel and wooden trusses can fail after ___ of exposure to fire
5 to 10 minutes
Unprotected engineered steel and wooden trusses can fail from ___
Exposure to heat alone without flame contact
Critical temperature at which steel begins to weaken
1000°F
___ in wooden trusses can fail quickly when exposed to heat
Metal gusset plates
The traditional wood-joist roof uses solid wood joists that tend to ___ when exposed to fire
Lose their strength gradually
A traditional wood-joist roof becomes ___ before failure, especially with a ___
- Soft or spongy
- Wood plank roof deck
Although a soft or sagging roof is an obvious indication of structural failure, it should not be considered the ___
Only sign of imminent collapse
More modern homes use engineered joists that burn more quickly and fail before the fire ___
Affects the roof decking
When the trusses fail first, entire pieces of decking may ___
Fall into the fire
With engineered trusses, until they fall, there may be no ___
Indication that a firefighter is in danger of falling through from sounding the roof or even standing on the roof
Observations about ___ are all key to establishing the safety of the roof
Fire’s location, its behavior, and activity, and the location of generated smoke
Floors above basement fires are especially prone to ___
Joist failures
An arched or curved roof outline often indicates a ___
Bowstring truss roof
Commonly used prior to 1960 for large commercial and industrial structures wherever large open floor spaces with limited interior supports were needed
Bowstring truss roof
Buildings that commonly used bowstring truss roofs
- Auto dealerships and repair facilities
- Bowling alleys
- Grocery stores
- Industrial complexes
Bowstring truss difference from other truss designs
- The compressional forces within the top chord act to force the load-bearing walls outward as well as downward
- The space between the trusses is greater
Bowstring truss roof systems constructed before 1960 have a common code deficiency: ___
The bottom chord members may have inadequate tensile strength to support code-prescribed roof loads
The risk of fire rises sharply when a structure is ___
Under construction, being renovated, or awaiting demolition
Inoperative ___ have become a contributing factor in fires in buildings under demolition
Standpipes and sprinkler systems
Buildings under construction are subject to rapid fire spread when they are partially completed because ___
Many of the protective features such as gypsum wallboard and automatic fire suppression systems are not yet in place as well as the lack of doors or other barriers
Buildings under construction with exposed wooden framing are often thought of as the equivalent of a ___
Vertical lumberyard
Potential contributors to the spread of fire in abandoned buildings or structures undergoing renovation or demolition ___
Breached walls, open stairwells, missing doors, and deactivated fire suppression systems
Arson is also a factor at construction or demolition sites because of ___
Easy access into the building
If good housekeeping is not maintained in a building undergoing renovation, accumulations of debris and construction materials can ___
Block exits
