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
