Chapter 5 - Fire Dynamics (Workbook)

(T/F) Oxidation is a chemical reaction involving the combination of an oxidizer, such as oxygen in the air, with other materials.

True

(T/F) Potential energy is the energy that a moving object possesses.

False

(T/F) Energy cannot change from one type to another.

False

(T/F) Fire is an example of an exothermic chemical reaction.

True

(T/F) The autoignition temperature (AIT) of a substance is always lower than its piloted ignition temperature.

False

(T/F) Smoke and ash are examples of leftover fuel from incomplete combustion.

True

Temperature can be used to accurately predict and measure heat transfer.

False

Gases with a vapor density of less than 1 will sink.

False

Vapor pressure indicates how easily a substance will evaporate into air.

True

The orientation of a solid fuel relative to the heat source does not affect the way the fuel burns.

False

A visual indicator that a fire is leaving the incipient stage is flame height. 

True

During the growth stage, occupants can safely escape from the compartment, and a portable extinguisher or small hoseline can safely extinguish the fire.

False

Compartment fires rarely enter a state of fuel-limited decay unless the compartment burns to the ground.

True

Slower fire development in large compartments 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.

True

Prior to failing, plywood or oriented strand board (OSB) used for roof sheathing will show signs of sagging during a fire.

False

Metal gusset plates in wooden trusses can fail quickly when exposed to heat.

True

The risk of fire decreases when a structure is under construction, being renovated, or awaiting demolition.

False

The potential energy available for release in the combustion process is known as:

heat of combustion. (p. 134)

How is energy measured in the International System of Units (SI)?

Joules (J) (pg. 135)

The amount of heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit is defined as:

a British thermal unit (Btu). (pg. 135)

Converting water from a liquid to a gas (steam) is an example of what type of reaction?

Endothermic (pg. 136)

The off-gassing of a solid is a physical change known as:

Pyrolysis (pg. 136)

The fire tetrahedron model includes the chemical chain reaction to explain:

Flaming or gas-phase combustion. (p136)

When a mixture of fuel and oxygen encounters an external heat source with sufficient heat or thermal energy to start the combustion reaction, _____ occurs.

Piloted ignition (p.137)

Burning charcoal or smoldering wood is an example of:

nonflaming combustion. (p139)

What substance acts as a chemical asphyxiant and is often identified by coroners as the cause of death in civilian fatalities?

Carbon monoxide (CO) (p141)

What toxic and flammable substance is produced during combustion of materials containing nitrogen?

Hydrogen cyanide (HCN) (p141)

What type of heat transfer occurs when a solid material is heated as a result of direct contact with a heat source?

Conduction (p147)

The transfer of heat due to convection depends upon the area being heated, the temperature difference between the hot gas and the material being heated, and the:

turbulence and velocity of the moving gases. p148

The minimum temperature at which a liquid produces sufficient vapors to ignite, but will not sustain combustion in the presence of a piloted ignition source is the:

flash point. p153

What condition occurs when an extinguishing agent interferes with flaming combustion, forms a stable product, and terminates the combustion reaction?

Chemical flame inhibition. p.158

Which statement about entrainment based on the location of fuel packages is correct?

Fires in fuel packages near walls can only entrain air from two sides. p.162

Thermal layering is the tendency of gases to form into layers according to:

temperature, gas density, and pressure. p.163

The space between the air intake and the exhaust outlet, where the difference in pressure determines the movement of gases through the space describes the:

flow path. p.163

The total quantity of combustible contents of a building, space, or fire area is referred to as:

fuel load. p179

Any open space without a complete fire barrier dividing it is considered a(an):

compartment p.182

Which thermal property of a building increases fire spread through the transfer of radiant heat from wall surfaces to adjacent fuel sources?

Heat reflectivity p185

The thermal property of retention works in a building by:

maintaining temperature through slowly absorbing and releasing large amounts of heat. p.185

Occurs when a force is applied to an object over a distance or when a substance undergoes a chemical, biological, or physical change

work

The energy that a moving object possesses 

Kinetic Energy

Reactions that emit energy as they occur 

Exothermic Reaction

Comprises the world around you through physical materials that occupy space and have mass

Matter

Reactions that absorb energy as they occur 

Endothermic Reaction

The potential energy available for release in the combustion process

Heat of Combustion

A chemical reaction involving the combination of an oxidizer with other materials 

Oxidation

The capacity to perform work 

Energy

The amount of energy that an object can release at some point in the future

Potential Energy

Most common form of ignition, occurs when a mixture of fuel and oxygen encounters an external heat source sufficient enough to start the combustion reaction

Piloted Ignition p137

Form of ignition that occurs without any external flame or spark to ignite the fuel gases or vapors

Autoignition p137

Occurs slowly and at a lower temperature, solid phase combustion produces a smoldering glow in the material’s surface

Nonflaming Combustion p136-139

A physical change where a liquid changes into a gaseous state

vaporization p136-139

When heat transfers to a liquid or solid and the substance starts to convert to a gaseous state 

off gassing p136-139

A chemical change where, through heating, a solid begins to off-gas

Pyrolysis p136-139

Occurs when a gaseous fuel mixes with oxygen in the correct ratio and heats to ignition temperature

Flaming combustion p136-139

The most common source of heat in combustion reactions

Chemical energy p144

Energy created by friction and compression

Mechanical energy p146

A form of oxidation that increases the temperature of a material without adding external heat

Self-heating p144

The production of heat from electric current flowing through a conductor

Resistance heating p145

The energy released per unit of time as a fuel burns

Heat release rate (HRR) p143

The rate at which energy transfers

power p143

A high-temperature luminous electric discharge across a gap or through a medium

arcing p.146

The amount of heat transfer per unit area that is measured in kilowatts per square meter (kW/m2)

Heat flux p144

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 p153

The concentration above which combustion cannot take place or is too rich to burn

Upper flammable limit (UFL) p157

The temperature at which a liquid produces enough vapors that can be ignited and begin a sustained combustion reaction

Fire point p153

The minimum concentration of fuel vapor and air that supports combustion

Lower flammable limit p157

An indicator of how easily a substance will evaporate into air

Vapor pressure p.153

The extent to which a substance will mix with water

Solubility p154

Occurs when the fire consumes the available fuel or oxygen and the heat release rate (HRR) begins to decline

Decay stage p160

Occurs when a fire is small and confined to a portion of the fuel first ignited

Incipient stage p160

Describes a fire that does not have access to enough oxygen to continue to burn or to spread to all available fuels

Ventilation-limited p159

Occurs when all combustible materials in the compartment are burning and fire is consuming the maximum amount of oxygen that it can

Fully developed stage p160

Describes a fire with sufficient oxygen available for flaming combustion

fuel-limited

Describes the state of a fire when the initial fuel package becomes involved, the production of heat and smoke increases, and radiant heat may begin to pyrolyze nearby fuels

Growth stage