Firefighter 1 Chapter 4 Test on Fire Dynamics
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Questions and Answers

Fires involve a heat producing chemical reaction between fuel and?

an oxidizer

When a substance changes from one type of matter to another, such as two or more substances combining to form compounds, the substance undergoes a?

chemical reaction

Which statement about energy and combustion is accurate?

A fuel's potential energy releases during combustion and converts to kinetic energy

Which element of the fire tetrahedron is included to explain flaming (gas phase) combustion?

<p>chemical chain reaction</p> Signup and view all the answers

What occurs when a mixture of fuel and oxygen encounters an external heat source with sufficient thermal energy to start the combustion reaction?

<p>piloted ignition</p> Signup and view all the answers

The minimum temperature at which a fuel in the air must be heated in order to start self-sustained combustion is known as the?

<p>autoignition temperature (AIT)</p> Signup and view all the answers

What causes flaming combustion to occur?

<p>A gaseous fuel mixes with an adequate amount of oxygen and heats to ignition temperature</p> Signup and view all the answers

What is the cause of most fire deaths?

<p>exposure to toxic gases found in smoke and/or lack of oxygen</p> Signup and view all the answers

Which statement about the dangers of products of combustion is accurate?

<p>Low oxygen concentrations alone can result in hypoxia or death</p> Signup and view all the answers

Which product of combustion acts as a chemical asphyxiant by excluding oxygen from the blood?

<p>carbon monoxide (CO)</p> Signup and view all the answers

Hydrogen cyanide (HCN) is a product of combustion that?

<p>targets the brain after being inhaled, ingested, or absorbed into the body</p> Signup and view all the answers

How does a compartment fire affect pressure in and around gases in the compartment?

<p>Heat from a fire increases the pressure of the surrounding gases</p> Signup and view all the answers

What is the measurement of the average kinetic energy in the particles of a sample matter?

<p>temperature</p> Signup and view all the answers

Which measurement is often used to measure how long PPE will protect a firefighter in an interior fire environment?

<p>heat flux to the PPE</p> Signup and view all the answers

What is the most common source of heat in combustion reactions?

<p>chemical energy</p> Signup and view all the answers

What may occur in an oxidation reaction when the heat generated exceeds the heat being lost?

<p>spontaneous ignition</p> Signup and view all the answers

Which type of electrical heating occurs when the current flowing through a conductor exceeds its design limits?

<p>overcurrent or overload</p> Signup and view all the answers

What occurs when a gas is compressed?

<p>heat is generated</p> Signup and view all the answers

The transfer of heat through and between solids is known as?

<p>conduction</p> Signup and view all the answers

In the fire environment, convection usually involves the transfer of heat through?

<p>the movement of hot smoke and fire gases</p> Signup and view all the answers

Which heat transfer mechanism is dependent on several factors including turbulence and velocity of moving gases?

<p>convection</p> Signup and view all the answers

By which mechanism of heat transfer does heat travel in a straight line at the speed of light?

<p>radiation</p> Signup and view all the answers

Heat that is radiated to the insulating air layer between PPE and your body?

<p>can cause heat stress and failure to PPE</p> Signup and view all the answers

A fuel's chemical content influences its heat release rate and its?

<p>heat of combustion</p> Signup and view all the answers

Gaseous fuels can be the most dangerous of all fuel types because they?

<p>are already in the physical state required for ignition</p> Signup and view all the answers

What will a liquid with a specific gravity of less than one do when combined with water?

<p>float</p> Signup and view all the answers

The minimum temperature at which a liquid gives off sufficient vapors to ignite, but not sustain combustion is its?

<p>flash point</p> Signup and view all the answers

What may occur if water is added to a burning liquid that is less dense than water?

<p>the water may disperse the burning liquid instead of extinguishing it</p> Signup and view all the answers

When solid fuels are heated, they begin to?

<p>pyrolize</p> Signup and view all the answers

Sawdust ignites more easily than a log because the sawdust has a higher?

<p>surface to mass ratio</p> Signup and view all the answers

In most compartment fires, the energy release in fire is directly proportional to the?

<p>amount of oxygen available for combustion</p> Signup and view all the answers

Materials that burn at normal oxygen levels will burn more intensely in?

<p>oxygen-enriched atmospheres</p> Signup and view all the answers

Combustion can occur within a range of concentration of fuel vapor and air; this range is referred to as the?

<p>flammable (explosive) range</p> Signup and view all the answers

How does the self-sustained chemical reaction influence the oxidation reaction in flaming combustion?

<p>increases the speed of the oxidation reaction</p> Signup and view all the answers

An extinguishing agent, such as dry chemical or Halon-replacement agent, terminates the combustion reaction by?

<p>interfering with the chemical chain reaction</p> Signup and view all the answers

Which statement describes the factor that MOST influences compartment fire development?

<p>whether the fire is fuel limited or ventilation limited</p> Signup and view all the answers

Fires develop through four stages: incipient, growth, ----- and decay.

<p>fully-developed</p> Signup and view all the answers

During the ----- stage of fire development, the three elements of the fire triangle come together and the combustion process begins.

<p>incipient</p> Signup and view all the answers

Which statement describes a fire in the incipient stage?

<p>the temperature is only slightly above ambient in areas that the fire, plume, and ceiling jet directly affect</p> Signup and view all the answers

In a compartment fire, the interface between the hot gas layers and cooler layer of air is commonly referred to as the?

<p>neutral plane</p> Signup and view all the answers

Which type of phenomenon occurs when the fire rapidly transitions from the growth stage to the fully developed stage?

<p>flashover</p> Signup and view all the answers

What happens during flashover?

<p>The volume of burning gases can increase to fill the room's entire volume and extend out of any openings from the room</p> Signup and view all the answers

In a compartment fire, smoke flashover indicators include rapidly increasing volume, turbulence, optical density and?

<p>darkening color</p> Signup and view all the answers

Observed from the exterior, a high neutral plane may indicate that the fire is in the early stages of development, or could indicate?

<p>a fire above your level</p> Signup and view all the answers

In a ventilation-limited compartment fire that has a large volume of flammable gases, opening a door or window could result in?

<p>backdraft</p> Signup and view all the answers

Which is an indicator for potential backdraft?

<p>pulsing smoke movement around small openings in the building</p> Signup and view all the answers

The ----- stage of fire development occurs when the heat release rate of the fire has reached its peak.

<p>fully-developed</p> Signup and view all the answers

A collapsed storage shed that is fully involved in flames would be an example of?

<p>fully-developed fuel limited fire</p> Signup and view all the answers

What is the likely result if additional air is allowed into an already-ventilated compartment fire?

<p>higher peak heat release rate</p> Signup and view all the answers

Which action will transition a compartment fire in a modern structure from ventilation-limited to fuel-limited?

<p>extinguishing some of the fuel load</p> Signup and view all the answers

A fire is said to be in the ----- stage when it runs out of either available fuel or available oxygen.

<p>decay</p> Signup and view all the answers

To ensure that the decay stage of a ventilation-limited fire is the fire's final stage, firefighters must provide a controlled transition by?

<p>cooling the hot fire gases before further ventilation occurs</p> Signup and view all the answers

The flow path of a structure fire is comprised of two regions: the ambient air flow in and the?

<p>hot exhaust flow out</p> Signup and view all the answers

What factor helps determine the flow path in a structure fire?

<p>the floor plan and openings within a structure</p> Signup and view all the answers

What will establish new flow paths between the fire compartment and exterior vents of the building?

<p>firefighters advancing a hoseline through an open door or ventilating windows to make entry into a building</p> Signup and view all the answers

Why must firefighters use tactics that control the oxygen available to the fire?

<p>to prevent unwanted fire spread</p> Signup and view all the answers

Firefighters working in the exhaust portion of the flow path will?

<p>feel the increase in temperature as the velocity and/or turbulence increases</p> Signup and view all the answers

What will occur if firefighters begin an attack on a ventilation-limited structure fire with ventilation alone?

<p>the fire's heat release rate and spread will progressively increase as additional vents are made</p> Signup and view all the answers

When a structural member such as a window or roof fails, introducing a new source of oxygen to a fire, ------ ventilation has occurred.

<p>unplanned</p> Signup and view all the answers

Which statement about ventilation and wind considerations is MOST accurate?

<p>wind can increase the pressure inside the structure, driving smoke and flames into unburned portions of the structure and onto advancing firefighters</p> Signup and view all the answers

What occurs when a mixture of unburned fuel gases and oxygen come in contact with an ignition source?

<p>smoke explosion</p> Signup and view all the answers

Which means of influencing fire dynamics is typically a tactic in wildland fires or liquid and gas fires?

<p>fuel removal</p> Signup and view all the answers

Using extinguishing agents other than water and foam to interrupt the combustion reaction is referred to as?

<p>chemical flame inhibition</p> Signup and view all the answers

Temperature reduction refers to using water or foam agent to cool fire gases and hot surfaces for the purpose of extinguishment?

<p>true</p> Signup and view all the answers

Oxygen exclusion/flow path control involves using door control and tactical ventilation techniques to control the amount of air on the fire?

<p>true</p> Signup and view all the answers

Most building codes rate construction types according to?

<p>how long each construction type maintains its structural integrity over a certain period of time</p> Signup and view all the answers

What provides the best indicators of structural integrity?

<p>information gathered at the scene</p> Signup and view all the answers

What is often the most readily available fuel source and significantly influences fire development in a compartment fire?

<p>contents within a structure</p> Signup and view all the answers

What is the most effective means of establishing awareness of hazards in commercial, industrial, and storage facilities with large fuel loads?

<p>performing and updating preincident surveys</p> Signup and view all the answers

In addition to structural members, what can be a significant factor influencing fire spread and loss of lives in fires?

<p>combustible interior finishes and furnishings</p> Signup and view all the answers

A compartment is any?

<p>open space with no complete fire barrier dividing it</p> Signup and view all the answers

What construction features tend to contain fires for a longer period of time?

<p>energy-efficient designs</p> Signup and view all the answers

Which statement BEST describes a fire in a large compartment or a compartment with a high ceiling?

<p>in structures with high ceilings, a large volume of hot smoke and fire gases can accumulate at the ceiling level, while conditions at floor level remain relatively unchanged</p> Signup and view all the answers

Fire spreading from a wall to a nearby couch due to radiant heat transfer is an example of?

<p>heat reflectivity</p> Signup and view all the answers

Insulation contains heat within the building which causes a localized increase in the temperature and fire growth?

<p>true</p> Signup and view all the answers

Retention maintains temperature by slowly absorbing and releasing large amounts of heat?

<p>true</p> Signup and view all the answers

The use of engineered or lightweight construction and trussed support systems pose a danger to firefighters because engineered trusses?

<p>can fail after 5-10 min of exposure to fire</p> Signup and view all the answers

Where might firefighters be MOST likely to encounter inoperative standpipes and sprinkler systems?

<p>buildings under demolition</p> Signup and view all the answers

Which type of buildings are subject to rapid fire spread because many of the protective features are not in place?

<p>buildings under construction</p> Signup and view all the answers

Study Notes

Fire Dynamics Overview

  • Fires are a heat-producing chemical reaction between fuel and an oxidizer.
  • A chemical reaction occurs when substances combine to form new compounds, such as with combustion.

Combustion and Energy

  • In combustion, a fuel's potential energy converts into kinetic energy upon burning.
  • Flaming combustion happens when gaseous fuel mixes with oxygen and reaches ignition temperature.
  • The autoignition temperature (AIT) is the minimum temperature needed for self-sustained combustion.

Fire Hazards

  • Most fire fatalities result from toxic smoke and oxygen deficiency.
  • Carbon monoxide (CO) acts as a chemical asphyxiant affecting the brain.
  • Hydrogen cyanide (HCN) also poses significant danger, directly targeting the brain upon exposure.

Fire Behavior in Compartment Fires

  • Heat from a fire increases gas pressure in the surrounding area.
  • Heat transfer through solid materials is called conduction; convection involves the movement of hot gases.
  • Radiation enables heat to travel in a straight line, even through vacuums.

Stages of Fire Development

  • Fires develop through four stages: incipient, growth, fully-developed, and decay.
  • Flashover is a rapid transition from growth to fully-developed stage, where burning gases fill the room.
  • A high neutral plane signals early fire stages or a fire located above ground level.

Fire Dynamics and Flow Paths

  • The flow path in a structure fire includes ambient air flowing in and hot exhaust gases flowing out.
  • Fire development is influenced by whether a fire is fuel-limited or ventilation-limited.
  • Unplanned ventilation occurs when structural components fail, introducing oxygen to a fire.

Ventilation Considerations

  • Wind can affect fire dynamics by increasing pressure within a structure.
  • Introducing additional air to a ventilation-limited fire can cause the heat release rate to peak dangerously.

Combustion Control Tactics

  • Fuel removal is typically used in wildland fires to influence fire dynamics.
  • Chemical flame inhibition interrupts the combustion process using agents besides water.
  • Cooling fire gases and applying controlled ventilation mitigate hazards during firefighting operations.

Construction and Fire Safety

  • Building codes classify construction types based on the time each type maintains structural integrity under fire.
  • Preincident surveys provide crucial information regarding hazards in structures, particularly those with combustible materials.
  • Lightweight construction poses risks due to potential rapid failure after short exposure to fire.

Additional Factors in Fire Spread

  • Insulation can trap heat, raising temperatures and fueling fire growth.
  • Buildings under demolition or construction often lack effective fire suppression systems, increasing fire spread risk.

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Description

Test your knowledge on fire dynamics from Chapter 4 of Firefighter 1. This quiz covers key concepts such as the chemical reactions involved in fires and the role of energy in combustion. Perfect for aspiring firefighters or those studying fire safety.

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