Fire behavior and combustion
The minimum ignition energy (MIE) of most hydrocarbons is:
.25 mJ.
What is the approximate average number of firefighters killed in the line of duty each year from 2000-2010?
100
From 2002-2011 approximately how many civilians were killed by fire each year?
3,000-4000
How many firefighters died in the Sofa Super Store fire in 2007 due to lack of understanding of fire dynamics?
9
What is a premixed flame?
A flame where air is introduced before the point of combustion
What is a laminar flame?
A flame with a clearly defined combustion zone
What is a turbulent flame?
A flame with oxidation occurring within a generalized area but not in a steady geometric pattern
The open cup test of a liquid's flash point involves which of the following?
A heating unit being adjusted to raise the liquid's temperature slowly The operator recording liquid temperature periodically, then introducing a pilot flame across the surface The flash point being recorded as the temperature that occurred immediately before a flash fire is witnessed
NFPA 921 defines fire as which of the following?
A rapid oxidation process, which is a chemical reaction, resulting in the evolution of heat and light in varying intensities
Which of the following describes an endothermic reaction?
Absorbs energy/heat
Which choice describes the endothermic process of pyrolysis?
Absorbs heat/energy
What is the heat of gasification?
Amount of energy that is required to produce a unit mass of flammable vapor from a combustible that is initially at ambient temperatures
What defines a gaseous state?
Atoms that collide but are not in a fixed arrangement and assume the shape of a container
Flame spread of the soundproofing used at the Station Night Club was known to fire-testing agencies and professionals, but was not considered during which phase?
Both Installation and Fire code inspection
Smoldering combustion is characterized by which of the following?
Both Oxidation reaction in the solid phase that produces light and Oxidation reaction in the solid phase that produces heat
Heat release rates of pool fires are dependent on which of the following?
Both Surface area exposed to air and Heat of combustion of the fuel
How will the presence of char affect the burning rate of a fuel?
Burning rates will be slowed, and the energy required increases.
A Class K fire involves what types of materials?
Certain cooking media such as vegetable and animal fats and oils
What is the term for carbonaceous material that has been burned or pyrolyzed and has a blackened appearance?
Char
Under NFPA classification, which of the following presents the most significant threat of producing ignitable vapors at ambient conditions?
Class IA
Under NFPA classification, which of the following presents the least significant threat of producing ignitable vapors at ambient conditions?
Class IIIB
A Class D fire involves what types of materials?
Combustible metals
________, including butadiene and neoprene, are items that have been created to match the properties of natural rubbers.
Elastomers
Under the Federal Hazardous Substances Act, ignitable liquids are classified as which of the following?
Extremely flammable, flammable, or combustible
A Class B fire involves what types of materials?
Flammable gases and flammable or combustible liquids
What is a class 4 hazardous material per the U.S. Department of Transportation?
Flammable solid
What is the main measurement used when considering the ignitability of liquids?
Flash point
________ are plastics created with pockets of air throughout the fuel.
Foams or cellular plastics
The fire triangle consists of which of these components?
Fuel Heat Oxygen
Fire protection professionals must utilize a full knowledge of what topics?
Fuels and fuel geometry Detection Suppression
Which of the following describes an exothermic reaction?
Gives off energy/heat
________ is used to describe the amount of energy that is required to produce a unit mass of flammable vapor from a combustible that is initially at ambient temperatures.
Heat of gasification
Why do aerosols ignite so easily?
High surface to mass ratio
The energy required to change a liquid to a vapor is termed what?
Latent heat of vaporization
What is a liquid's flash point?
Lowest temperature of a liquid, as determined by specific laboratory tests, at which the liquid gives off vapors at a sufficient rate to support a momentary flame across its surface
Which of the following sets a basis for classification of flammability of liquids?
NFPA 30
A Class C fire involves what types of materials?
Natural and synthetic materials like rubber and plastics, which are energized by electrical circuits, wiring, motors, and other equipment
Should the combined gas law be used to calculate the pressure in a BLEVE?
No, due to the high pressure and unknown quantities of vapor/liquid in the container
A Class A fire involves what types of materials?
Ordinary cellulosic materials such as wood and paper as well as similar natural and synthetic materials like rubber and plastics
What are fire investigators primarily tasked with identifying?
Origin, cause, spread, responsibility, and circumstances
What is the major source of fuel in upholstered furniture?
Polyurethane foam
What is the term used to describe the evaluation of conditions before emergencies?
Preplanning
Having definite shape and volume describes what state of matter?
Solid
The standard time-temperature curve does not take into account what kinds of fuels that are common today?
Synthetic materials
What is a liquid's fire point?
Temperature at which the substance must be raised to produce sufficient vapors to sustain burning after the initial flash
Flammability limits are dependent on which of the following?
Temperature, pressure, and oxygen concentration
What is the effective heat of combustion?
The actual amount of energy that is released when fuel oxidizes in air
What is a stoichiometric mixture?
The exact proper mixture (mass of each reactant) of chemical for a chemical reaction
What is the upper explosive limit?
The highest percentage of fuel to air where combustion can occur
What is the lower flammable limit?
The percentage of air and fuel where the lowest amount of fuel will combust
Miscibility and solubility are terms used interchangeably to describe which of the following?
The tendency of materials to become solutions or to retain their initial characteristics
What is a flame?
The visible, luminous body where the oxidation reaction is occurring
What is one factor responsible for the rapid fire development in today's built environment?
The volume of commodities and synthetics
Nearly all metals burn under the right conditions.
True
What term describes the pressure exerted by vapors leaving the liquid surface?
Vapor pressure
The autoignition temperature of liquids is which of the following?
Well above the boiling point Ignition absent of an ignition source Identified by raising the temperature of a liquid in a controlled environment until ignition occurs
Increasing the oxygen concentration causes:
an increase in temperature.
The temperature to which a mixture of fuel gas and air must be raised to initiate combustion without any external heat source is called:
autoignition temperature.
Three known conditions that can lead to firefighter fatalities are flashover, rollover, and:
backdraft.
Flammable liquids have a flash point (per NFPA 30):
below 100 degrees Fahrenheit.
Fire prevention professionals involved in inspections are charged with identifying conditions that:
exceed design criteria for fire protection systems. adversely affect passive fire protection elements. hinder active fire protection and detection element
Melting is a physical change of a substance:
from solid to liquid.
Caution should be used when evaluating gasses because:
gases not listed as flammable can sometimes ignite under certain conditions.
The ________ of a material refers to the amount of energy emitted per unit of fuel mass consumed, and it varies by fuel.
heat of combustion
The rate at which the heat energy is generated by burning is termed:
heat release rate.
Cellulosic materials consist of all of the following EXCEPT:
hydrocarbons.
Liquids evolving vapors that can undergo combustion with relative ease are considered to be:
ignitable liquids.
The variables considered when determining a fuel's heat release rate include all of the following EXCEPT:
ignition temperature.
The four ideal fire growth curves include all of the following EXCEPT :
infinite.
The predominant factor that led to the large number of deaths at the Cocoanut Grove fire was:
inward swinging doors.
The ________ is the loss of mass over time from the fuel's surface when undergoing combustion.
mass burning flux ( )
The ________, often referred to as the burning rate, is the rate at which the fuel is losing mass while undergoing combustion and is usually expressed in kilograms per second (kg/s) or grams per second (g/s).
mass loss rate ( )
Temperature is a measurement of:
molecular movement.
Investigators must first seek the ________ and then the ________ of a fire in order to ascertain what happened.
origin; cause
Study of fire dynamics helps to:
provide safety for humans and structures.
Solids undergo ________ as they chemically break down to become fuel gasses that can burn in the gas phase.
pyrolysis
As altitude changes, the vapor pressure of a liquid:
remains the same.
Smoke is defined as:
the gases, vapors, and small particles that come off from a burning substance.
The term fire dynamics refers to:
the interrelationship of fuel, heat, oxygen, chemical reactions, and the physical world.
Flame spread refers to:
the speed with which the flame front (oxidation zone) moves across a fuel's surface.
Plastics that are not cured or hardened during the manufacturing process and that soften and melt when exposed to heat are:
thermoplastics.
Plastics that have been hardened into a defined shape during manufacturing and that when heated will typically not soften or melt but produce char, are called:
thermosetting plastics.
Specific gravity of vapors and gases is termed:
vapor density.
