ACCELERANT - A material, usually
a flammable to combustible liquid, which is used
to either initiate or hasten the spread of fire.
AFTERGLOW - The continued incandescent burning
of a fire after the flame has been extinguished.
ALGOR MORTIS - A Latin expression meaning
"Cooling of the body".
ALLIGATOR BLISTERS - Blisters on wood caused
by a fire whose look and texture resembles an alligator’s
ALTERNATING CURRENT - A polarity of current
which is reversed periodically, creating a regular
system of sine waves. Commonly known as AC current.
AMBIENT TEMPERATURE - The temperature of
AMPERE - A unit describing the rate of flow
of an electric current.
ANNEALING - A term used to describe the
effect heat has on the wire springs of a chair,
sofa, or vehicle seat. It causes the springs to
flatten out and lose their tension. Does not indicate
a liquid accelerant was present. May be the result
of a rapid or smouldering fire.
ARCING - When pure electricity jumps across
a gap in a circuit. The intense heat at the arc
may ignite any nearby combustible material or may
fuse the metal conductors.
AREA OF ORIGIN - The localized area where
a fire originated.
AUTOIGNITION - The spontaneous ignition
of gases or vapours given off by a heated material.
Synonymous with ignition temperature except that
no external ignition source is needed, since the
material has heated itself to its ignition temperature.
AUTOIGNITION TEMPERATURE -The lowest temperature
at which a combustible liquid or vapour can ignite
without the application of a flame or other means
BACKDRAFT - An explosion
or rapid burning of heated gases resulting from
the introduction of oxygen when air is admitted
to a building heavily charged by heat and smoke
from a fire, which has depleted the oxygen content
of a building.
BEADING - A process whereby a globule forms
on an electric wire during a fire or from a short
circuit. Laboratory analysis may be able to determine
if beading was the result of a fire or occurred
prior to fire commencement.
BI-METALLIC STRIP - A strip
consisting of two metals with different coefficients
of thermal expansion. When the strip is subjected
to heat, the lengths of the two faces alter by different
amounts, causing the strip to bend.
BLISTERING - Swelling caused by the expansion
of gas inside a material while it is still soft
or liquid due to heat. Can occur on painted surfaces
of materials when heated.
BLEVE - Boiling Liquid Expanding Vapour
BOILING POINT - The temperature where the
vapour pressure of a liquid is equal to that
of the surrounding atmosphere. The change of state
from liquid to vapour is accompanied by an absorption
of energy "the latent heat of vaporization."
BTU - British Thermal Unit. The quantity
of heat required to raise the temperature of 1 lb.
of water 1 degree Fahrenheit.
BURN PATTERN - The path of travel from a
fire’s point of origin.
BURNING - Normal combustion in which the
oxidant is molecular oxygen.
BURNING POINT - The temperature point at
which material produces enough vapours so that when
it is ignited, it will continue to bum.
BURNING RATE - The rate at which combustion
proceeds across a fuel. A specialized use of this
term describes the rate at which the surface of
a pool of burning liquid recedes. For gasoline,
this rate is reported to be approximately 1/4 inch
CARBONACEOUS - A material
made of or containing carbon. This encompasses practically
every combustible or flammable material.
CARBONIZATION - Decomposition by heat of
organic substance in a limited supply of air, accompanied
by a formation of carbon.
CARBON MONOXIDE - A gaseous molecule having
the formula CO, which is the product of incomplete
combustion of organic materials. Carbon monoxide
has an affinity for haemoglobin approximately 200
times stronger than oxygen’s and is highly poisonous.
CO is a flammable gas which bums with a blue flame,
and has explosive limits of 12% to 75%. Carbon monoxide
has approximately the same vapour density as air,
0.97 (air= 1.00)
CHAR - Carbonaceous material formed by the
incomplete combustion of organic materials, commonly
wood or cellulose based materials.
CHARCOAL - Residue from the destructive
distillation of wood which results when air is excluded.
It contains carbon and inorganic matter.
CHARRING - The formation of a light, carbonaceous
residue on wood or other organic matter, resulting
from incomplete combustion.
CHIMNEY EFFECT - The natural tendency of
heat to flow upwards.
CIRCUIT BREAKER - Safety device used to
open a faulty or overloaded electrical circuit.
COMBUSTIBLE LIQUID - Any
liquid having a flash point at or above 38 degrees
Celsius and below 93 degrees Celsius.
COMBUSTION - An exothermic
chain reaction between oxidizing and reducing agents,
or between oxygen and fuel. Combustion may occur
with any organic compound, or with certain combustible
elements such as hydrogen, sulphur, and finely divided
CONDUCTION - A physical
process where heat is transferred from one point
to another through an object.
CONDUCTIVITY - The ability
of a material to transfer energy from one place
to another. Thermal conductivity describes a substance’s
ability to transmit heat. Electrical conductivity
describes a substance’s ability to transmit electrical
current. Conductivity is the opposite of resistivity.
CONTINUITY - Maintaining
continuous surveillance at a fire scene from the
time of the fire until such a time when the investigation
is considered complete. Also used in electrical
descriptions such as the electrical circuit was
CONVECTION - Transfer of
heat by the movement of molecules in a gas or liquid,
with the less dense fluid rising. The majority of
heat transfer in a fire is by convection.
CREOSOTE - Tawny brown or
hard black internal deposits in a chimney produced
by burning wood.
CRYSTALLIZED - Tempered
glass that has broken into small squarish shaped
segments with rounded edges.
CURRENT - Measurement of
DIRECT CURRENT -A continuous
flow of current of the same polarity. Commonly referred
to as DC current.
OF TRAVEL - Denotes the direction the fire is
DOWNDRAFT - When a column
of air in the chimney reverses its direction.
DROP FIRE - A fire started
by flaming or glowing material failing from the
wall or ceiling to the floor area below.
DRYING OIL -An organic liquid
which, when applied as a thin film, readily absorbs
oxygen from the air and polymerizes to form a tough
elastic film. Linseed, tung, soybean and castor
oils are drying oils. Under certain conditions,
usually involving large surface areas and insulation,
such as a pile of rags soaked with drying oils,
spontaneous heating may occur.
ENDOTHERMIC REACTION - Chemical
reactions where during the formation of chemical compounds,
heat is absorbed. Nearly all endothermic compounds
are unstable and decompose easily. Explosives are
OF ACCIDENTAL CAUSES - The first step to recognizing
EXOTHERMIC REACTION - A
chemical reaction in which heat is given off during
the formation of chemical compounds. An example
is the heat given off during the formation of carbon
dioxide which is produced by the reaction of oxygen
with carbon during a fire. Most exothermic compounds
are stable, that is they cannot be easily decomposed.
EXPLOSIVE RANGE - The range of the percentage
of vapour concentration by volume in the air between
the upper and lower flammability limits.
FALSE CEILING - A ceiling suspended
some distance below the original.
FRONT - An additional facade on the front of
a building applied after the original construction.
FIBREBOARD - Building material made from
felted wood and other fibres and a suitable binder.
A generic term.
FIRE - The light and heat manifested by
the rapid oxidation of combustible materials. A
flame may be manifested but is not required.
FIRE BEHAVIOUR - The manner in which fuel
ignites, flames develop and heat and fire spread.
FIRE GAS - A gaseous product of combustion,
such as carton monoxide, carbon dioxide, hydrogen
FIRE PATTERN - A pattern, usually in a V
shape, with the apex of the V at the low point of
FIRE POINT - The lowest temperature at which
a liquid gives off sufficient flammable vapour to
produce sustained combustion after the removal of
the ignition source.
FIRE SEPARATION - A structural element made
in accordance to Building Code requirements so that
it will resist fire for a given period of time.
FIRE SPREAD - The development and travel
of fire across a surface or area.
FIRE WALL - A solid wall of masonry, capable
of resisting fire a specified period of time.
FLAMMABILITY - The relative ease with which
various fuels ignite and burn regardless of the
quantity of fuel involved.
FLAMMABLE LIQUID - A liquid with a flash
point below 38 degrees Celsius.
FLAMMABLE RANGE - The percentage of either
flammable vapour or gas concentrations in the ambient
air by volume at which combustion will take place.
FLAMMABLE VAPOUR - A vapour/air mixture
of any concentration within the flammability range
of that vapour.
FLASHOVER - The stage of a fire whereby
a room or other confined area becomes so heated
that the flames flash over and through the vapours
being produced by heated combustible contents in
FLASH POINT - The temperature at which a
liquid vaporizes to form an ignitable mixture with
FUEL LOAD - The total quantity of combustible
contents of a building, space, or fire area, including
interior finish and trim, expressed in heat units
or the equivalent weight in wood.
GYPROC - Generic term for
a wall sheathing material made of gypsum sandwiched
between paper covering. Usually ½" or 5/8"
HYDROCARBONS - Petroleum products
and natural gas are mixtures of several hydrocarbons.
IGNITION - The beginning of a
flame propagation or burning. The start of a fire.
IGNITION TEMPERATURE - The minimum temperature
to which a fuel must be heated in order to initiate
or cause self-sustained combustion independent of
another heat source.
INKBLOT PATTERN - Term used to describe
a liquid accelerant bum pattern.
KINDLING TEMPERATURE - The
ignition temperature of wood.
LIQUIFIED PETROLEUM GASES (LPG) - There
are three main categories: Propane, Butane and Pentane.
Derived from natural gas wells and oil refinery
MELTING POINT - The temperature at which
a substance passes from a solid into a liquid state.
MUSHROOMING - A condition in which fire
and heated gas rise to the uppermost point inside
a building or room and begin to build down laterally
to other areas.
OPEN FLAME - A visual flame that is usually
OVERHAULING - A process
involving the final extinguishment of embers after
the main body of a fire has been extinguished. Searching
for any remaining traces of fire and embers.
PETROLEUM PRODUCTS - Oils made by distilling
(heating) crude petroleum. It produces such products
as gasoline, kerosene and fuel oil.
- A condition which takes place between electrical
contacts when they are loose and energized. It can
cause the formation of copper oxide, which can resist
the flow of the current and cause overheating. Can
also occur in heated glass when subjected to sudden
cooling from water.
PLASTICS - A loose term used to designate
a wide range of substances which are capable of
being moulded. Commonly made from petroleum products.
POINT OF ORIGIN - The exact point where
a fire started.
PRIMARY FIRE - The established point of
origin of a fire.
PROBABLE CAUSE - Reasonable cause; having
more evidence for than against. A reasonable ground
for belief, given the known existing facts.
PROCESS OF ELIMINATION -The most useful
and efficient method of determining the origin and
cause of a fire.
PROPAGATION OF FIRE - The spreading of fire
from one point to another.
PUDDLING EFFECT - When a spilled liquid
accelerant flows to its lowest level due to gravity,
and then pools to form a puddle.
PYROLYSIS - The transformation of a substance
into one or more other substances by heat alone
PYROPHORIC ACTION - The chemical decomposition
of wood due to the continuous or intermittent application
PYROPHORIC CARBON - A carbonaceous composition
of wood which is caused by the continuous or intermittent
application of heat. A form of charcoal.
RADIATION FEEDBACK - Heat from a fire that
radiates back to the fuel causing increased vapour
RESISTANCE - The property
of a material which makes it resist the flow of
electricity through it.
SCORCHING - The early partial combustion of
a surface, usually due to exposure to a heat source.
SEAT OF THE FIRE - The area where the main
body of the fire is located, as determined by the
outward movement of heat and gases; where the fire
SECONDARY FIRE - A fire caused by a primary
fire, eg: a drop fire could cause a secondary fire
a considerable distance from the point of origin.
SHORT CIRCUIT - The convergence of two uninsulated
wires of different potentials.
SMOULDERING - To burn and probably smoke
without flame; to exist in a state of suppressed
activity. Can result in high heat release when oxygen
SPALLING - Destruction of a surface by frost,
heat, corrosion, or mechanical causes. Concrete
exposed to intense heat may spall explosively. Expansion
and contraction of the concrete as well as vaporizing
moisture contained in the concrete contribute to
this effect. It does not necessarily mean an accelerant
SPATTER EFFECT - When a liquid accelerant
is poured onto a floor and spatters or runs in finger
patterns. When ignited, it will burn in this pattern.
SPILL FIRE - The ignition and subsequent
combustion of a flammable or combustible liquid
inadvertently released from a container.
SPONTANEOUS COMBUSTION - A term normally
used to denote the chemical process of both spontaneous
heating and subsequent spontaneous ignition.
SPONTANEOUS IGNITION - Ignition and fire
due to the self-heating process encountered in certain
fires. The first onset of burning or fire in a combustible
material which has been heated without external
SPONTANEOUS IGNITION TEMPERATURE - The minimum
temperature at which the self-heating properties
of a substance can lead to ignition. Variations
can occur due to specimen size, rate of heat loss,
moisture content, etc.
SUBLIMATION - A change of state in a material
directly from a solid to a gas or from a gas to
a solid without passing through a liquid state concurrent
to a rise or fall-in temperature.
THERMAL COLUMN - Column of smoke and gases
given off by fires moving upwards because heated
gases expand and become lighter and rise. Chimney
TIMING DEVICE - A device used by an arsonist
to allow a fire to start electrically or mechanically
at a given time. Electric timers, hair dryers, clocks,
light bulbs and other devices are typical.
TRAILERS - Trails of fast burning materials
used by arsonists as fuses to rapidly spread a fire
throughout a structure or area.
UNDETERMINED - When there is one or more
probable fire causes, but none are conclusive.
UPPER LIMIT OF FLAMMABILITY - The highest
percentage of concentration by volume of flammable
vapour mixed with air which will bum with a flame.
VANITY FIRE - A fire set by an individual
to gain recognition, such as a watchman looking
for a promotion.
VOLATILE LIQUID - Liquid which has a tendency
to vaporize and evaporate.
V PATTERN - Characteristic cone-shaped pattern
left by a fire on a wall or other object at or near
its point of origin. Also, one which has developed
because of a secondary fire