Fire Insurance Investigators - Arson, Investigations

Fire and Arson Investigation Services for Massachusetts, Connecticut, Rhode Island, and New Hampshire
Robert Corry is a licensed, bonded and insured Private Detective in MA, CT, and NH

Fifty Terms to know in Fire, Arson and Explosion Investigation Reports

Accelerant. A substance used to initiate or promote the spread of fire. The most commonly encountered arson accelerants are ignitable (flammable or combustible) liquids although many common combustibles such as cardboard boxes are used occasionally to accelerate fire propagation.
Ignitable liquids that are used as fire accelerants share a number of common properties. The most common liquid accelerants generate heavier than air, ignitable vapors at ordinary temperatures, float on water, sheen and are immiscible (don’t mix with water).
Fire and Arson Investigators who want to improve their skill at expertly recognizing and collecting samples of ignitable liquids used as fire accelerants can obtain a copy of A Pocket Guide to Accelerant Evidence Collection, 2nd Edition at www.arsonguide.com.
Training in taking these samples is available on www.interfire.org.
Accident. An unplanned, unintentional event or chance occurrence usually arising from carelessness or ignorance.
Annealing. Loss of temper in metal caused by heating.
Area of Origin. The room or area where a fire began.
Arson. The intentional or reckless setting of a fire with intent to cause damage or defraud an insurer.
Auto-ignition temperature. The lowest temperature at which a combustible material ignites in air without a spark or flame. Auto-ignition temperature is also referred to as the spontaneous ignition temperature.
BLEVE. Boiling Liquid Expanding Vapor Explosion. A mechanical explosion caused by heating of a liquid in a sealed container.
Brisance. The amount of shattering effect produced by a high explosive.
Cause. A person who acts or a thing that occurs so as to produce a specific result. The circumstances, conditions or agencies that brought about or resulted in a fire or explosion.
Calcination. A term used by fire and arson investigators to describe changes in gypsum wallboard during a fire. Exposure to intense heat results in loss of free and chemically bound water in wallboard which produces color changes and deterioration in structural strength. The amount of calcination can be plotted by a fire investigator revealing local ‘hotspots’ in much the same way that wood framing can be used.
Cause. NFPA 921 Guide to Fire and Explosion Investigation (2004 Edition) defines accidental, natural, incendiary or undetermined as the four permissible classifications of fire cause.
Cellulosic. Plant based materials such as wood, cotton, paper, etc. The term is fire investigation reports generally refers to structural, finish or contents made from wood and wood by-products which become involved in the fire.
Clean burn. An area of wall or ceiling where charred organic residues such as soot have been burned away by direct flame impingement or intense radiational heating leaving a local area that a fire investigator would recognize as generally lighter in appearance than surrounding surfaces.
Code v. Guide. The National Fire Protection Agency produces two categories of manuals governing many activities related to fire protection including investigation.
One category is a “Code” and the second category is a “Guide.” A Code is a mandatory standard whereas a Guide is described by the NFPA as an advisory or informative document containing only non-mandatory provisions.
Combustible liquid. An ignitable liquid having a flash point at or above 100 degrees F (Fahrenheit).
Crazing. Stress cracks in glass as the result of rapid cooling in a hot environment.
Deflagration. A rapid combustion reaction proceeding through fuel at a sub-sonic speed (typically less than 3300 feet per second). Deflagrations often occur in ignitable vapors or combustible dust.
Detonation. An extremely rapid reaction proceeding through material at supersonic (3300 feet per second or greater) rates accompanied by high temperature, intense pressure increase, shock wave producing specific effects.
Detonations are usually associated with high explosives such as PETN or TNT.
Explosive limits (flammable limits). The extreme lower and upper concentrations of an air/gas mixture in which combustion or deflagration is supported. Generally, fuels with broad flammable/explosive limits such as acetylene (2.5% to 80% by volume) are considered more hazardous.
The explosive limit for gasoline is stated to be 1.4% to 7.6%. Fire investigators know that this is a value established under laboratory conditions at 1 atmosphere of pressure and at 32 degrees F.

Increases in temperature and pressure result in lower LEL and higher UEL approaching 100% whereas a lower pressure and temperature has the opposite effect.

The manner in which an ignition of ignitable vapors presents itself provides a clue as to the range. Ignitions at the LEL tend to be sharp with little smoke. At the UEL the ignition tends to produce a more muffled sound accompanied by a lot of smoke.

Toward the center of the explosive range the possibility increases of a high order explosion.
Fire. Rapid oxidation with the evolution of heat and light of varying degrees. Fire is an exothermic reaction (emergency is released). Flaming fire is always a gas phase reaction – meaning one or more ignitable gases are combining with a gaseous oxidizing agent in the flame zone forming new compounds.
Fire load. The total amount of fuel that might be involved in a fire measured by the amount of heat that might be developed.
Fire investigators must carefully document the location, type and quantity of potential fuel packages in the area of fire origin to determine fire load.
Flashover. A transition phase in a compartment fire in which surfaces exposed to thermal radiation reach ignition temperature more or less simultaneously and fire spreads rapidly throughout the space resulting in full room involvement.
Fire Science. The body of knowledge concerning the study of fire and related subjects (such as fire and explosion chemistry, heat release, fluid mechanics, fire safety, etc.) and their interaction with people, structures and the environment.
Gas Chromatography. A laboratory test method that vaporizes mixtures by heating and then separates individual components according to boiling points and molecular weights.
Ghost marks. Stained outlines of floor tiles produced by dissolution and combustion of tile adhesive.
Heat transfer. The spread of thermal energy by convection, conduction and radiation.
Heat Release Rate (HRR). The rate at which heat energy is generated by burning.
Ignition. The process of initiating self-sustaining combustion.
Ignition temperature. The minimum temperature a substance should attain in order to ignite under test conditions.

Under ordinary conditions a ‘competent ignition source’ must have sufficient temperature and energy to raise the temperature of available fuels at the fire origin to their ignition temperature.

The major objective of a fire investigator during an origin and cause examination is to accurately determine the origin of the fire and then examine that spot for potential sources of ignition. The potential ignition scenarios are then evaluated to determine if they are capable of creating sufficient heat energy to cause combustion of fuels present there.

If a fire & arson investigator identifies the wrong point of origin it almost always follows that any source of ignition identified will also be incorrect.

Ignition sequence. This term described identification of a sequence of events that brings together a competent source of ignition with a suitable fuel.
Ignitable liquid. Any liquid capable of fueling a fire.
For a list of the twenty-five most common ignitable liquids found in U.S. arson scenes along with their physical properties obtain a copy of The Pocket Guide to Accelerant Evidence Collection, 2nd Edition at www.arsonguide.com or search www.interfire.org.
Intentional act. Deliberate behavior.
Arson investigators recognize that virtually every human initiated fire is an ‘intentional act.’ The difference between an arson fire and an accidental or purposeful ‘intentional’ fire (igniting a stove top element on a gas range, burning slash, etc.) lies in the investigator establishing the intent of the responsible party.

Spreading ignitable liquids, rearranging combustibles to create a fire load, threats to set a fire followed by the setting of a fire are examples of malicious intent.
Flammable liquid. An ignitable liquid having a flash point below 100 degrees F (Fahrenheit) under laboratory conditions. Flammable liquids are a class of combustible liquids.
Flash Point. The lowest temperature at which a given ignitable liquid produces an ignitable vapor in a laboratory test.
Layering. The systematic process of a fire investigator carefully removing collapsed debris from the top to identify the location and structure of artifacts beneath.
Nonflammable. Materials that will not burn under normal circumstances.
Pyrolysis. The chemical decomposition of a compound by heat alone. Pyrolysis often precedes combustion.
Overhaul. A stage in firefighting operations where a search is made for hidden fire or glowing combustion. This is done by removing furniture and opening walls and ceilings.

Poorly managed firefighting tactics and overhaul are often cited as major reasons for the inability of fire investigators to determine origin and cause or prove a crime.

Origin & Cause Examination. One phase in a fire investigation.
This portion of the fire investigation seeks to identify the origin then the cause of a fire. This process depends on the skill of the fire investigator to recognize and correctly interpret fire patterns to identify the specific location where a fire initiated and developed.

If the origin is correctly located the evidence establishing the cause of the fire will be there.
Oxidation. Generally any reaction in which electrons are transferred. In most fire cases atmospheric oxygen gains electrons and fuel atoms lose electrons.
Plume. The convective column of hot gases produced by a flame.
Rekindle. Re-ignition of a fire from latent heat, sparks or embers.
Salvage. A stage in firefighting operations where contents of a fire building are removed or covered to protect them from incidental damage.
Scientific Method. The systematic pursuit of knowledge involving the recognition and formulation of a problem, the collection of data through observation and experimentation and the formulation and testing of a hypothesis.
Spalling. Crumbling or fracturing of a concrete or brick surface as a result of exposure to mechanical or thermal stress.
Spontaneous combustion (self heating). The process whereby a material increases in temperature without drawing heat from its surroundings.
Stoichiometric mixture. A mixture containing an optimal ratio of fuel and oxygen. Gaseous fuel-air mixtures can result in an explosion when a stoichiometric mixture exists.
Vapor. The gaseous phase of a liquid or solid.
Vapor density. The ratio of the weight of a given volume of gas or vapor to that of an equal quality of dry air.
Volatility. The ease with which vapors are given off.