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Fire.org - glossary
Category: Agriculture and Industry > Fire
Date & country: 11/12/2007, UK
Words: 160


Absorption
1) A mechanical phenomenon wherein one substance penetrates into the inner structure of another, as in absorbent cotton or a sponge. 2) An optical phenomenon wherein atoms or molecules block or attenuate the transmission of a beam of electromagnetic radiation

Accelerant
Any material used to initiate or promote the spread of a fire. The most common accelerants are flammable or combustible liquids. Whether a substance is an accelerant depends not on its chemical structure, but on its use

Acetone
The simplest ketone. A highly flammable, water soluble solvent. Flash point of 0°F. Explosive limits of 2.6% to 12.8%

Adsorption
The adherence of atoms, ions or molecules of a gas or liquid to the surface of another substance. Finely divided or microporous materials having a large active surface area are strong adsorbents. Examples include activated carbon, activated alumina and silica gel

Alcohol
An organic compound having a hydroxyl (-OH) group attached. The lower molecular weight alcohols, methanol (CH3OH), ethanol (C2H5OH), and propanol (C3H7OH) are water soluble

Aliphatic
One of the main groups of hydrocarbons characterised by the straight or branched chain arrangement of constituent atoms. Aliphatic hydrocarbons belong to three subgroups: alkanes or paraffins, all of which are saturated and comparatively unreactive, the alkenes or alkadienes which are unsaturated (containing double [C=C] bonds) and more reactive, a…

Alkane
An aliphatic hydrocarbon having the chemical formula CnH2n+2 A normal alkane, or n-alkane is one which does not have a branched carbon backbone. An iso-alkane has a branched, rather than a straight chain, carbon backbone. Alkanes are also known as paraffins. The simplest alkanes are named as follows: CH4

Alkene
A straight chain, unsaturated compound of the olefin series which has the generic formula ..., having at least one double [C=C] bond. (See Aliphatic)

Alkyl Group
A functional group having the formula ... which may be attached to certain elements such as lead, silicon, or to other organic chemicals

Alkyne
An unsaturated aliphatic hydrocarbon characterised by the presence of a triple [C=C] bond. The generic formula for an alkyne is .... The most important member of this group is acetylene, HCCH, the first member of the series

Alloy
A solid or liquid mixture of two or more metals, or of one or more metals with certain nonmetallic elements, as in brass, bronze or carbon steel

Ambient
Pre-existing or normal environment

Aromatic
An organic compound having as part of its structure a benzene ring. (See Benzene). The term 'aromatic' as used in the fragrance industry is used to describe essential oils, which are not necessarily aromatic in the chemical sense

Arson
The crime of intentionally setting fire to a building or other property. This is a legal definition which may vary depending on the laws of a specific state

Atom
The smallest unit of en element which still retains the chemical characteristics of that element. An atom is made up of protons and neutrons in a nucleud surrounded by electrons. A molecule of water (H20) consists of two atoms of hydrogen and one atom of oxygen

Atomic Absorption
An analytical technique, used to determine the elemental composition and concentration of many metals and other inorganic elements. The material being analysed, generally in solution, is atomised, or broken up into individual atoms, usually by the action of extreme heat in a flame or small furnace. The ability of the atomised material to absorb cha…

Atomise
1) To break down into discrete atoms, usually by the application of extreme heat, as in atomic absorption, 2) To break a liquid into tiny droplets, as occurs in fuel injected engines or in the production of aerosol sprays

Attenuation
An adjustment of the signal amplifier response which results in the reduction of the electronic signal

Azeotrope
A mixture of two or more compounds which has a constant boiling point. The composition of the vapour above the azeotropic mixture has the same relative concentrations of compounds as does the boiling liquid. Azeotropic mixtures cannot be separated by fractional distillation

Benzene
A hexagonal organic molecule having a carbon atom at each point of the hexagon and a hydrogen atom attached to each carbon atom. Molecules which contain a benzene ring are known as aromatic. Benzene boils at 80°C and has a flash point of 12°F (-11°C). The explosive limits are 1.5% to 8% by volume in air

BTU
British Thermal Unit. The amount of heat energy required to raise the temperature of one pound of water one degree Fahrenheit. This is the accepted standard for the comparison of heating values of different fuels. One BTU equals 252 calories

Burning
Normal combustion in which the oxident is molecular oxygen

Burning Rate
The rate at which combustion proceeds across a fuel. A specialised use of this term, describes the rate at which the surface of a pool or burning liquid recedes. For gasoline, this rate is reported to be approximately ¼ inch per minute

Butane
A fuel gas having the formula C4H10. A constituent of LP gas. One pound of liquid butane produces 6.4 cubic feet of gas. One gallon of liquid butane weighs 4.87 pounds and produces 31 cubic feet of gas. One cubic foot of butane gas produces 3266 BTUs

Calorie
The amount of energy required to raise the temperature of one gram of water one degree Centigrade. One calorie equals 0.004 BTUs. One BTU equals 252 calories

Capillary
A narrow bore glass tube. Capillary column gas chromatography employs glass tubes having an inside diameter of approximately .2 to .5 millimetres and a length of 3 to 300 metres. The walls of a capillary column are coated with an adsorbent medium (a liquid phase in which the sample dissolves)

Carbon
The element upon which all organic molecules are based. Carbon has an atomic weight of 12.00, and occurs elementally in these forms: diamond, graphite and amorphous carbon such as coal or carbon black

Carbon Dioxide
A molecule consisting of one atom of carbon and two atoms of oxygen which is a major combustion product of the burning of organic materials. Carbon Dioxide (CO2) is the result of complete combustion of carbon. In the gaseous form, CO2 is used as a fire extinguisher. In the solid form, CO2 is known as dry ice. CO2 is heavier than air, with a vapour …

Carbon Disulfide
A highly flammable nonpetroleum solvent used for gas chromatography because of its relatively low signal generated in a flame ionisation detector. Carbon disulfide has the formula CS2. Reagent grade CS2 has an odour similar to rotten broccoli and can be ignited by contact with boiling water. It burns with a blue flame, providing CO2 and SO2 (sulfur…

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 oxygens and is highly poisonous. CO is a flammable gas which burns with a blue flame and has explosive limits of 12% to 75%. Carbon monoxide has approxima…

Carbon Tetrachloride
A nonflammable liquid having the formula CC14, formerly used as a fire extinguisher, and still used as a solvent and cleaning agent. Carbon tetrachloride boils at 77°C

Chain Reaction
A self-propagating chemical reaction in which activation of one molecule leads successfully to activation of many others. Most, perhaps all, combustion reactions are of this kind

Chemical Change
Rearrangement of the atoms, ions or radicals or one or more substances, resulting in the formation of new substances, often having entirely different properties. Also known as a chemical reaction

Chemistry
A basic science concerned with the structure and behaviour of atoms (elements); the composition and properties of compounds; the reactions that occur between substances and the resultant energy exchange and the laws that unite these phenomena into a comprehensive system.

Chromatogram
A series of peaks and valleys printed or written on a paper chart where each peak represents a component or mixture of two or more unresolved components in a mixture separated by gas or liquid chromatography

Chromatography
A chemical separation procedure which separates compounds according to their affinity for an adsorbent or absorbent material. Chromatography includes Thin Layer Chromatography (TLC), Liquid Chromatography (LC), Gas Chromatography (GC), (sometimes called Gas Liquid Chromatography or GLC) and High Performance Liquid Chromatography (HPLC)

Combustible Liquid
A liquid which is capable of forming a flammable vapour/air mixture. All flammable liquids are combustible. Whether a liquid is flammable or combustible depends on its flash point and on the agency definition relied upon. The Coast Guard classifies all liquid having a flash point over 80°F as combustible and liquids with a flash point below 80°F as…

Combustion
An exothermic chain reaction between oxidising and reducing agents, or between oxygen and fuel. combustion may occur with any organic compound, or with certain combustible elements such as hydrogen, sulfur and finely divided metals

Comparison Sample
1) A sample of material collected from a fire scene which is, to the best of the investigators knowledge, identical in every respect to a sample suspected of containing accelerant, but which does not contain accelerant. 2) A sample of suspected accelerant submitted for the purpose of comparing with any accelerant separated from a debris sample

Component
1) One of the elements or compounds present in a system such as a phase, a mixture, a solution or a suspension in which it may or may not be uniformly dispersed. 2) A compound or a group of unresolved compounds represented by a peak on a chromatogram

Compound
A chemical combination of two or more elements, or two or more different atoms arranged in the same proportions and in the same structure throughout the substance. A compound is different from a mixture in that the components of a mixture are not chemically bonded together. For example, a flask may contain two volumes of hydrogen (H2) gas and one v…

Concentration
the amount of a substance in a stated unit of a mixture or solution. Common methods of stating concentration are per cent by weight, per cent by volume, or weight per unit volume (eg: parts per million, billion, etc.)

Conduction
Passage of heat from one material to another by direct contact

Conductivity
The ability of a material to transfer energy from one place to another. Thermal conductivity describes a substances ability to transmit heat. Electrical conductivity describes a substances ability to transmit electrical current. Conductivity is to the opposite if resistivity

Control Sample
A sample of material which is known to be identical to a sample suspected of containing accelerant in every regard, except that the control sample does not contain accelerant. A known blank sample. In practical terms, control samples do not exist in the setting of a fire scene because (1) exact conditions during the fire cannot be duplicated from l…

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

Corrosion
The degradation of metals or alloys due to reaction with their environment. It is accelerated by acids, bases or heats

Cracking
A refining process involving decomposition and molecular recombination of organic compounds, especially hydrocarbons obtained by distillation of petroleum, by means of heat, to form molecules suitable for various uses such as motor fuels, solvent or plastics. Cracking takes place in the absence of oxygen

Deflagration
Vigorous burning with subsonic flame propagation. (See Detonation)

Desorption
the process of removing an adsorbed material from the solid on which it is adsorbed

Detonation
An exothermic chemical reaction which propagates through reactive material at supersonic speed

Diesel Fuel
Diesel Fuel consists mostly of hydrocarbons ranging from C10 to C24. The composition of diesel fuel may vary with changes in latitude or changes in season. this variability is provided by the refinery to control the volatility of the product. In order to be identified as diesel fuel, a sample extract must exhibit a homologous series of five or more…

Distillation
A separation process in which a liquid is concerted to a vapour and the vapour is then condensed back to a liquid. The usual purpose of distillation is separation of the compounds of a mixture. Steam distillation separates all water insoluble liquids from solids and water soluble compounds in a mixture

Drying Oil
An organic liquid which, when applied as a thin film, readily absorbs oxygen from the air and polymerises 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

Electron
A negatively charged subatomic particle which circles the nucleus of the atom in a cloud. Most chemical reactions involve the making and breaking of bonds held together by the sharing of electrons

Electron Capture Detector (ECD)
A type of gas chromatographic detector which is sensitive to halogenated hydrocarbons and other molecules capable of easily gaining an electron. Electron capture is not generally used for hydrocarbon detection

Element
One of 106 presently known kinds of substances that comprise all matter at and above the atomic level. (See Periodic Table)

Elution
the process of removing absorbed materials from the surface of an adsorbent such as activated charcoal. the solvent in this process is called the eluant

Emission Spectroscopy
The study of the composition of substances and identification of elements by observation of the wavelengths of radiation emitted by the substance as it returns to a normal state after excitation by an external source. Generally used for elemental analysis

Emulsion
A stable mixture of two or more immiscible liquids in suspension

Endothermic Reaction
A chemical reaction which absorbs heat

Ethane
A simple alkane having the formula C2H6. A minor component of natural gas. Its explosive range is 3% to 12.5%. Ethane has approximately the same vapour density as air

Ethanol
Ethyl alcohol. Grain alcohol. Flammable, water soluble alcohol. Flash point of 55°F. Explosive limits of 3.3% to 19%

Ether
Diethyl ether, ethyl ether. A highly flammable solvent which can form explosive peroxides when exposed to air. Flash point of -49°F. Explosive range of 1.85% to 48%

Ethylbenzene
A component of gasoline, but also a major breakdown product or pyrolsis product given off when certain polymers are heated

Eutetic
the lowest melting point of an alloy or solution of two or more substances (usually metals) that is obtainable by varying the percentage of the components. Eutetic melting sometimes occurs when molten aluminium or molten zinc comes in contact with solid steel or copper

Evaporation
Conversion of a liquid to the vapour state. See also vaporisation

Evaporation Rate
A measure of the quantity of a liquid converted to vapour in a unit of time. Among single component liquids, the rate varies directly with the surface area, the temperature and the vapour pressure, and inversely with the latent heat of vaporisation of the liquid

Exothermic Reaction
A chemical reaction which evolves heat. Combustion reactions are exothermic

Explosion
The sudden conversion of chemical energy into kinetic energy with the release of heat, light and mechanical shock

Explosive Limit
Flammability limit. The highest or lowest concentration of a flammable gas or vapour in air that will explode or burn readily when ignited. The limit is usually expressed as a volume percent of gas or vapour in air

Explosive Range
Flammability range. The set of all concentrations between the upper and lower explosive limits of a particular gas or vapour

Extraction
A chemical procedure for removing one type of material from another. Extraction is generally carried out by immersing a solid in a liquid, or by shaking two immiscible liquids together, resulting in the transfer of a dissolved substance from one liquid to another. Solvent extraction is one of the primary methods of sample preparation in arson debri…

Fire
The light and heat manifested by the rapid oxidation of combustible materials. A flame may be manifested but is not required

Fire Point
The temperature, generally a few degrees above the flash point, at which burning is self-sustaining after removal of an ignition source

Fire Tetrahedron
Fuel, heat, oxygen and a chemical chain reaction

Fire Triangle
Fuel, heat and oxygen

Flame
A rapid gas phase combustion process characterised by self-propagation

Flame Ionisation Detector (FID)
A nearly universal gas chromatographic detector. It responds to almost all organic compounds. An FID does not respond to nitrogen, hydrogen, helium, oxygen, carbon monoxide or water. This detector ionises compounds as they reach the end of the chromatographic column by burning them in an air/hydrogen flame. As the compounds pass through the flame, …

Flame Propagation
Travel of a flame through a combustible gas/air or vapour/air mixture

Flammability Limit
(See Explosive Limit)

Flammability Range
(See Explosive Range)

Flammable Liquid
A combustible liquid that has a flash point below 80°F according to the Coast Guard, 100°F according to the NFPA. Liquids having a vapour pressure over 40 pounds per square inch at 100°F are classified as flammable gases. Flammable liquids are a special group of combustible liquids

Flammable Vapour
A vapour/air mixture of any concentration within the flammability range of that vapour

Flash Fire
A fire that spreads with unusual speed, as one that races over flammable liquid of through combustible gases

Flash Point
The temperature at which a pool of liquid will generate sufficient vapours to form an ignitable vapour/air mixture. The temperature at which a liquid will produce its lower explosive limit in air. Flash point describes one of several specific laboratory tests. Frequently materials can be made to burn below their flash point if increased surface are…

Fractionation
The separation of one group of compounds in a mixture from another, generally by distillation

Fuel Oil
A heavy petroleum distillate ranging from #1 (kerosene or range oil), #2 (diesel fuel), up through #6 (heavy bunker fuels). To be identified as fuel oil, a sample must exhibit a homologous series of normal alkanes ranging from C9 upward

Gas Chromatography
(also known as Gas Liquid Chromatography): The separation of organic liquids or gases into discrete components or compounds seen as peaks on a chromatogram. Separation us done in a column which is enclosed in an oven held at a specific temperature, or programmed to change temperature at a reproducible rate. The column separates the compounds accord…

Gasoline
A mixture more than 200 volatile hydrocarbons in the range of C4 to C12 , suitable for use in spark ignited internal combustion engine. Regular automotive gasoline has a flash point of -40°F

Headspace Concentration
A technique for concentrating all or most of the flammable or combustible liquid vapours in a sample onto a tube of charcoal, a wire coated with charcoal, a charcoal coated polymer, or some other adsorbing material which will later be desorbed in order to analyse the concentrated vapours. This is a primary form of sample preparation in arson debris…

Heat
A mode of energy associated with and proportional to molecular motion that may be transferred from one body to another by conduction, convection or radiation

Heptane
An alkane having the formula C7H16, flash point of 25°F and explosive limits of 1.2% to 6.7%

Hexane
An alkane having the formula C6H14. Flash point -9°F. Explosive limits of 1.2% to 7.5%

Homologous Series
A series of similar organic compounds, differing only in that the next higher member of the series has an additional CH2 group (one carbon atom and two hydrogen atoms) in its molecular structure. Fuel oils are characterised by the presence of an identifiable homologous series of normal alkanes

Hydrocarbon
A organic compound containing only carbon and hydrogen

Hydrogen
The simplest element. Atomic Number 1. Hydrogen gas has a specific gravity of 0.0694 (air = 1), so it is much lighter than air. Hydrogen is highly flammable, forming water upon combustion. Explosive limits are 4% to 75%

Ignition
The means by which burning is started

Ignition Temperature
The minimum temperature to which a fuel must be heated in order to initiate of cause self sustained combustion independent of another heat source

Immiscible
Describes substances of the same phase or state of matter (usually liquids) that cannot be uniformly mixed or blended