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Fire accelerants and arson
Fire and accelerants.
When a fuel is ignited in the presence of oxygen, a chemical reaction takes place giving off energy in terms of heat. During this chemical process some energy is also given off in the form of light which is of various colors depending on the amount of heat energy given off. This combination of energy in terms of heat and light given off is referred to as fire. The flame which is the visible part of the fire has different colors depending on the type of fuel involved and the amount of oxygen available for combustion.
Three key elements are necessary for a fire to start and spread effectively. These key elements which make up the fire triangle include heat, oxygen and fuel. The absence of one of the element from the fire triangle leads to the fire getting extinguished. The fire triangle was developed to try and come up with a way of combating fire considering the danger and disasters posed by fires that at times get out of hand. Firefighters have generally developed a concept using the fire triangle that enables them to deal with fires effectively. It has been observed that fuel contains oxidizing agents that combine with oxygen in presence of heat to produce fire. If the fuel gets exhausted or is removed from the process then the whole combustion process halts. (Houck & Siegel 2010). Oxygen combines with the oxidants in the fuel during combustion in presence of heat to produce fire. If oxygen supply is cut off there is eventual extinction of the fire. Heat is a major element in the fire triangle because it provides the energy necessary for the chemical reaction between oxygen and the fuel to produce fire. Heat may be removed from the triangle by use of water and leading to extinction of the fire.
The oxidation process refers to the chemical process during which an atom of a certain element loses some of its electrons to the atom or molecule of another element. During the oxidation process the atom losing the electrons becomes oxidized whereas the atom gaining the electrons becomes reduced. In biological terms oxidation refers to the addition of oxygen to a molecule or the molecule losing part or whole of a hydrogen atom. This can be denoted using the following chemical example, Fe2+____→Fe3+ +e-
The rate of oxidation is determined by various factors. This factors include the availability of a catalyst, the amount of oxygen available and the amount of temperature. A catalyst is a chemical substance that helps to speed up a certain chemical process. In instances where a catalyst is introduced to the oxidation process the rate by which it occurs is increased. Oxygen is a key element for oxidation to take place. Increased amount of oxygen supply increases the overall rate of the oxidation process whereas a deficiency in oxygen supply decreases the rate. High temperature increases the kinetic energy for both the accelerant and the oxygen molecules speeding up the rate oxidation takes place (Al, 2005)
Accelerants are highly exothermic fuels that vaporize easily and accelerate the burning process. In most cases accelerants comprise of ignitable liquids and arsonists use accelerants with the sole purpose of accelerating the speed of spread and the amount of damage caused by the fire started. There are various primary accelerators available for use by arsonists. These include gasoline, kerosene, paint thinner and diesel fuel. Kerosene is an accelerant that is used in many households in stoves and lamps as fuel. The combustion property of kerosene makes it highly explosive in most cases compared to other types of accelerants. Paint thinner is made up of petroleum components. This petroleum property of paint thinner aids it in dissolving with paint and handy when stripping paint on walls. Due to the petroleum property of paint thinner it is highly flammable and therefore a good accelerator. Gasoline is a petroleum product containing hydrocarbons which are main proponents of the oxidation process in fuels to accelerate a fire. Diesel fuel contains hydrocarbons too which are involved in the oxidation process and aid combustion at a high rate.
Accelerants contain hydrocarbons meaning they contain both hydrogen and carbon atoms. During combustion the hydrogen atoms react with oxygen to produce water. The carbon atoms react with oxygen and give off carbon dioxide which is a non-poisonous gas but is a pollutant in large amounts. Chemically this can be summarized by the following chemical formula CH4 + 2O2 --> CO2 +2 H2O. In some cases a mineral metal is present in the accelerant and after combustion has taken place the mineral residue remains.
Many cases of fires are reported all over the world daily. Investigators are tasked with the jurisdiction to perform forensic and extensive research on various cases to try and come up with the probable cause of the fire or rule out an arson attempt. There are several factors that investigators can take into consideration to paint a clear picture if an accelerant was used or not. Considering that most accelerants are liquids it is common that after successful extinction of the fire there will be some wetness left on the floor where the accelerant was not completely exhausted (Seferstein, 1998). Many accelerants have a certain odor although it is hard to identify an odor amidst clouds of smoke there still might be a hint of odor suggesting the use of an accelerant.
Normal fires burn in an upward movement damaging walls furniture and the roof not necessarily damaging the floor. In most cases where an accelerant is used there is notable damage on the floor where the accelerant was or where the fire was started. Accelerants have a petroleum property. Petroleum products do not mix with water which is the most common method of extinguishing fire. Considering this fact it is evident that after fire extinction there are rainbow colored sheens floating above water on the areas the accelerant was applied (International Association of Arson Investigators, 1992). Sometimes it is possible to note fire floating on water surface because accelerants float on water and thus combustion still goes on afloat the water underneath.
If the fire is put out early burn pattern on the lower part of doors and walls is notable if the accelerant was poured on the floor. In areas where the floor board are loose fire burns in a rundown pattern following the flow of the accelerant. It is also evident during accelerant propelled fires that fire burns directly off the floor or wall the accelerant was poured on. This fire produces large amounts of dark sooty smoke depending on the size of the fire and accelerant used. The most common observation to suggest the use of an accelerant would be the presence of fuel cans in the area.
With this is mind therefore it is possible to try and ascertain the cause of a certain fire to a great extent. It is also possible to collect evidence from the affected area and use it to clearly point out the specific accelerant used.
Al. A. (ED). (2005) Chemical physics of Pyrolysis, combustion and Oxidation. Berlin: Nova publishers. Print.
Houck. M & Siegel. J. (2010) Fundamentals of Forensic Science. Hardbound: Academic press. Print.
International Association of Arson Investigators (1992) A Pocket Guide to Accelerant Evidence Collection. Massachusetts: the association. Print.
Saferstein. R. Criminalistics (1998) an Introduction to Forensic Science. Upper Saddle River, NJ: Prentice Hall. Print.