Elements of Fire Investigation

Elements of Fire Investigation

Fire is the energy released when a chemical reaction occurs that involves the production of heat. According to chemistry, when a fire is produced, there must be combustion. Fire has several physical properties, which quantify it to be termed as so; it must be propelled by oxygen, combustible materials, or fuel, it should have a light, and there should be a flame or heat (What is fire? n.d.). Chemistry also emphasizes that fires have flames that comprise oxygen, nitrogen, water vapor, and carbon dioxide. Therefore, a fire occurs when combustion occurs, and its end products are heat, flames, and light, and there should be oxygen for it to occur.

For a fire to be combustible, there should be three elements that comprise the fire triangle. Ingredients of the fire triangle include heat or a source of ignition, fuel, and oxygen. Fire cannot be present if the mentioned elements of the triangle are inexistent. There must be a heat source for a fire to ignite, which should be sustainable for as long as the fire burns. The presence of heat as a fire burns gives it the power to spread fast through the elimination of moisture that may be present in fuel nearby (The Fire Triangle, n.d.). Therefore, through the presence of heat, a fire warms the air around it, giving it the strength to spread fast until it becomes ventilation-controlled or fuel-controlled. When a fire is ventilation controlled, it starts going off because of a lack of oxygen to ignite its further burning. As mentioned, oxygen is one of the three elements of the fire triangle that must be available for a fire to burn. Therefore, when there is a lack of oxygen, a fire will not burn, hence the term ventilation-controlled. Similarly, a fire can stop burning if it becomes fuel-controlled, implying that the fuel that was aiding its combustion burns out or is eliminated before the fire reaches it.

Sources of heat can include cigarettes, lightning, engine sparks, magnifying glass, and catalytic converters. Further, fire can be ignited if there is the presence of fuel sources, such as trees, shrubs, grass, decks, propane, or woodpiles. The fire’s intensity will always depend on the content of moisture present in the fuel that supports its burning. Additionally, the shape, size, quantity, and landscape arrangement of burning fuel plays a role in determining the intensity and severity of a fire. Several techniques can be used to put off a fire that has started burning and is proving destructive in nature. Firstly, a fire can be put out by cooling a material that is burning (Lyman, 2016). If cooling is applied, the heating element of the fire triangle is removed, meaning that the fire cannot burn anymore. Secondly, fire can be ended by removing its oxygen element, as in the ventilation-controlled scenario explained above. Thirdly, a fire can be put out by removing the presence of fuel, which is a mandatory element of the fire triangle for it to burn. Therefore, if there is no fuel, a fire will not burn as the mandatory triangle is incomplete. Overall, the chemical reaction involving the fire triangle elements must be broken for a fire to be put off.

Oxygen is a key element in the fire triangle that supports its burning through the oxidation process. If air is ambient, it will have 21% oxygen content, which is more than adequate to support combustion activities. Typically, there should be at least 16% of oxygen present in the air (What is fire? n.d.). Usually, the size of the flame produced in a fire depends on the percentage of oxygen available in the air. As such, if the size of the flame is small, then the percentage of oxygen present is low. The oxidation process occurs when oxygen combines with sources of heat and fuel to produce an end-product.  For a fire to be produced, oxygen atoms in the atmosphere combine with hydrogen and carbon to create water and carbon dioxide. The process releases energy and heat in the process and escalates if oxidation occurs quickly.

As such, if a fire is nearly suffocated and oxygen is added to it rapidly, then the air that was fanning the fire becomes re-oxygenated. The fire’s flames increase dangerously, which creates a backdraft or flashover. If a flashover occurs, the oxidation process has escalated, and a room that burned slowly becomes suddenly enveloped by flames from the ceiling to the floor areas because of thermal radiation. In a flashover, the temperatures often rise to beyond 1,000^oF rapidly, to the extent that any flammable content becomes consumed. Often, the area is termed as unsafe and untenable.

In contrast, in a backdraft, there should be the presence of a smoldering fire that becomes oxidized rapidly. If oxygen is added to the backdraft, a smoke explosion occurs because of the resultant heated gases that intensify the fire, increasing their inflammable ranges. If a flashover occurs in a forest or wild-land environment, it is termed a General Blaze Flash. Here, fire becomes oxidized, and if it was burning under low intensity, it becomes hotter and spreads even more to the point it destroys all vegetation in a GBF scenario.

Sometimes, a criminal starts a fire to destroy people’s property or for individual and mass murder purposes.  The above action is arson and has been characterized as challenging to examine because of several reasons. Firstly, the arsonist can ensure that their action is meticulously planned and executed using sophisticated tools that are difficult to trace (Schmalleger, 2016). Secondly, the arsonist can plan a malicious fire and start it even if they are not in the vicinity of the attack. Lastly, arsons are hard to detect because their perpetrators can easily use fire to wipe out any evidence that could prove that a fire was started on malicious grounds. When investigating arson, it is advisable to find chemicals at the scene of the crime that may have acted as accelerants. The investigator can then follow the path of the chemicals to reconstruct how the fire started and to determine the arsonist’s pattern.

Accordingly, the primary accelerants of fire include kerosene, gasoline, butane, turpentine, diesel fuel, and flammable solvents. Often, if an arsonist uses accelerants, there will be residues or soot that indicate petroleum products were used to start a fire for malicious reasons. The residues can then be examined to determine the arsonist’s pattern of starting a fire or its path as it burns. Arson investigation must always be centered on checking for a burn pattern. Most common arson signs include the presence of multiple ignition start sites, accelerant residue lying in a line, burning concentrated on the floor instead of the ceiling, and combustible liquid presence, even if on a small scale (Schmalleger, 2016).

Further, when investigating arson, it is advisable to check for the origins of soot, ash, or porous materials. The mentioned debris must be collected and then transported to laboratory sites in air-tight containers as they are proof of unburnt accelerants.  In some circumstances, fire vapor sniffers can be used to detect the presence of vapor accelerants that were used in arson. The fire intensity is an important aspect to investigate because fire does not burn with the same intensity in all circumstances. Some fires can burn with low intensity, and other times, they can burn with high intensity, depending on the type of accelerant used.

The gas chromatograph technique is the best way to determine if a collected residue or soot remains after a fire started by an arsonist is to test the collected residue. The method is sensitive, implying that it can detect the presence of accelerants quickly compared to normal eye observation. Additionally, using the gas chromatograph method of detecting the presence of accelerants is reliable to indicate an arsonist started a fire. Thus making it most viable to detect fires that burn maliciously (Dillon, n.d.). When using the gas chromatograph technique, the laboratory technician will often use a unique technique to separate the present hydrocarbons in a sample. Further, the laboratory technician will assign all the samples a unique pattern in a graphic manner, giving a general idea of the type of accelerant used to start a fire. Therefore, when testing collected soot or residue from a site where the fire is suspected to have been started by an arsonist, it is advisable to use the gas chromatograph observation method.

References

Dillon, S. R. (n.d.). Arson and investigation. Chemistry & Biochemistry – Department of Chemistry & Biochemistry. https://www.chem.fsu.edu/chemlab/chm1020c/Lecture%207/02.php

The fire triangle. (n.d.). University of South Carolina. https://www.sc.edu/ehs/training/Fire/01_triangle.htm

Lyman, M. D. (2016). Criminal investigation: The art and the science. Prentice Hall.

Schmalleger, F. (2016). Criminal justice today: An introductory text for the 21st century. Prentice Hall.

What is fire? (n.d.). Science Learning Hub. https://www.sciencelearn.org.nz/resources/747-what-is-fire

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You are the supervisor of a newly formed arson investigation unit. Although you have some personnel with basic crime scene training, you must start from the ground up to train them in elements of arson fire investigation. You start your training by handing out a white paper that will provide information to them about fire, fuel, and accelerants.

Elements of Fire Investigation

Address the following in 3–5 pages:
Describe what a fire is in terms of its physical properties.
Identify and explain the 3 elements that make up the fire triangle.
Explain the oxidation process.
How is the process affected by how fast the oxidation occurs?
What are the primary accelerants? Identify and describe them.
What do they leave behind chemically after they burn? Explain.
How can investigators search for and find trace elements of the accelerants?
What are they looking for at the scene that indicates accelerants were used?
Be sure to reference all sources using APA style.