Arson is a malicious fire. The arsonist tries to achieve:

  • Proper initiation      
  • Quick spread
  • Complete destruction

It is the crime of intentionally setting fire to buildings, vehicles or other property so as to cause damage. This also includes setting of fireside to others property or sometimes to have property so as to advantaged insurance facilities.

  • The lighting of fire side – It’s the essential element of arson, within the absence of fire lit, there’s no arson.
  • Intention or willfulness – This doesn’t includes fire caused by natural causes or accidents,
  • Malice – this doesn’t include fire i.e. intentionally set with positive intention and property.
  • The element of intent is critical to define a arson. People deliberately light fires for several reasons, including for few legitimate and legal purposes.
  • Fire follows the well-defined principles of burning. It produces heat, flame, smoke, and gases. The byproduct in combustion processes may or might not be seen readily. Flame includes open flame and smoldering glow. Smoke consists of very fine solid particles and condensed vapors. The composition of fireside gases emitted by the burning materials depends on the chemical makeup of the burning material, the quantity of oxygen available during burning, and therefore the temperature of the fire.
  • Most fire gases are highly toxic. They are the most important cause of fire deaths. This includes carbon monoxide gas not because it’s very toxic in nature but due to its abundance. When breathed in quantity, carbon monoxide gas causes unconsciousness and, eventually, death. At lower concentrations, it leads to disorientation and confusion and should cause other health hazards to victims. The second most dangerous gas produced by a fire place is CO2. While not toxic in itself, a 2 percent increase in CO2 within the air causes a 100 percent increase during a human’s breathing rate.
  •  Fire burns up and out. It leaves a V-shaped charred pattern on walls and vertical structures. A fire which is hot and fast at the purpose of origin will leave a pointy V pattern. While burning, if fire interacts with an obstruction, for instance a ceiling then it will burn across it and appearance for place to go up. Fire travels within the direction of air.

Motive of Arson

Few of the explanations for arson are given below:

  • Financial gain (Insurance Claim)
  • Vanity
  • Revenge
  • Civil Disorder
  • Crime Concealment
  • Delinquent Behaviour
  • Excitement
  • Pyromania
  • Dowry Death
  • Communal Purposes

Chemistry of Fire

 Fire may be a chemical reaction that takes place when fuel, heat, and oxygen combine in an uninhabited chain reaction. To stop burning of fireside, out of the three elements present in fire triangle should be removed. Remove anybody of the elements and therefore the fire goes out because you’ve got stopped the continuing reaction. Because only gases burn, solid and liquid fuels must be heated until they become vapour before they will burn. Heat chemically breaks down a fuel into its gaseous elements. This decomposition is known as pyrolysis.

For example: When wood is heated, it pyrolyzes to make hydrogen, oxygen, ethane and methane gases, and methanol, these are highly flammable vapours which burn. Fuel in vapour form in its normal state, like gas, does not need to be pyrolyzed. Most fuels are compounds of carbon, hydrogen, and oxygen alongside traces of mineral matter. When the fuels burn completely and freely in air, the carbon reacts with the oxygen, forming CO2, and therefore the hydrogen combines with the oxygen, forming water vapour.

The mineral matter remains behind as ash. As the oxygen within the fuel is employed up, oxygen is drawn from the air to continue the reaction. Mainly the fire spreads by transferring heat in 3 ways i.e. Radiation, Convection and Conduction.

Elements of Fire:

elements of fire, arson

Fuel: This is anything that will burn. Fuel must be available for ignition. It may be within the form of a solid, a flammable liquid or gaseous state. Solids may be wood, cloth or paper.  Familiar examples of flammable liquids would be kerosene, oil and gasoline. Vapours from paint, gasoline and other flammable materials are gaseous in nature. Understanding that there are invisible, potentially dangerous vapours surrounding flammable chemicals is very important. Natural gas and propane are other examples of flammable materials in a gaseous state.

Oxygen: This is needed for combustion. Fires use oxygen to maintain a state of combustion (burning). Fire produces smoke and poisonous gases.

Heat: Combustible materials may erupt at ignition temperatures. Heat is needed to start a fire. For many items found within the home, the combustion temperature is 400 – 600 degrees Fahrenheit.

Class of Fire

CLASS “A” FIRES: A category “A” fire can involve any material that features a burning ember or leaves an ash. Some examples of class “A” fires are wood, paper, or pulp. The adopted method for quenching fire of class “A” is to remove the heat. Water is considered to be most common agent, but other agents such as foam and dry chemical can be effectively used.

CLASS “B” FIRES: A class “B” fires involves flammable liquids or gases. Familiar examples would be gasoline, oil, propane and gas. A variety of fireside extinguishing agents is employed on flammable liquids fires employing all theories of fire extinguishment. Which agent is based to use is dependent upon the circumstances involved. Flammable liquid don’t ignite in their liquid state: rather it is a vapors being generated by these liquids that ignite. The mixture of oxygen and flammable vapors inn proper proportion needs only an ignition source to start the combustion process.

CLASS “C” FIRES: A category “C” fires involves live electrical equipment and need the utilization of an extinguishing agents and /or extinguisher which will not conduct electricity back to the fire fighters. Electricity is an energy source and an ignition source, but by itself won’t burn. Instead the live electrical equipment may function as a source of ignition for a category “A” fire like insulation and packaging, or a category ”B” fire.

CLASS”D” FIRES: A class”D” fires involves exotic metals such as sodium, zirconium, titanium and magnesium. These fires require special agents like dry powders and special application devices. The extinguishing agents and techniques used on “A”, “B”, “C” fire won’t work on fire “D”, nor are getting to be the agents used for fire “D” work on any other classes of fire. Many common agents like water will actually react to burning metal and increases the intensity of the heart during a violent manner.

CLASSIFICATIONFIRE RISKEXAMPLES
CLASS ASolid combustible materialsPaper, word, textiles etc
CLASS BFlammable liquidsGrease oil, paint, alcohol etc
CLASS CLive electrical equipmentOld wiring in walls, faulty appliances etc.
CLASS DExotic metalsSodium, magnesium etc.

Major Principles:

 1. Fuel, heat and oxygen are most important elements for combustion (burning).

2. Fuel must be ignited before it’ll burn.

 3. Without a reaction, fire will not burn materials such as wood, cloth and paper. Chain reactions are crucial to fires. If the reaction is interrupted, the fire will be altered or extinguished.

Three Phases of Combustion: The burning process occurs in clearly defined stages. For a fire fighter it is important to recognize different phases of fire so that he can understand the different levels of burning fires and to fight against it using different tools. These phases are classified on the basis of atmospheric conditions.

Incipient/Initial Phase (Growth Stage): This is the first phase; here fire produces water vapor, carbon dioxide, perhaps a small quantity of sulfur dioxide, carbon monoxide and other gases. Also in this phase the air oxygen content is reduced and produces fire. The fire may be producing a flame temperature well above 1,0000 F (5370C), yet the temperature in the room at this stage may be only slightly increased.

Free-Burning Phase (Fully Developed Stage): The second phase involves the all burning activities of the fire. In this phase, air rich in oxygen is strained into the flame and convection carries heat to the upper most regions. The gases heated up spreads out from the top downward, resulting in increased concentration of cooler air at low levels and results in the ignition of combustible material. Due to this heated air, firefighters are taught to keep low and use protective breathing equipment.

One breath of this super-heated air can burn the lungs. At this point, the temperature in the upper regions can exceed 1,3000 F (7000C). In the later stages of fire, it starts to progress and oxygen is continuously consumed by it and the point where there is insufficient oxygen to react with the fuel. The fire is then reduced to the smoldering phase and wishes only a supply of oxygen to burn rapidly or explode.

Smoldering phase (decay stage): Within the third phase, flame may cease to exist if the place of confinement is sufficiently airtight. Due to this, burning is reduced to glowing embers. The room becomes completely crammed with dense smoke and gases to the extent that it’s forced from all cracks under pressure. The fire will continue to smolder, and the room will completely fill with dense smoke and gases of combustion at the temperature of well over 1000 oF. 

The intense heat will have vaporized the lighter fuel fraction such as hydrogen and methane from the combustible material in the room. These fuel gases will be added to those produced by the fire and will further increase the hazards to the firefighters and create the possibility of a back draft.

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