MODULE I: ARSON
As we all know that fire can destroy houses and all possessions in less than an hour. Itcan reduce an entire forest to a pile of ash
and charred remains. Fire kills more people every year than any other force of nature. But on the other hand, fire is also helpful
in our daily life in many ways.
FIRE
Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various
reaction products. A state, process, or instance of combustion inwhich fuel or other material is ignited and combined with oxygen,
giving off light, heat, and flame. Fire is a chemical reaction that takes place when fuel, heat, and oxygen combine in an
uninhabited chain reaction.
CHEMISTRY OF FIRE
● Fire is uncontrolled combustion. It involves combustible materials which are foundaround us.
● It involves the oxidation of fuel and emits energy in terms of heat and radiation.Therefore, fuel, oxygen, and heat are
the three basic essential components to initiate fire.
Fire occurs whenever combustible fuel in the presence of oxygen at an extremely high temperature becomes gas. Flames are
the visual indicator of the heated gas. Fire can also occur from lower-temperature sources. Over time, combustible materials
such as smoldering embers can reach their ignition temperature. The fire triangle is a simple way of understanding
the elements of fire. The sides of the triangle represent the interdependent ingredients needed for fire: heat, fuel and oxygen.
Fire tetrahedron involves an additional component called chain reaction.
1. HEAT
A heat source is responsible for the initial ignition of fire, and is also needed to maintain the fire and enable it to spread.
Heat allows fire to spread by drying out and preheating nearby fuel and warming surrounding air.
Combustible materials may catch file at ignition temperatures. Heat is needed to start a fire. For many items found in the
home, the combustion temperature is 400 -600 degrees Fahrenheit. Some items may ignite more easily than others.
2. FUEL
This is anything that will-burn. Fuel must be available for ignition. It may be in the form of a solid, a flammable liquid or
gaseous state. Any chemical substance (solid, liquid or gas) used to start a fire or increase the intensity or speed is known as
fuel.
For example: When wood is heated, it pyrolyzes to form hydrogen, oxygen, ethane and methane gases, and methyl alcohol.
It is these highly flammable vapor which burn. Fuel in vapor form in its normal state, like natural gas, does not need to be
pyrolyzed. Most fuels are compounds of carbon, hydrogen, and oxygen along with traces of mineral matter.
Solids may be wood, cloth or paper. Examples of flammable liquids are kerosene, oil and gasoline. Vapors from paint, gasoline
and other flammable materials are considered gaseous.
Understanding that there were invisible, potentially dangerous vapors surrounding flammable chemicals is very important.
Natural gas and propane are other examples of flammable materials in a gaseous state.
Fuel is any kind of combustible material. It’s characterized by its moisture content, size, shape, quantity and the arrangement
in which it is spread over the landscape. Themoisture content determines how easily it will burn.
3. OXYGEN
• Air contains about 21 percent oxygen, and most fires require at least 16 percent oxygen content to burn.
, • Oxygen supports the chemical processes that occur during fire. When fuel burns, it reacts with oxygen from the surrounding
air, releasing heat and generating combustion products(gases, smoke, embers, etc.). This process is known as oxidation.
To stop burning of fire, out of the three elements present in fire triangle should be removed. Remove any one of the elements
and the fire goes out because you have stopped the continuing chemical reaction. Because only gases burn, solid and liquid fuels
must be heated until they become vapor before they can burn. Heat chemically decomposes a fuel into its gaseous elements. This
decomposition is known as pyrolysis.
Progress of Fire: The factors affecting the progress of fire are:
Availability of combustible material and oxygen
Temperature of fire
Humidity
Direction and velocity of wind
TYPE OF FIRE
The 5 main classes of fires are categorized by what caused the fire or what the fire uses as fuel,and are as follows:
• Class A: solid materials such as wood or paper, fabric, and some plastics
• Class B: liquids such as alcohol, ether, gasoline, or grease
• Class C: Flammable gases such as hydrogen, butane or methane.
• Class D: electrical failure from appliances, electronic equipment, and wiring
• Class E: metallic substances such as sodium, titanium, zirconium, or magnesiumClass F: grease or oil
fires specifically from cooking
1. CLASS A FIRE: ORDINARY FIRE
Class A fires are the most common of the 5 different classes of fires. They occur when common combustible materials like
wood, paper, fabric, trash, and light plastics catch fire. These accidental fires are ubiquitous across a variety of industries,
so it’s recommended to have adequate protection against “ordinary” fires in addition to other condition-specific fires.
As we all know that fire can destroy houses and all possessions in less than an hour. Itcan reduce an entire forest to a pile of ash
and charred remains. Fire kills more people every year than any other force of nature. But on the other hand, fire is also helpful
in our daily life in many ways.
FIRE
Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various
reaction products. A state, process, or instance of combustion inwhich fuel or other material is ignited and combined with oxygen,
giving off light, heat, and flame. Fire is a chemical reaction that takes place when fuel, heat, and oxygen combine in an
uninhabited chain reaction.
CHEMISTRY OF FIRE
● Fire is uncontrolled combustion. It involves combustible materials which are foundaround us.
● It involves the oxidation of fuel and emits energy in terms of heat and radiation.Therefore, fuel, oxygen, and heat are
the three basic essential components to initiate fire.
Fire occurs whenever combustible fuel in the presence of oxygen at an extremely high temperature becomes gas. Flames are
the visual indicator of the heated gas. Fire can also occur from lower-temperature sources. Over time, combustible materials
such as smoldering embers can reach their ignition temperature. The fire triangle is a simple way of understanding
the elements of fire. The sides of the triangle represent the interdependent ingredients needed for fire: heat, fuel and oxygen.
Fire tetrahedron involves an additional component called chain reaction.
1. HEAT
A heat source is responsible for the initial ignition of fire, and is also needed to maintain the fire and enable it to spread.
Heat allows fire to spread by drying out and preheating nearby fuel and warming surrounding air.
Combustible materials may catch file at ignition temperatures. Heat is needed to start a fire. For many items found in the
home, the combustion temperature is 400 -600 degrees Fahrenheit. Some items may ignite more easily than others.
2. FUEL
This is anything that will-burn. Fuel must be available for ignition. It may be in the form of a solid, a flammable liquid or
gaseous state. Any chemical substance (solid, liquid or gas) used to start a fire or increase the intensity or speed is known as
fuel.
For example: When wood is heated, it pyrolyzes to form hydrogen, oxygen, ethane and methane gases, and methyl alcohol.
It is these highly flammable vapor which burn. Fuel in vapor form in its normal state, like natural gas, does not need to be
pyrolyzed. Most fuels are compounds of carbon, hydrogen, and oxygen along with traces of mineral matter.
Solids may be wood, cloth or paper. Examples of flammable liquids are kerosene, oil and gasoline. Vapors from paint, gasoline
and other flammable materials are considered gaseous.
Understanding that there were invisible, potentially dangerous vapors surrounding flammable chemicals is very important.
Natural gas and propane are other examples of flammable materials in a gaseous state.
Fuel is any kind of combustible material. It’s characterized by its moisture content, size, shape, quantity and the arrangement
in which it is spread over the landscape. Themoisture content determines how easily it will burn.
3. OXYGEN
• Air contains about 21 percent oxygen, and most fires require at least 16 percent oxygen content to burn.
, • Oxygen supports the chemical processes that occur during fire. When fuel burns, it reacts with oxygen from the surrounding
air, releasing heat and generating combustion products(gases, smoke, embers, etc.). This process is known as oxidation.
To stop burning of fire, out of the three elements present in fire triangle should be removed. Remove any one of the elements
and the fire goes out because you have stopped the continuing chemical reaction. Because only gases burn, solid and liquid fuels
must be heated until they become vapor before they can burn. Heat chemically decomposes a fuel into its gaseous elements. This
decomposition is known as pyrolysis.
Progress of Fire: The factors affecting the progress of fire are:
Availability of combustible material and oxygen
Temperature of fire
Humidity
Direction and velocity of wind
TYPE OF FIRE
The 5 main classes of fires are categorized by what caused the fire or what the fire uses as fuel,and are as follows:
• Class A: solid materials such as wood or paper, fabric, and some plastics
• Class B: liquids such as alcohol, ether, gasoline, or grease
• Class C: Flammable gases such as hydrogen, butane or methane.
• Class D: electrical failure from appliances, electronic equipment, and wiring
• Class E: metallic substances such as sodium, titanium, zirconium, or magnesiumClass F: grease or oil
fires specifically from cooking
1. CLASS A FIRE: ORDINARY FIRE
Class A fires are the most common of the 5 different classes of fires. They occur when common combustible materials like
wood, paper, fabric, trash, and light plastics catch fire. These accidental fires are ubiquitous across a variety of industries,
so it’s recommended to have adequate protection against “ordinary” fires in addition to other condition-specific fires.
