Fire Classification - Know How to Handle It

What is fire?

jungle fire

We have all seen a building or a plant burning in flames. We all understand what fire is? We know that fire is another name given for combustion. Combustion, or "fire" is a process that occurs when oxygen and heat combine in a reaction in the presence of fuels. When this reaction occurs very quickly, combustion takes place, and in it, the fuel begins to dry out and burns producing flames.

Class of Fire, Fuel & extinguishing agent

Class of fire, fuel and extinguishing agent
Class	Fuel	Extinguishing Agent
A	Ordinary combustible material such as wood, cloth, paper etc.	Water type, CO2, DCP
B	Flammable liquid and gas such as grease, gasoline, hydrocarbon	Foam, CO2, DCP
C	Electrical fire	CO2, DCP
D	Combustible metal such as sodium, magnesium, pyrophoric substances etc.	Sodium chloride (MET-L-X)

What is the Fire Tetrahedron?

Four elements must be present, and besides, in the proper proportion. These four elements are

HEAT

OXYGEN

FUEL AND

CHAIN REACTION

Fire Principle:-

TetrahedronThree elements (fuel, heat and oxygen) are called the fire triangle. If these three elements, or any of them, are not in the proper quantity, there will be no combustion. For example where you visit this page, but there is no combustion or fire. Why? Because the fire triangle is not in the proper balance or some of these elements have been combined, the third is not present. But, of course, when all three are present, and in the correct proportion then start chain chemical reaction and fire appears, and this fire can burn rapidly with great flames,

Heat

What is heat? Heat is a form of energy and energy is molecules in motion. This molecular activity is measured by the temperature that is expressed in degrees centigrade. When the fuel reaches a certain temperature, it begins to "break down", releasing molecules in the form of gases, first water vapour and then others, which are highly flammable. This temperature is called the "vaporization point" of the fuel. The “ignition temperature” of a fuel is the temperature at which these gases will ignite and cause combustion to continue even after the source of external heat, such as a match or lighter, is removed.  

Oxygen

Oxygen is one of the elements that are part of our atmosphere, in a volume of 21%. It is chemically combined with fuel.

Fuel

A fire does not exist if there is no material to burn, for now, we must remember that the fuel does not burn without the presence of heat and oxygen in the correct proportion.

Chemical Chain Reaction

There is no longer fire if the fire triangle (fuel, heat and oxygen) fail to maintain the Chemical Chain Reaction. Simple no reaction no fire, we use a DCP fire extinguisher to stop the chemical chain reaction

What are the three heat transfer (spread) phenomenon

Sometimes oxygen is consumed so rapidly at the base of the fire that its proportion decreases, and the fire is soon out of balance, although there is still enough heat and steam left. As the hot gases rise into the air, they become saturated with oxygen again, and flames may appear in the plume of smoke far above the fire. The oxygen supply for combustion depends on the ability of the air to circulate freely between the fuels. But heat must also be able to reach the fuel and raise its temperature to ignition. How does this process happen? There are 3 forms of heat transmission: -

RADIATION - CONDUCTION - CONVECTION

Radiation

Radiation is the transfer of heat energy through space, by medium waves, such as energy heat that the earth receives from the rays of the sun. When we're sitting close to a fire we get warmed by the heat, it is even possible severe heat burns, simply being too close to the fire without needing to touch the flames, we heated by radiation, but as we move away it decreases,

Conduction

Conduction is the transfer of heat energy through a substance by direct molecular action, that is, it passes from a molecule to those that have next to her, and so on

Convection

Hot gases rise. This method of heat transmission is called convection. When hot air rises, the cold air will fill the vacuum left by the ascending hot air. It can be seen that if we place a paper on top of a flame without touch, it heats up to its ignition temperature and begins to burn.

If another paper is placed next to the flame, it burns more difficult or does not burn. This is because it only receives heat from radiation, and it does not burn because it does not receive enough heat to raise its temperature to that of ignition. So, fuels on a slope above the fire are heated by convection.

When this occurs the hot air that it rises, drags cold air, and with it, a new supply of oxygen is absorbed by the base of the fire.

What are the three Fire Extinguishing Method?

Cooling - Applying water to reduce temperature or observe heat

Smothering - Applying such as CO2 to remove  oxygen

Starvation - Removal of fuel

A common cause of fires in the workplace,

• Electrical equipment,

• Deliberate ignition,

• Hot work,

• Smoking,

• Heating Appliance,

• Unsafe use of flammable material,

• Chemical reaction,

• Mechanical heat

• A safe system of work

Use of electrical equipment in flammable atmospheres,

Hazardous area classification

Zone 0 - the explosive atmosphere is present continuously or frequent

Zone 1 - the explosive atmosphere likely to occur in normal operation,

Zone 2 - the explosive atmosphere not likely to occur in normal operation,

Easy on fire protection and prevention

• Keep/maintain good housekeeping

• Smocking in the only designated area

• Limit source of ignition 

• Know the location of the fire extinguisher and manual call point

• Regularly inspection of electrical wiring and insulation

• Know the PASS (P - pull the pin, A - aim the nozzle at the firebase, S - squeeze the lever, S - sweep from side to side) system to operate the fire extinguisher.