types of Fire
According to the characteristics of combustion, different types of fires are determined, which can be grouped as follows:
1 ° Class A Fire
2 ° Class B Fire
3 ° Class C Fire
4 ° Class D Fire
These are the fires that involve solid organic materials, in which embers can be formed, for example, wood, paper, cardboard, straw, coals, textiles, etc. It has been standardized as a symbol to be used a triangle with a green background inside which the letter A is placed.
These are fires that involve flammable liquids and solids that are easily melted by heat (liquefiable solids). Within this item we can find all the hydrocarbons, alcohols, paraffin, wax, etc. It has been normalized as a symbol to use a red square inside which the letter B is placed.
These are the fires that involve energized electrical equipment, such as electrical appliances, switches, fuse boxes and power tools, etc. It is symbolized by a blue colored circle inside which is placed the letter C.
They are deflagrating fires, in alkaline and alkaline earth metals, as well as metallic powders; they combust violently and generally with very intense flame, they emit a strong caloric radiation and they develop very high temperatures. On this type of fires you should NOT use water, as this would react violently. Magnesium, sodium, potassium, titanium, zirconium, aluminum powder, etc. are found within this type of fires.
It is symbolized by a five-pointed star with a yellow background inside which the letter D is placed.
after having observed great difficulty in extinguishing fires in industrial fryers, this particular classification was made for this type of fires. It was called then Fire K (by the initial of the word Kitchen).
Extinguishers and Fire Extinguishing Agents.
To better understand the action of extinguishing agents , and to classify them, we must first analyze what extinction is, and classify them according to their types.
We said before that fire is a combustion. But is fire synonymous with "flames"? Can there be fire without flames? The answer is positive, and in a broader sense to which we commonly give the word fire as synonymous with "llamas", we can classify the fires as:
Surface or rooting fires (without flame)
They are fires in solid substances. The combustion is superficial and progresses towards the central core of the burning mass. Examples of combustion without flames are: pure carbon and other easily oxidizable non-metals, such as sulfur and phosphorus, as well as easily oxidizable metals (magnesium, aluminum, zirconium, uranium, sodium, potassium, etc.). They usually develop high combustion temperatures of between 2500 and 3500 ° C.
They are direct evidence of the combustion of gases or vapors from flammable liquids
According to this classification of the fires, we can say that:
- in a SOLID there is fire of SURFACE AND FLAME
-In a LIQUID there is a FLAME fire
-In a GAS there is a FLAME fire
Fuels can occur in any state of aggregation: solid, liquid or gaseous.
Why can there be a flame fire in a solid, in addition to rooting fire? Because what burns in the fire of flames, always, are the vapors and gases that the fuel releases in the process of combustion.
And a solid, like any liquid, can release vapors according to the temperature it is in. Depending on the fuel, a solid, a liquid or a gas, different extinction methods are used:
1 ° The solid fuels normally have a mass combustion, raising the temperature of the same over the entire surface. The main and classic extinction technique is to cool the incandescent mass.
2 ° In liquid fuels, the fundamental and classical technique of extinction is to cover the liquid mirror avoiding the transfer of heat and the free generation of steam (which is what produces the flames)
3 ° The substances in gaseous state, burn in all its mass, producing in many cases, explosion risks. The classic techniques of extinction are to saturate them with inert material or to avoid their contact with heat sources.
In all cases, modern extinction techniques combine physical methods with chemicals, and fire extinguishers must be chosen based on fuel. We can say then that there are two types of extinction:
Physics and chemistry.
Remembering the Triangle of Fire, we understand why physical extinction consists of three fundamental methods: Elimination of fuel, suffocation and cooling.
Remembering the Fire Tetrahedron, this method is based on the interruption of the chain reaction. The free radicals that the fuel generates and that are the elements that combine with the oxygen in the oxide-reduction process, compete with the extinguishing agent which is akin to these radicals, capturing them and inhibiting their action.
Type and classification of Fire Extinguishing Agents
The different types of extinguishing agents, can be classified as physical or chemical according to the type of effect it has on combustion. If the main effect of the agent is a physical effect, acting on the triangle of fire, we will say that the agent is physical; in an analogous way, if the main effect is the chemical effect, acting on the tetrahedron of fire, we will say that the agent is chemical. In this way, we have assembled the following table according to the most common types and types of extinguishing agents.
Type and classification of fire extinguishers.
The fire extinguishers are portable elements destined to the fight against incipient fires, or principles of fires, which can be dominated and extinguished in brief form.
According to the extinguishing agent extinguishers are divided into the following types:
- Water based
- Foam based
- Based on carbon dioxide
- Powder based
- Based on halogenated compounds
- Based on halogen replacement compounds
We will list below the most common extinguishers, and classify them according to the fire class for which they are suitable:
Water is a physical agent that acts mainly by cooling, by the great power of absorption of heat that it possesses, and secondarily acts by suffocation, because the water that evaporates at the high temperatures of combustion, expands its volume by approximately 1671 times , displacing oxygen and combustion vapors. They are suitable for class A fires. They should not be used under any circumstances in Class C fires, as the running water with which these extinguishers are charged conducts the electricity.
Foam extinguishers (AFFF).
They act by cooling and suffocation, because the foam generates a continuous layer of aqueous material that displaces the air, cools and prevents the escape of steam in order to stop or prevent combustion. While there are different types of foams, the most common extinguishers use AFFF, which is suitable for hydrocarbons. These extinguishers are suitable for Class A fires and class B fires.
Because this gas is enclosed in pressure inside the extinguishers, when it is discharged it expands abruptly. As a result of this, the temperature of the agent drops drastically, to values that are around -79 ° C, which causes it to become dry ice, hence the name that receives this discharge of "carbon dioxide". This fog when coming into contact with the fuel cools it down. There is also a side effect of suffocation due to displacement of oxygen. It is used in class B and class C fires, as it is not conducive to electricity. In fires of class A, it can be used if it is complemented with a water extinguisher, because by itself it does not manage to extinguish the rooting fire. In combustible liquids must be careful in their application, in order to avoid splashing.
Dry chemical extinguishers triclase ABC.
They act mainly chemically by interrupting the chain reaction. They also act by suffocation, since the monoammonium phosphate of which they are generally composed, melts at the temperatures of combustion, originating a sticky substance that adheres to the surface of the solids, creating a barrier between these and oxygen. They are suitable for class A, B and C fires.
Extinguishers based on replacements of halogens (Haloclean and Halotron I).
They act mainly, like chemical dust, chemically interrupting the chain reaction. They have the advantage of being clean agents, that is, they do not leave traces or residues, besides being conductors of electricity. They are suitable for class A, B and C fires.
Fire extinguishers based on special powders for class D.
Some metals react violently if the wrong extinguishing agent is applied. There is a wide variety of formulations to fight the fires of combustible metals or metal alloys. There is no universal extinguishing agent for combustible metals, each dry powder compound is effective on certain metals and specific alloys. They act in general by suffocation, generating when applying a crust that acts as a barrier between metal and air. Some also absorb heat, acting therefore by cooling at the same time as by suffocation. They are only suitable for the fires of class D.
Fire extinguishers based on water spray.
The main difference as common water extinguishers, is that they have a special discharge nozzle, which produces the discharge of water in fine drops (fog), and also have distilled water. All this, makes them suitable for class C fires, since this discharge does not conduct electricity. They are also more effective than common water extinguishers, by vaporizing the fine drops on the surface of the fuel, which generate greater heat absorption and a greater suffocation effect (remember that the water vaporized expands by approximately 1671 times , displacing oxygen). They are suitable for class A and C fires.
Fire extinguishers for class K fires based on potassium acetate.
They are used in fires that are produced on oils and fats from industrial fryers, kitchens, etc. The potassium acetate is discharged in the form of a fine mist, which upon contact with the surface of the oil or grease, reacts with this producing a saponification effect, which is nothing more than the formation of a soapy foam that seals the surface separating it from the air. This fog also has a cooling effect of oil or grease, as part of these fine droplets vaporize causing the temperature of the oil or fat to fall.
Remove it from its support.
Go to the place where the focus is WALKING.
Position yourself in favor of the wind if it is outside or in favor of drafts if it is inside an office or room.
Remove the safety ring located at a distance of 1.50 meters.
With one hand take the discharge valve and with the other, the hose.
Press the pressure handle pointing to the base of the fire
Squeeze the discharge valve by directing the jet of extinguishing agent to the base of the flame if it is class "A" fire, sweep from one end to the other if it is class "B" fire.
Use the necessary charge to put out the flames.
Once the fire has been extinguished, withdraw from the place by REVERSING, since the fire may reappear. Advise who it is to send immediately to RECHARGE the equipment used.
Do not place the extinguisher on the floor. It must be placed at a minimum height of 1.30 meters above the floor.
It should be placed in a red rectangle and in plain sight.
Remember: The best way to operate an fire extinguisher is to prevent the fire from starting by complying with Fire Prevention regulations.
Fight against fire.
The professionalized training of personnel involved in prevention and extinction is a priority objective of the Public Administrations and Private Companies responsible for the protection of forest cover against fire.
The fight against fires requires having a specialized staff that performs with the greatest efficiency and at the same time with the maximum security against possible accidents, the tasks of surveillance and extinction that this activity includes.