Understanding APAR

Fire Theory

Fire is something that is very commonly known by humans since the beginning of civilization. But until now the definition of fire is still often debated. There are several definitions given by experts. The first is that fire is a rapid self-sustaining oxidation process accompanied by the evolution of heat and light in varying intensities. And can also be defined as the result of chemical mixing of heat, fuel and oxygen in the right proportions.

From these two definitions, it can be concluded that fire can only occur where there is combustible material (fuel), an ignition source (heat or thermal energy) and oxygen (oxidizing agent) from the air or from other sources. When these three elements are in concentrations that meet the requirements, an oxidation reaction occurs which is known as the combustion process.

Some of the heat will be absorbed by the material which then releases steam and gas which can alternately ignite and mix with oxygen in the air. This flame will continue as long as the three elements exist in a balanced concentration.

So, to create the initial fire three elements are needed:

1. fuel
2. heat
3. Oxygen (CO2)

When the temperature reaches the ignition point of a fuel, the element will produce fire, which combines to form a triangle which we know as the fire triangle and is described as follows:

Image of the Fire Triangle Theory

The definition of fire according to Dr. Tuve – also known as burning – contains three keywords; oxidation, self-sustaining and fast.

“Oxidation” is a chemical reaction in which two fuels (oxidizing and reducing agents) combine to form a product that is less effective than the ingredients themselves. Combustion is a particular type of oxidation reaction in which oxygen is the oxidizing agent, and the fuel is the reducing agent. Reductants or fuels are materials that contain the elements carbon and hydrogen.

The fire triangle theory was developed into the fire tetrahedron. It is suggested that in the combustion reaction radical substances are formed which cause a chain reaction.

Image of Fire Tetrahedron Theory

Fire Extinguishing Technique

The four elements in the fire tetrahedron must be present for fire to occur. These elements are heat, fuel, oxygen and chemical reaction chains. Although not everyone generally knows about the combustion process, it is generally accepted that fire is a chemical reaction. This reaction relies on the substance rapidly oxidizing, or combining with oxygen very quickly to produce heat and fire.

From this concept, fire suppression can be done in four ways, namely:

1. By removing heat

In order to remove heat, what can be done is to use materials that absorb heat or act as heat exchangers. Water is not the only agent used to achieve this, but it is the most common.

2. By removing fuel

In many circumstances, it is not easy to try to remove fuel from a fire. When dealing with flammable liquids, the valve can be turned off and the storage vessel pumped to a safe area to help remove the fuel supply from the fire. Flammable gas will be completely extinguished by turning off the fuel supply.

3. By removing oxygen

Oxygen as present in our atmosphere (21%) is sufficient to support combustion in most fire situations. Removal of air or oxygen can be achieved by separating it from the fuel source or by displacing it with an inert gas. One example is using suds in flammable liquid fires, wet blankets, or covering fire pans tightly. Agents such as CO2, nitrogen, and steam are used to replace oxygen.

4. Interrupt the chain of chemical reactions

Modern fire extinguishers use chemicals such as dry chemicals and halons, which have been proven effective for extinguishing a variety of fires, although they do not remove heat, fuel, or oxygen. Dry chemical powders and halons are thought to suspend or bind to free radicals produced in the combustion process and thereby prevent them from continuing chemical chain reactions.

APAR theory

APAR according to PERMEN No. 4 of 1980 is a tool that is light and easy to operate by one person to extinguish a fire when a fire occurs

Types of Light Fire Extinguisher:

1. Water

The nature of water in extinguishing fires is that it physically takes heat (cooling) and is very appropriate for extinguishing solid materials (class A).

2. Foam

Foam is used to extinguish class A and B fires

Foam extinguishes fire through a combination of three extinguishing actions namely covering, weakening and cooling.

• Covering means creating a foam blanket over the burning material, so that contact with oxygen (air) is lost
• Attenuating is  preventing  evaporation  of  liquids  which  are  flammable
• Cooling that is absorbing calories fluid which is flammable so the temperature drops

3. Dry chemical powder

• Ammonium hydro phosphate can be used to extinguish class A, B and C fires
• Sodium bicarbonate can be used to extinguish class B and C fires
• Calcium bicarbonate can be used to extinguish class B and C fires

4. Carbon dioxide (CO2)

• CO2 fire extinguishing media is in the form of a high pressure liquid phase
• The working principle of CO2 is a reaction with O2 so that the concentration decreases from 21% to the same or less than 14%. This is called blackout by shutting down.
• CO2 extinguishing media is not toxic but can stun people or die from lack of oxygen
• The weakness of CO2 is that it cannot prevent re-fires after the fire is extinguished (reignitation) because CO2 cannot bind O2 continuously but can bind O2 in proportion to the amount of CO2 available while the supply of oxygen around the fire area continues.

5. Halons

• When exposed to the heat of a fire at a temperature of around 485oC, halon gas will undergo a decomposition process
• The substances produced from the decomposition process will bind hydrogen and oxygen (O2) elements from the air. Because the nature of the new substance is toxic, it is quite dangerous for humans.
• When a fire occurs, if halon is used to extinguish the fire, all occupants must leave the room except for those who already know how to use it.
• The types of halon gas that can be used as extinguishers are halon 1301 (BTM) and halon 1211 (BCF).
• Halon 1301 (BTM – CBrF3) with a concentration of 4% is used to prevent fires in electronic equipment.

Construction Type of Light Fire Extinguisher:

1. Fixed Pressure Tube Type(Stored Pressure Type) is a fire extinguisher whose extinguishing agent is pushed out by dry gas without active chemicals/dry air which is stored together with the extinguishing powder under pressure. Generally this type of tube is used for fire extinguishers with foam, water and DC contents
2. Gas Cylinder Type (Gas Cartridge Type) is a fire extinguisher whose extinguishing agent is pushed out by pressurized gas released from the gas cylinder. Generally this type of tube is used for fire extinguishers with foam, water, DC, CO2 contents

Location of Light Fire Extinguisher Placement:

1. The maximum distance between APARs is 15 m
2. Place the fire extinguisher outdoors using a box
3. The maximum installation height of APAR is 1.2 m from the bottom of the floor, except that CO2 and Dry Chemical can be placed lower provided they are >15cm
4. Mark the APAR with a height of 125 cm from the bottom of the floor directly above the APAR.
5. Fire extinguishers are installed in places that are easy to see, reach and easy to use.
6. Cupboards or boxes can be locked provided that the front is provided with safety glass with a maximum thickness of 2 mm.

Source : https://www.academia.edu/19569123/APAR