Environmental Chemistry

Fire Extinguisher

Fire is one of the most natural phenomena we use in our everyday lives to perform different activities. For example; cooking, lighting and various other activities. All this is due to the controlled production of fire. The fire is a blessing to us can become dangerous within seconds if it is not in a controlled manner. The most common examples of this are the forest fires which cause damage to most of the forest, animals living there and our natural resources. Another good example of fire damages is the fire that breaks out in houses, causing a lot of damage. In those situations, we usually call the fire department to monitor the fires. Fire authorities use fire extinguisher to extinguish the fire, depending on the intensity and magnitude.

According to the principle of the fire triangle, for the production of fire, we need three elements to be present, they are fuel (something that can burn), a source of heat (which can combust the fuel), and air (for a constant supply of oxygen).

Fire Extinguisher

                                                                                                Fire Extinguisher

What is a Fire Extinguisher?

A fire extinguisher is an external fire safety system useful to extinguish or control minor fires, often in emergency cases. It is not for use in an out-of-control fire, such as where the fire has reached the ceilings, endangering the customer (i.e., no escape route, smoke, explosion hazard, etc.) or otherwise requires the skills of a fire brigade. Usually, a fire extinguisher consists of a hand-held cylindrical pressure vessel carrying an agent which discharges to extinguish the fire. Fire extinguishers produced with non-cylindrical pressure vessels do exist but are less common.

There are two different types of fire extinguishers: cartridge-operated and stored-pressure. In the stored pressure units, the expellant is in the same chamber as the firefighting agent. Various propellers are used, depending on the agent used. Usually, water and foam extinguishers utilize air. Stored-Pressure fire extinguishers are the most common form of fire extinguishers. Cartridge-operated extinguishers carry the extinguishing gas in a different cartridge. It is punctured before the discharge, exposing the propellant to the extinguishing agent. This kind of fire extinguishers is not as common, used mainly in places like industrial facilities, where the usage is higher than the average.

Fire extinguishers further categorize into Hand-held and Cart-mounted (also called wheeled extinguishers). Hand-held extinguishers weigh from 0.5 to 14 kgs and are thus easy to carry by hand. Cart-mounted units typically weigh more than 23 kgs. These wheeled extinguisher models are most common at airport runways, building sites, heliports, docks and marinas.

Types and Classes of Fire Extinguishers

There are five different kinds of fire extinguishers, including wet chemical, CO2, dry powder, foam and water. The requirement for different types of fire extinguishers comes from the different kinds of fuel that can cause a fire.

The various kinds of fires caused by the various types of fuels categorize into different classes fires.

Classes of Fires

There are six different types of fire classes

Class A Fire Class A fires involve fires caused by fuel materials, including paper, cloth, wood and other flammable solids.

Class B Fire: Class B fires involve fires triggered by flammable liquids, such as paint, turpentine and petrol, among several others.

Class C Fire: Class C fires involve fires ignited by flammable gases, including methane, butane or hydrogen, among several others.

Class D Fire: Class D fires involve fires by combustible metals including potassium, aluminium or magnesium, among several others.

Class F Fire: Class F fires involve those caused by cooking oils, such as a chip pan fire.

Electrical fire: Electric fires apply to the type of fires involving electrical equipment, but after the removal of electrical appliances, the type of fires is changed.

Types of Fire Extinguishers

Foam Extinguishers

 Foam Extinguishers are the most common form of fire extinguishers useful for class B fires. However, they are water-based, which means that they are also useful in extinguishing class A fires.

These fire extinguishers are for fires caused by various organic materials, like woods, cardboard, coal, textiles and paper, and flammable liquids, including petrol and paint. This type of fire extinguishers is not useful for fires caused by flammable metals, kitchen fires and fires involving electrical appliances.

Water Extinguishers

 Water Extinguishers; Work as same as foam extinguishers. These are useful for class A fires. Water Extinguishers are also used for fires caused by various organic materials, like woods, cardboard and paper. It is also not useful for fires caused by flammable metals, kitchen fires and fires involving electrical appliances.

Dry Powder Extinguishers

 Generic dry powder extinguishers are also known as ABC extinguishers. These can be useful for class A, class B and class C fires. They are not for use in confined spaces as the dry powder in the extinguisher can be inhaled. Often, it’s not easy to clean up the residue after the fire. They can also be useful for fires involving electrical appliances.

Along with fires caused by various organic materials, like woods, textiles and paper, and flammable liquids, including petrol and paint, any fire involving electrical equipment up to 1000 V can extinguish with the aid of this fire extinguisher.

Wet Chemical Extinguishers

 Wet chemical extinguishers are for use in Class F fires, like cooking oils and fats. They are also useful in Class A fires, but it is more common to use a foam or water extinguisher for this fire hazard.

Carbon Dioxide (CO2) Extinguishers

Carbon Dioxide (CO2) Extinguishers are primarily in use for electrical fire hazards and are typically the primary type of fire extinguisher in data server rooms. They put out Class B fires, too. CO2 extinguishers suffocate fires by displacing the oxygen that the fire needs to burn.

Working of Water Fire Extinguishers

As the fire brigade begins to spray water over the areas where the fire occurred, the water cools off the fire temperature. The ignition temperature of the fuel decreases due to the continuous water spraying. So fuel can no longer burn, so it stops the fire from spreading. In addition, water vapours block the oxygen supply on the fuel surface, thus reducing the supply of oxygen to the fuel surface.

FAQs about Fire Extinguisher

Q.1. In which places do we find fire extinguishers?

Answer. We can find fire extinguishers in public places and private places like museum, hospitals, construction sites, airport runaways, schools, laboratories, heliports, docks and marinas, etc.

Q.2. What is a fire triangle?

Answer. A fire triangle is a principle that explains the elements necessary for a fire to start, they are;

  • Fuel – for combustion.
  • Air – Constant supply of oxygen for letting the fire burn.
  • Heat – To provide ignition temperature.

Q.3. What are the different colours that help identify fire extinguishers?

Answer. The colour of the fire extinguishers classify based on the agents they contain, such as;

  • Foam extinguishers: The label colouring for this type of extinguisher is cream.
  • Water extinguishers: The label colour for this type of fire extinguisher is bright red.
  • Dry powder extinguishers: The label colouring for this type of fire extinguisher is blue.
  • Wet chemical extinguishers: The label colour for this type of fire extinguisher is yellow.
  • Carbon dioxide extinguishers: This type of extinguisher has a black label on it.
Share with friends

Customize your course in 30 seconds

Which class are you in?
Get ready for all-new Live Classes!
Now learn Live with India's best teachers. Join courses with the best schedule and enjoy fun and interactive classes.
Ashhar Firdausi
IIT Roorkee
Dr. Nazma Shaik
Gaurav Tiwari
Get Started

One response to “Urea”

Leave a Reply

Your email address will not be published. Required fields are marked *

Download the App

Watch lectures, practise questions and take tests on the go.

Customize your course in 30 seconds

No thanks.