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Fire extinguishers are essential safety devices designed to combat different types of fires and play a critical role in fire prevention and control. There are mainly five types of fire extinguishers. Understanding the various types of fire extinguishers and how they work is fundamental for effective fire safety measures. These devices are engineered to address specific fire classes, employing distinct methods to suppress or extinguish fires.
This discussion shall explain the types of fire extinguishers and their uses. This topic in mechanical engineering is important for your upcoming examinations like SSC JE ME and RRB JE Mechanical Engineering.
A fire extinguisher is a device designed to suppress or extinguish fires caused by explosive materials, gas leaks, or electrical faults, and it comes in various variants tailored to specific fire zones and fire classes. It serves the purpose of quelling or altering fires effectively.
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When fire brigade personnel initiate the application of water to areas affected by fire, the water serves to reduce the fire's temperature. Through a continuous spray of water, the temperature gradually decreases until it falls below the ignition point of the fuel. Consequently, the fuel becomes incapable of igniting, effectively halting the fire's progression. Additionally, the water vapour generated during this process obstructs the oxygen supply to the fuel surface, thereby diminishing its access to oxygen.
However, it's important to note that water fire extinguishers are not suitable for all fire scenarios. For instance, in cases involving electrical fires or fires caused by inflammable substances, alternatives such as soda-acid or Carbon fire extinguishers are typically employed. These alternatives function by disrupting the oxygen supply to extinguish the fire.
Fire extinguishers are safety devices that are used to extinguish small fires during emergencies. They are classified based on the nature of fire they are designed to combat. It is important to understand the types of extinguishers to ensure proper usage and maximum effectiveness. Each type is colour-coded and labelled for quick identification. Choosing the right Fire extinguishers is important for safe and effective fire control.
Water-type fire extinguishers utilise water to suppress fires by cooling the burning material below its ignition point. When water is sprayed or directed at the source of combustion, it reduces the temperature of the combustible substance, effectively extinguishing the fire. However, these extinguishers have limitations; they are not suitable for oil or petrol fires due to density differences, as water can't effectively penetrate the surface. Moreover, using them on electrical fires poses risks of electric shock due to water's conductive properties.
Foam-type fire extinguishers work by restricting the supply of oxygen to the burning material. They consist of a cylinder containing an Aluminium Sulphate Solution and another cylinder with a sodium bicarbonate solution saturated with saponin to produce foam. When activated, these components mix to create foam, which covers the combustible material, cutting off the oxygen supply and extinguishing the fire. These extinguishers are ideal for combating petrol and oil fires.
Carbon dioxide fire extinguishers use pure \(CO_2\) to suppress fires by spraying it onto the combustible substance. These extinguishers typically do not have pressure gauges, and the filling of cylinders is verified using weighing methods.
Dry powder fire extinguishers employ mono ammonium sulphate powder to extinguish fires, particularly those involving metal combustible materials.
Wet chemical fire extinguishers are specifically designed for commercial kitchens and cooking areas. They use a solution of potassium acetate to smother fires caused by cooking oils and fats. This solution not only extinguishes the fire but also cools down the burning surface to prevent re-ignition. Equipped with a discharge hose, these extinguishers allow operators to direct the agent accurately onto the fire source. Regular maintenance is crucial to ensure their readiness in commercial kitchen fire emergencies.
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There are five primary types of fire extinguishers: water, foam, \(CO_2\), powder, and wet chemicals, each designed for specific fire classes. Selecting the appropriate fire extinguisher is crucial to meet your specific firefighting requirements. The various classes of Fire Extinguishers are:
Class |
Type |
Class A |
Solid Combustibles |
Class B |
Flammable Liquids |
Class C |
Flammable Gases |
Class D |
Flammable Metals |
Electrical |
Electricals |
Class F |
Cooking Oil |
Fire extinguisher is classified as mainly in five main categories as on their use. Each type of fire extinguisher is used for a particular class of fire. Water extinguishers are ideal for class A fires, which involve wood or paper. Foam extinguishers are used for class A & B. CO₂ extinguishers are clean and residue-free, best for electrical and flammable liquid fires. Wet chemical extinguishers specialise in Class K/F fires, such as kitchen oil blazes. Choosing the fire extinguisher according to the class of fire is very important. Aspirits can check a detailed comparison of the 5 types of fire extinguishers below.
Type of Extinguisher |
Suitable Fire Classes |
Extinguishing Agent |
Applications |
Advantages |
Limitations |
Water |
Class A (Solid combustibles) |
Water |
Paper, wood, textiles, cardboard |
Easy to use, low cost, widely available |
Not suitable for electrical or flammable liquid fires; risk of electric shock |
Foam (AFFF) |
Class A & B |
Aqueous Film Forming Foam |
Petrol stations, garages, warehouses |
Forms a barrier to prevent re-ignition, good for liquid fires |
Not suitable for Class C (gas) or electrical fires |
Dry Powder (ABC) |
Class A, B, C & Electrical |
Dry chemical powder (monoammonium phosphate or ABC powder) |
Industrial settings, mixed risk areas |
Versatile; safe on electrical fires |
Leaves residue; may damage sensitive equipment |
Carbon Dioxide (CO₂) |
Class B & Electrical |
Compressed CO₂ gas |
Electrical panels, server rooms, labs |
No residue, safe for electronics |
Limited range, risk of re-ignition, suffocation in enclosed spaces |
Wet Chemical |
Class F (K in US) |
Potassium acetate or citrate solution |
Commercial kitchens, deep fat fryers, and restaurants |
Cools and saponifies fats/oils, prevents re-ignition |
Limited to cooking oil/fat fires; not suitable for general-purpose use |
The PASS technique is very effective for using the fire extinguisher safely. It ensures that even a non-trained person can respond quickly in a time of fire emergency. It is advisable to always maintain a safe distance from fire and be prepared if fire reignites. For more details, candidates can refer to the table provided below.
Step |
Action |
P – Pull the Pin |
Hold the extinguisher upright and pull the safety pin to break the tamper seal and unlock the lever. |
A – Aim the Nozzle |
Aim the nozzle or hose at the base of the fire, not the flames, to target the fire source. |
S – Squeeze the Handle |
Firmly squeeze the handle to release the extinguishing agent in a steady, controlled manner. |
S – Sweep Side to Side |
Sweep the nozzle side to side across the fire until it is completely out or the extinguisher empties. |
The various uses of fire extinguishers are:
It is important to inspect and do maintenance of fire extinguishers to ensure safety. Neglecting any safety precautions with these devices can lead to failure when they are required the most. It is advisable to do a monthly inspection of fire extinguishers, keeping the following parameters in mind.
This article discussed different types and working of fire extinguishers. We suggest you appear in the SSC JE Mechanical mock tests and SSC JE ME Previous Years Papers. Also, get enrolled in the AE/JE Mechanical coaching to get a firm grip on the subject.
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