Sr. Design and Project Engineer
Plumbing and Fire Fighting System
Bachelor of Technology (B. Tech) in Mechanical Engineering
from Regional Engineering College (REC/NIT), Hamirpur (HP)
Member of Kuwait Society of Engineers (KSE)
Kuwait Fire Force License (KFD Card)
Contact : +965 94074747, E-mail : kamal.mech.engg@gmail.com, +91-9041049598 (whatsapp)
Portable Fire Extinguishers
Portable fire extinguishers apply an extinguishing agent that will either cool burning fuel, displace or remove oxygen, or stop the chemical reaction so a fire cannot continue to burn. When the handle of an extinguisher is compressed, agent is expelled out the nozzle.
Classification of Fires (Types of Fires)
If a fire starts, it can spread quickly. Not every fire is the same. Different fires can have different hazards and risks. Using the wrong type of fire extinguisher could do more harm than good. There are 6 different types of fire, and each should be attacked in a different way. There are 6 different classes of fire, and each should be attacked in a different way.
Class A (Solids)
Class A fires are fires involving solids. This type of fuel could be paper and cardboard, common in offices and manufacturing. It could be furniture, or fixtures and fittings. It could even be the structure of the building.
Class B (Liquids)
Class B fires are fires involving liquids. Many of the fluids, liquids and chemicals used in workplaces can be flammable or explosive. Like cleaning fluids, solvents, fuels, inks, adhesives and paints.
According to statistics, in 2010/11 flammable liquids accounted for only 2% of fires, but a massive 21% of fatalities. These fires are rare but more deadly than other types of fire.
Class C (Gases)
Class C fires are fires involving gases. This could be natural gas, LPG or other types of gases forming a flammable or explosive atmosphere. Work with gas is dangerous, and increases fire risk. Keep stored gases in sealed containers in a safe storage area, and ensure that gas work is carried out by competent persons. While extinguishers can be used on class C gas fires, the only safe method to attack this type of fire is to shut off the gas supply.
Class D (Metals)
Metals are not often thought of as a combustible material, some types of metal can be, like sodium. Metals are also good conductors, helping a fire spread. All metals will soften and melt at high temperature, which can be a big problem when metal joists and columns are present in a fire as structural elements.
Electrical Fires
This is not strictly a class (class E) of fire, because electricity is more or a source of ignition than a fuel. However, fires in live electrical equipment are an additional hazard. You don't want to be using water, or any other conductor as that could be fatal.
"Electrical fires are not given their own full class, as they can fall into any of the classifications. After all it is not the electricity burning but surrounding material that has been set alight by the electric current".
Class F (Cooking Fats & Oils)
Deep fat frying and spillages of flammable oils near to heat sources in kitchens can result in a class F fire.
Never leave food or frying equipment unattended during use. The only type of fire extinguisher approved for use on cooking oils and fats is the wet chemical extinguisher. For small class F fires, you could also use a fire blanket.
Types of Fire Extinguishers
Different types of fire extinguishers are designed to fight different types of fire. The three most common types of fire extinguishers are: air pressurized water, CO2 (carbon dioxide), and dry chemical. The following table provides information regarding the type of fire and which fire extinguisher should be used.
Water - Air-pressurized Water Extinguishers (APW)
Water is one of the most commonly used extinguishing agents for type A fires. You can recognize an APW by its large silver container. They are filled about two-thirds of the way with ordinary water, then pressurized with air. In some cases, detergents are added to the water to produce a foam. They stand about two to three feet tall and weigh approximately 25 pounds when full.
APWs extinguish fire by cooling the surface of the fuel to remove the "heat" element of the fire triangle.
APWs are designed for Class A (wood, paper, cloth, rubber, and certain plastics) fires only.
Important:
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Never use water to extinguish flammable liquid fires. Water is extremely ineffective at extinguishing this type of fire and may make matters worse by the spreading the fire.
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Never use water to extinguish an electrical fire. Water is a good conductor and may lead to electrocution if used to extinguish an electrical fire. Electrical equipment must be unplugged and/or de-energized before using a water extinguisher on an electrical fire.
CO2 or Dry Chemical - Carbon Dioxide Extinguishers
This type of extinguisher is filled with Carbon Dioxide (CO2), a non-flammable gas under extreme pressure. These extinguishers put out fires by displacing oxygen, or taking away the oxygen element of the fire triangle. Because of its high pressure, when you use this extinguisher pieces of dry ice shoot from the horn, which also has a cooling effect on the fire.
You can recognize this type of extinguisher by its hard horn and absent pressure gauge.
CO2 cylinders are red and range in size from five to 100 pounds or larger.
CO2 extinguishers are designed for Class B and C (flammable liquid and electrical) fires only.
Important:
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CO2 is not recommended for Class A fires because they may continue to smolder and re-ignite after the CO2 dissipates.
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Never use CO2 extinguishers in a confined space while people are present without proper respiratory protection.
Locations:
Carbon dioxide extinguishers will frequently be found in industrial vehicles, mechanical rooms, offices, computer labs, and flammable liquid storage areas.
Multi-purpose - Dry Chemical Extinguishers
Dry chemical extinguishers put out fires by coating the fuel with a thin layer of fire retardant powder, separating the fuel from the oxygen. The powder also works to interrupt the chemical reaction, which makes these extinguishers extremely effective.
Dry chemical extinguishers are usually rated for class B and C fires and may be marked multiple purpose for use in A, B, and C fires. They contain an extinguishing agent and use a compressed, non-flammable gas as a propellant.
ABC fire extinguishers are red in color, and range in size from five pounds to 20 pounds.
Dry Chemical extinguishers will have a label indicating they may be used on class A, B, and/or C fires.
Locations:
These extinguishers will be found in a variety of locations including: public hallways, laboratories, mechanical rooms, break rooms, chemical storage areas, offices, commercial vehicles, and other areas with flammable liquids.
Class K - Dry and Wet Chemical Extinguishers for Kitchen Fires
Due to the higher heating rates of vegetable oils in commercial cooking appliances NFPA 10, Portable Fire Extinguishers, now includes a Class K rating for kitchen fires extinguishers which are now required to be installed in all applicable restaurant kitchens. Once a fire starts in a deep fryer, it cannot always be extinguished by traditional range hoods or Class B extinguishers.
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Do not attempt to use a Class A extinguisher containing water or CO2 on a deep fat fryer fire. An explosive type reaction may result.
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Place a placard near the Class K fire extinguisher which states: "In case of appliance fire, use this extinguisher only after the fixed fire suppression system has been actuated". Class K fire extinguishers are only intended to be used after the activation of a built-in hood suppression system. If no commercial cooking system hood and fire suppression system exists, Class K extinguishers are not required.
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Extinguishing agents in many Class K extinguishers are electrically conductive and should only be used after electrical power to the kitchen appliance has been shut off. Class K extinguishers use a variety of agents. Potassium bicarbonate is used in some Class K dry chemical extinguishers, and there are also Class K wet chemical extinguishers which spray a fine mist.
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Travel distance to a Class K extinguisher shall not exceed 30 feet.
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Install a 2-A water-type extinguisher or 6L wet chemical fire extinguisher for solid fuel cooking appliances with fire boxes.
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Inspect, test and maintain Class K fire extinguishers yearly.
Locations:
These extinguishers will be found in commercial cooking operations such as restaurants, cafeterias, and other locations where food would be served.
Fire and Extinguisher Operation
Fire Triangle:
To understand how fire extinguishers work, you need to understand a little about fire. Fire is a very rapid chemical reaction between oxygen and a combustible material, which results in the release of heat, light, flames, and smoke.
For fire to exist, the following four elements must be present at the same time:
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Enough oxygen to sustain combustion.
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Enough heat to raise the material to its ignition temperature.
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Some sort of fuel or combustible material.
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The chemical reaction that is fire.
How a Fire Extinguisher Works:
Portable fire extinguishers apply an extinguishing agent that will either cool burning fuel, displace or remove oxygen, or stop the chemical reaction so a fire cannot continue to burn. When the handle of an extinguisher is compressed, agent is expelled out the nozzle.
All portable fire extinguishers must be approved by a nationally recognized testing laboratory to verify compliance with applicable standards. Equipment that passes the laboratory's tests are labeled and given an alpha-numeric classification based on the type and size of fire it will extinguish.
Let's take a look at the label pictured. The classification is:
1-A:10-BC
The letters (A, B, and C) represent the type(s) of fire for which the extinguisher has been approved.
The number in front of the A rating indicates how much water the extinguisher is equal to and represents 1.25 gallons of water for every unit of one. For example, a 4-A rated extinguisher would be equal to five (4 x 1.25) gallons of water.
The number in front of the B rating represents the area in square feet of a class B fire that a non-expert user should be able to extinguish. Using the above example, a non-expert user should be able to put out a flammable liquid fire that is as large as 10 square feet.
Extinguishers Color Coding
Use of Fire Extinguishers
Fire extinguishers can be heavy, so it's a good idea to practice picking up and holding an extinguisher to get an idea of the weight and feel. Take time to read the operating instructions and warnings found on the fire extinguisher label. Not all fire extinguishers look alike. Practice releasing the discharge hose or horn and aiming it at the base of an imagined fire. Do not pull the pin or squeeze the lever. This will break the extinguisher seal and cause it to lose pressure.
When it is time to use the extinguisher on a fire, just remember PASS!
Pull the pin.
Aim the nozzle or hose at the base of the fire from the recommended safe distance.
Squeeze the operating lever to discharge the fire extinguishing agent.
Starting at the recommended distance, Sweep the nozzle or hose from side to side until the fire is out. Move forward or around the fire area as the fire diminishes. Watch the area in case of re-ignition.
