Fire extinguisher facts for kids

A stored-pressure fire extinguisher

A fire extinguisher is a special tool used to put out small fires. It's a handheld device, usually shaped like a cylinder. Inside, it holds a chemical substance, either dry or wet, that helps stop fires quickly. These tools are great for emergencies, but they are not for huge fires that are out of control or too dangerous to approach. If a fire is very big, like reaching the ceiling, or if there's a lot of smoke or a risk of explosion, it's time to call the fire brigade (firefighters)!

There are two main kinds of fire extinguishers:

• Stored-pressure extinguishers keep the extinguishing chemical and the gas that pushes it out in the same container. Nitrogen or air is often used to create this pressure. These are the most common type you'll see.
• Cartridge-operated extinguishers have the gas in a separate small cartridge. When you need to use it, this cartridge is punctured, releasing the gas to push out the extinguishing chemical. These are often found in places like factories where they might be used more often. They can be refilled quickly.

Some fire extinguishers are small enough to carry by hand, weighing from about 0.5 to 14 kilograms (1 to 30 pounds). Larger ones, called cart-mounted or wheeled extinguishers, weigh more than 23 kilograms (50 pounds). You might see these bigger ones at construction sites, airports, or docks.

Wheeled fire extinguisher and a sign inside a parking lot

History of Fire Extinguishers

People have been trying to find ways to put out fires for a long time. The first recorded fire extinguisher was invented in England in 1723 by Ambrose Godfrey. It was a cask of liquid with gunpowder inside. When the gunpowder exploded, it scattered the liquid to put out the fire.

In 1816, British Captain George William Manby showed off a portable, pressurized extinguisher. It used a solution of pearl ash and compressed air to spray liquid onto a fire.

Early Chemical Extinguishers

One important invention was the soda-acid extinguisher, first patented in France in 1866. It mixed water, sodium bicarbonate, and an acid. This reaction created carbon dioxide (CO₂) gas, which pushed out pressurized water to fight the fire.

In 1881, Read & Campbell in England created a cartridge-operated extinguisher that used water. Later, they made one that used carbon tetrachloride (CTC). CTC was good for liquid and electrical fires, but it was found to be harmful to people's health. When heated, it could also create a dangerous gas. Because of these risks, CTC extinguishers were stopped in the 1950s.

A fire grenade

Modern Extinguishers Emerge

The Walter Kidde Company invented the carbon dioxide (CO₂) extinguisher in 1924. This was important for putting out electrical fires because CO₂ does not conduct electricity. CO₂ works by pushing oxygen away from the fire. It is still popular today because it is a clean agent, meaning it leaves no residue.

In 1928, the company DuGas introduced a dry chemical extinguisher. This type used specially treated sodium bicarbonate powder. It was very effective for large liquid and gas fires. Later, different kinds of dry chemical agents, like ABC dry chemical and Purple-K, were developed.

In the 1940s, Germany developed bromochloromethane (CBM) for aircraft fires. It was less harmful than carbon tetrachloride. Later, in the 1970s, Halon extinguishers became popular. Halon agents stop the chemical reaction of a fire. However, Halon was found to harm the Earth's ozone layer, so its use has been greatly restricted since the Montreal Protocol in 1987.

Fire Extinguisher Classes

A British fire extinguisher with ID sign, call point and fire action sign

Fire extinguishers are classified based on the types of fires they can put out. This helps people choose the right extinguisher for a specific fire. Using the wrong type can be dangerous or make the fire worse!

Color Codes and Markings

In many places, fire extinguishers have specific colors or markings to show what's inside.

• In the UK and Europe, extinguishers are mostly red. They have a colored band or circle to show the type of agent. For example, a cream band means foam, and a black band means CO₂.
• In the United States, there isn't one official color standard, but they are often red. They use pictures (pictograms) to show which fire classes they are safe for. For example, a picture of burning wood means Class A.

Where to Install Fire Extinguishers

Automatic engine compartment fire extinguisher installed on a hybrid city bus

Fire extinguishers are usually placed in easy-to-reach spots in buildings, like on a wall in a hallway. They are also found in cars, boats, and airplanes, often required by law. For example, many commercial vehicles must carry at least one extinguisher.

In the United States, there are rules about how high to install extinguishers. They should be easy for everyone to reach, including people using wheelchairs. This means the handle should be no higher than 1.2 meters (48 inches) from the floor. Also, they shouldn't stick out too far from the wall into a walking path, to protect people with low vision.

A dedicated trolley loaded with extinguishers ready to move where needed for rapid use

Types of Extinguishing Agents

Different fire extinguishers use different chemicals to put out fires. Each chemical works best on certain types of fires.

Dry Chemical Agents

These extinguishers use a powder to stop the chemical reactions that keep a fire burning.

• ABC Dry Chemical (Monoammonium phosphate) works on Class A, B, and C fires. It melts and smothers Class A fires. It is a pale yellow powder.
• Sodium Bicarbonate (Regular dry chemical) is for Class B and C fires. It releases a cloud of carbon dioxide gas that pushes oxygen away from the fire. It's not usually good for Class A fires because the gas disappears quickly. It is white or blue.
• Potassium Bicarbonate (Purple-K) is very effective on Class B and C fires. It's often used in the oil and gas industry. It is colored violet.

Foam Agents

Foam extinguishers create a blanket over burning liquids, stopping oxygen from reaching the fire.

• Aqueous Film-Forming Foam (AFFF) is used on Class A and B fires. It forms a film that floats on top of the fuel, sealing the surface. As of April 2024, many traditional AFFF foams are no longer being produced for the US market due to environmental concerns about certain chemicals they contain. Newer, greener formulas are being developed.
• Alcohol-Resistant AFFF (AR-AFFF) is for fires involving liquids like alcohol that can break down regular foam. It creates a special membrane to protect the foam blanket. Like traditional AFFF, many AR-AFFF formulas are also being phased out due to environmental reasons.

Water-Based Agents

Water cools burning materials. It is very good for fires involving wood, paper, and fabrics (Class A). However, water should never be used on electrical fires or flammable liquid fires.

• Stored Pressure Water extinguishers cool fires by turning water into steam. They are inexpensive and easy to clean up.
• Water Mist extinguishers use a fine mist of de-ionized water. This mist does not conduct electricity, so it can be used on Class A and C fires. They are often found in hospitals because they are non-toxic.

Wet Chemical Agents

Wet chemical extinguishers are specifically designed for cooking oil and fat fires (Class K or F). They work by creating a soapy foam blanket over the burning oil. This process, called saponification, cools the oil and stops oxygen from reaching it.

Clean Agents

Clean agents put out fires without leaving any residue. This makes them perfect for protecting sensitive electronics, valuable documents, or aircraft.

• Halon agents stop the chemical reaction of a fire. However, because they harm the ozone layer, their use is now very restricted. Recycled Halon is still used for critical purposes, like in aviation.
• CO₂ (Carbon Dioxide) is a clean gas that puts out fires by pushing oxygen away. It is not for Class A fires, as the gas can scatter burning materials. CO₂ can be dangerous if used improperly, causing cold burns or making it hard to breathe.
• Novec 1230 fluid is a liquid that works by removing a lot of heat from the fire. It is a clean agent and can be discharged as a stream or a mist.

Dry Powder and Metal Fire Extinguishers

These are special extinguishers for fires involving burning metals (Class D).

• Sodium Chloride powder melts to form a crust over the burning metal, cutting off oxygen. It works on many metals like magnesium and titanium.
• Copper-based powder was developed for lithium fires. It smothers the fire and forms a non-combustible alloy on the metal's surface.
• Graphite-based powder also smothers burning metals. It works on magnesium and other metals.

Most Class D extinguishers have a special nozzle to gently apply the powder. This prevents scattering the burning metal.

Fire Extinguishing Balls

Modern fire extinguishing balls have a hard foam shell with a small powder charge inside. When they touch a flame, they burst, releasing a cloud of dry chemical powder to put out the fire. These balls can be placed in fire-prone areas to deploy automatically if a fire starts, or they can be thrown into a fire.

Maintenance of Fire Extinguishers

An empty fire extinguisher which was not replaced for years

Fire extinguishers need regular check-ups to make sure they work correctly when needed. If they are not maintained, they might not discharge or could even burst.

In the United States, fire codes usually require inspections every 30 days to ensure the extinguisher is pressurized and not blocked. A qualified technician also performs an annual inspection and service. They place a tag on the extinguisher to show when it was last serviced. Some extinguishers also need hydrostatic pressure testing every few years, which checks the strength of the cylinder.

New rules allow for electronic monitoring of extinguishers. This system can check if an extinguisher is present, has pressure, and is not blocked. If there's a problem, it sends an alert right away.

A fire extinguisher stored inside a cabinet mounted to a wall

In public places, extinguishers are often kept in cabinets. Sometimes these cabinets have glass that must be broken, or an alarm that sounds if the extinguisher is touched. This helps make sure the extinguisher is only used for real fires and alerts staff if it needs to be checked or replaced.

See also

In Spanish: Extintor para niños

• Fire blanket
• K-factor (fire protection)