All fire extinguishers work on the basic principle of removing any of the three basic elements needed for combustion—oxygen, heat or fuel. Since their creation two centuries ago, fire extinguishers have played an integral part in saving lives being thretened by a perilous fire.

Basically, there are two types of fire extinguishers: those with internal stored pressure and those where a cartridge system is used to deliver pressure. Cartridge-based systems are more common and are typically used in industrial premises.

Both variants work in more or less the same way—removing one of the three elements of fire’s trinity—oxygen, heat or fuel. This is accomplished by holding the contents within under pressure—either from pressure inside the extinguisher tank or from external cartridges—which can be released in a rapid burst of extinguishing agent when used. When you press the lever on the top of the extinguisher, a valve inside is forced open, releasing the pressurized gas and extinguishing agent through the nozzle.

CHEMICALS INSIDE THE EXTINGUISHER

Now, based on its intended application, a fire extinguisher will contain different chemicals. For example, the fire extinguishers (handheld) that you generally see in residential premises contain pressurized nitrogen or carbon dioxide (CO2) to propel a fire-extinguishing agent to blow out the fire. The active fire extinguishing agent is usually potassium bicarbonate (KHCO3), liquid water, or an evaporating fluorocarbon.

A water sprinkling extinguisher is common in a fixed system, such as a residential apartment tower, as they are inexpensive and safe for people. However, water as an extinguishing agent is not always useful. In a computer or a control room, for example, water could cause short-circuiting, whereas in a fuel storage system, water would barely be effective. Similarly, a water sprinkling extinguisher should not be used in an application where weight and space is limited—such as on an aircraft. In these situations, different chemicals are used. CO2 works well for a room full of computers and servers, but could be fatal if people are also trapped amidst a voracious fire.

Researchers are actively working to develop more chemical combinations that will not only inhibit flames, but also provide cleaner and safer alternatives to the extinguishing agents currently being used that are harmful to the environment. They are also toiling to develop new means of discharging conventional chemicals more effectively, so that the fire extinguishing process can be completed in even less time. One of the ideas making the rounds in the academic circles of fire extinguishing is the use of a solid propellant. This solid propellant would generate an inert gas mixture—an approach similar to the airbag system in your car. Such a system, upon activation, would extinguish fires as easily as we blow out a candle.

That's all🙂

A fire extinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not intended for use on an out-of-control fire, such as one which has reached the ceiling, endangers the user (i.e., no escape route, smoke, explosion hazard, etc.), or otherwise requires the expertise of a fire brigade. Typically, a fire extinguisher consists of a hand-held cylindrical pressure vessel containing an agent which can be discharged to extinguish a fire. Fire extinguishers manufactured with non-cylindrical pressure vessels also exist but are less common.



There are two main types of fire extinguishers: stored-pressure and cartridge-operated. In stored pressure units, the expellant is stored in the same chamber as the firefighting agent itself. Depending on the agent used, different propellants are used. With dry chemical extinguishers, nitrogen is typically used; water and foam extinguishers typically use air. Stored pressure fire extinguishers are the most common type. Cartridge-operated extinguishers contain the expellant gas in a separate cartridge that is punctured prior to discharge, exposing the propellant to the extinguishing agent. This type is not as common, used primarily in areas such as industrial facilities, where they receive higher-than-average use. They have the advantage of simple and prompt recharge, allowing an operator to discharge the extinguisher, recharge it, and return to the fire in a reasonable amount of time. Unlike stored pressure types, these extinguishers use compressed carbon dioxide instead of nitrogen, although nitrogen cartridges are used on low temperature (-60 rated) models. Cartridge operated extinguishers are available in dry chemical and dry powder types in the U.S. and in water, wetting agent, foam, dry chemical (classes ABC and B.C.), and dry powder (class D) types in the rest of the world.