Technical Description

A Description of the Fire Extinguisher and how it works. 

Purpose

The purpose of this technical description is to explain the operation of a fire extinguisher. A fire extinguisher is an emergency tool that is used in situations where time is critical. Learning the inner operating mechanism is important information anyone old enough to stay home alone should know, as it can save a life, and pertains to everyone’s safety. 

Introduction 

The first version of the fire extinguisher was invented in England in 1723 by Ambrose Godfrey. This early model is less recognizable as a fire extinguisher and is more closely related to a squib. It would be thrown into the fire and explode, releasing an extinguishing agent, smothering the fire. This model was seen as ineffective because relying on gunpowder to explode in order to release the solution made it potentially dangerous and unreliable to use. One-hundred years later the first modern fire extinguisher was invented by British Captain George William Manby in 1818. This model had a cylinder with the extinguishing agent, charged with pressurized air which would expel the pressurized solution onto the fire. Since then the fire extinguishers were redesigned and improved, providing us with the current day fire extinguishers. 

External Components

The fire extinguishers external components consist of the cylindrical tank (1), information label (2), valve assembly (3), handle (4), pull pin (5), tamper seal (6), release lever (7), pressure gauge (8), hose (9), nozzle (10) and orifice (11). Modern fire extinguishers are made of steel or aluminum alloy. Some steel cylinders are used for most water and powder-based extinguishers, and some CO2 units, while aluminum alloy cylinders are used for most CO2 extinguishers due to their ability to withstand higher pressure. The modern fire extinguisher can be seen in Figure 2.  

 – The Cylindrical Tank (1) contains the extinguishing solution (12), CO2 cartridge (13), and syphon tube (14). Cylindrical tanks come in several different sizes depending on their use.The most common size is the five pound fire extinguisher which is: 16 ⅞” Height x 5 ¾” Width x 4 ½” Diameter. Most fire extinguishers are red, but some are chrome or have colored bands in which the color of the band at the top of the extinguisher indicates its contents.

 -The Information Label (2) covers a majority of  the cylinder and contains a set of basic information about the fire extinguisher. This includes the extinguishing agent, the fire classification, the ULC Rating, and the instructions for use. Its purpose is to quickly inform the user how to use the fire extinguisher, and to help identify the correct fire extinguisher to use. It also contains the inspection dates, ensuring the fire extinguisher is properly maintained and up to date. 

– The Valve Assemblies (3) regulates the extinguishing agent flow. Composed of the handle (4), pull pin (5), tamper seal (6), release lever (7), and the pressure gauge (8), the valve assembly acts as a trigger to release the agent when needed. 

-The handle is used to lift the fire extinguisher, the tamper seal ensures that the valve assembly or pull pin is not altered and works as intended. The function of the release lever is to allow the extinguishing agent to exit through the hose by pushing the pin (16) that punctures the CO2 cartridge (figure 4). The pin, when not operating, is held up by a spring (17), which prevents the pin from penetrating the CO2 cartridge prematurely.  

-The pull pin is a safety feature, preventing the release lever from accidentally actuating, which would release the agent at an unwanted time. The pressure gauge is a visual indication of the pressure of its contents. When the indicator is past the green zone, this means there is an overcharged condition, where the contents are under too much pressure and can pose an unsafe condition. The indicator being before the green zone means there is not enough pressure in the cylinder to release the agent as intended. The indicator in the green zone means the unit is properly charged and will operate as intended. 

 – The hose (9) is made of PVC (polyvinyl chloride) material, which is a flexible plastic designed to withstand high pressures and prevent ballooning. It is resistant to deteriorating from the chemicals in the extinguishing agent, while remaining kink resistant and easy to handle during use. At the end of the hose there is a nozzle (10) and orifice (11), which help deliver the extinguishing agent. 

– The nozzle’s purpose is to direct the flow of the agent in a controlled direction, ensuring the agent will go to the intended area. The purpose of the orifice is to deliver the agent at a controlled rate by metering the fluid flow. This allows a steady stream of the agent, making the hose easier to operate, and allows a specific amount of time under use, preventing the agent from being released all at once. 

Internal Components

The fire extinguisher contains three main components which are the extinguishing solution (12), CO2 cartridge (13), and syphon tube (14) as displayed in figure 3. The simple internal operations make the fire extinguisher a reliable tool. Consisting three main components allows there to be few parts that can misoperate internally. 

-The extinguishing solution (12) is what takes up a majority of the space in the cylinder. This is the agent that will be used to put out the fire and includes: water, carbon dioxide, foam, dry chemical, and wet chemical. Each agent is responsible for putting out a different type of fire. Fires vary by the material that is burning: solids, liquids, electrical components, and metals. In order for a fire to occur there has to be heat, fuel and oxygen. The extinguishing agent’s role is to eliminate one of these three elements, which will put out the fire. The most common type of agent is dry chemical, and is highly effective against class A, B, and C fires. These agents are designed to be highly effective, and smother the flame, removing the oxygen from the fire, hence putting the flame out. 

– The CO2 Cartridge (13) is a container made of 34CrMo4 steel charged with non-flammable carbon dioxide gas under extreme pressures. The carbon dioxide gas is sealed in the cartridge, reducing pressure stresses acting on the cylinder and on the syphon tube (14). The purpose of the syphon tube is to transfer the agent from the cylinder to the hose. Once the agent gets to the hose, it can be dispersed to the fire. It additionally takes the liquid extinguishing agent from the bottom of the container, ensuring that the expelled agent remains in its liquid form. It also ensures a smooth and steady stream, rather than vapors getting expelled towards the fire, reducing sporadic delivery. 

-The Puncture mechanism (15) consists of the release lever (7), the pin (16), and the spring (17). Its purpose is to release the carbon dioxide gas from the cartridge into the cylinder. It prevents the seal from being punctured when the fire extinguisher is not in use, and also ensures that the seal is ruptured when the fire extinguisher is ready to use. 

Function

The elements of the fire extinguisher function together to effectively put out fires. Once the correct fire extinguisher is identified and verified it is ready for use, the pull pin is removed. This arms the release lever. The hose is aimed at the fire, and the release lever is squeezed with the handle. This downward force pushes the pin. penetrating and rupturing the seal on the CO2 cartridge, expelling the non-flammable carbon dioxide gas. The released gas creates a high pressure inside the cylinder, acting against the extinguishing solution in the cylinder. This force pushes the solution up into the syphon tube, which brings it to the hose, where the agent is released directly to the fire. 

Conclusion

Fires have played—and continue to play—an essential role in our lives: providing warmth, enabling cooking, and shaping communities throughout history, but once they get out of control they create deadly situations where time is of the essence. Fire extinguishers are used worldwide on a daily basis to quickly put out fires before they escalate. They have come a long way from the first model, and have been redesigned to be highly efficient and effective. Its simple internal operations provide a reliable tool that has become highly popular and can be found in almost every home, office space, building, or hardware store. 

 

 Glossary

34CrMo4 Steel – high-strength, low-alloy steel used in many industries. Known for its toughness, abrasion resistance, and fatigue strength. 

Agent – a substance that brings about a chemical or physical effect or causes a chemical reaction.

Alloy – a metal made by combining two or more metallic elements, especially to give greater strength or resistance to corrosion

Arm – pulling the pin to unlock the mechanism and break the seal so that the extinguisher is ready to be used

Ballooning –  swell out in a spherical shape; billow.
Class A, B, C Fires – Fires are classified in six groups A, B, C, D, F and electrical: Class A fires: are fires involving organic solids like paper, wood, etc. Class B fires: are fires involving flammable liquids. Class C fires: are fires involving flammable gasses.

CO2 – carbon dioxide: gas naturally produced by animals during respiration and through decay of biomass

Extinguishing agent- a substance used to suppress or extinguish fires by removing one or more elements of the fire triangle (fuel, heat, and oxygen)

Fire classification  – a system that categorizes fires based on the type of fuel involved

Green Zone – indicates the optimal pressure range, or target area where everything is operating correctly

Squib – a small explosive device that releases fire suppressant from a storage bottle

ULC Rating – indicates that a product has been tested and meets the requirements of Underwriters Laboratories

 

Works Cited 

Bison. “From Its First Invention in 1819, Fire Extinguishers Have Been an Essential Fire Safety Equipment in Every Establishment. This Humble Piece of Equipment Is Everywhere, Even under the Sink or in the Closet of Residential Homeowners.” Linkedin.com, 31 Mar. 2023, www.linkedin.com/pulse/fire-extinguisher-training-how-what-when-use. Accessed 6 Mar. 2025.

“How Is a Fire Extinguisher Made? (Manufacturing Process).” City Fire Protection, 22 Nov. 2021, www.cityfire.co.uk/news/how-is-a-fire-extinguisher-made/.

“History of the Fire Extinguisher.” Fire RangerTM, 11 Feb. 2019, www.fireranger.com/history-of-the-fire-extinguisher/.‌

“Water Fire Extinguisher on Ship, Working, Procedure to Use, Maintenance.” MarineSite.Info, www.marinesite.info/2021/05/water-fire-extinguisher-on-ship-working.html.

‌Woodford, Chris. “How Do Fire Extinguishers Work?” Explain That Stuff, 27 May 2019, www.explainthatstuff.com/fireextinguisher.html.