Not all fires are the same: paper in an archive, cooking oil in a pan, gas escaping from a pipe or, in certain industrial environments, a metal can catch fire. This is why different types of fire extinguishers exist, each designed to tackle specific fire classes.
Using the wrong extinguisher may, at best, prove ineffective; at worst, it can make the situation worse.
This is clearly explained in a video by Geopop, a scientific communication project, which explores the subject through practical examples and demonstrations, under the technical supervision of the Italian Fire Brigade.
For those of us working in the fire safety industry, the video also features a familiar detail: fire extinguisher valves.
Types of fire extinguishers and fire classes: the key differences
Fires are classified according to the material that is burning. European standards distinguish five fire classes, identified by the letters A (solids), B (flammable liquids), C (gases), D (metals) and F (cooking oils and fats). Each class requires specific extinguishing agents (water, foam, powder), which act on the combustion process in different ways.
For this reason, every fire extinguisher label indicates the extinguishing agent it contains and the fire classes for which it is suitable.
In short, different types of fire extinguishers are not interchangeable.
A typical example is cooking oil catching fire in a frying pan: if water is poured onto it, as one might instinctively do, it instantly evaporates and splashes burning oil in all directions, spreading the flames instead of putting them out. The correct action is to smother the flames with a lid, provided the fire is still contained and it is safe to intervene, or to use a Class F fire extinguisher.
Fire classes and suitable extinguishers: summary table
A - Solids: wood, paper, textiles, plastics - Suitable fire extinguishers: Water, foam or powder extinguishers
B - Flammable liquids: petrol, solvents, paints - Suitable fire extinguishers: Foam, powder or CO2 extinguishers
C - Gases: methane, LPG, hydrogen - Suitable fire extinguishers: Powder extinguishers
D - Metals: magnesium, potassium, sodium - Suitable fire extinguishers: Special metal fire powder extinguishers
F - Cooking oils and fats - Suitable fire extinguishers: Specific Class F fire extinguishers
This table helps identify the appropriate type of fire extinguisher according to the fire classification, but it does not replace the instructions on the extinguisher label or the precautions required to intervene safely.
Choosing a fire extinguisher according to the type of fire and the environment
The choice of fire extinguisher depends on the type of fire most likely to occur in the environment where it will be used. ABC powder extinguishers are commonly used in homes and apartment buildings, as they are suitable for tackling fires involving solid combustible materials, flammable liquids and gases. For kitchens, as mentioned above, a Class F extinguisher is the most suitable option.
In offices and technical rooms, the presence of computers, electrical panels and other electrical equipment may make CO2 extinguishers a suitable choice. They leave no residue and are suitable for certain applications involving live electrical equipment. In workshops, garages and laboratories where solvents, paints or fuels are used, the presence of flammable liquids points towards foam or powder extinguishers. In workplaces, the type and number of fire extinguishers are determined by the fire risk assessment.
In the Geopop video, you can see the differences between the various types of fire extinguishers and discover, through practical demonstrations, how to use them correctly.
What happens when we squeeze the lever of a fire extinguisher?
The video also illustrates the PASS technique, a four-step sequence for using a fire extinguisher: pull the safety pin, aim the nozzle at the base of the flames, squeeze the lever and sweep the discharge from side to side.
Two of these actions – pulling the safety pin and squeezing the lever – involve a component that is not widely known: the valve.
The valve is the point of contact between the person using the fire extinguisher and its contents. When at rest, it keeps the extinguisher closed and holds the extinguishing agent under pressure. When the lever is squeezed, the valve's shut-off mechanism opens, allowing the pressure to push the extinguishing agent towards the discharge outlet. Releasing the lever causes a spring to close the passage again: discharge can therefore be stopped and resumed, allowing the agent to be dispensed as needed during the intervention.
The action itself takes just a moment, but the valve must be ready to perform it even after years of inactivity. It must maintain pressure tightness over time, open on the first operation and ensure a steady flow compatible with the extinguishing agent inside.
The fire extinguishers used in the video's demonstrations are also fitted with valves designed and manufactured by CPF, specifically developed for different extinguishing agents.
- CO2 fire extinguishers are fitted with a brass squeeze-grip valve designed to contain high-pressure liquefied carbon dioxide. For this reason, it incorporates a safety device: a calibrated rupture disc that breaks in the event of abnormal overpressure, releasing the gas in a controlled manner.
- Stored-pressure powder fire extinguishers, in which the extinguishing agent is constantly pressurised and ready for use, feature a dedicated squeeze-grip valve. The valve includes a pressure gauge connection, which allows users to check at a glance whether the extinguisher is charged, as well as a safety device calibrated between 20 and 24 bar.
- For water and foam fire extinguishers, CPF manufactures a dedicated valve with a swivel connection, simplifying installation and removal.
All three valves are certified in accordance with European Directive 2014/68/EU (PED) on pressure equipment.
Types of fire extinguishers and their use: fire safety starts before an emergency
Knowing the different types of fire extinguishers and understanding which one to use for each fire class is the first step. However, as the video reminds us, safety starts well before an emergency occurs: knowing where fire extinguishers are located (at home, in the office or in the apartment building), being familiar with evacuation plans and carrying out a few simple visual checks.
Tackling an incipient fire requires trained people and reliable equipment. Scientific communication helps prepare the former, while the design and manufacture of components contribute to the reliability of the latter.
If you haven't watched it yet, take a look at the Geopop video and share it: it could prove useful to someone when they least expect it.
