Fire Safety Basics: Understanding Fire Classes and How To Extinguish Them

Fire safety is an indispensable aspect of our daily lives, whether at home, in the workplace, or in public spaces. One of the foundational elements of fire safety is understanding the different fire classes.

Each class represents a specific type of fire, based on the materials or factors that ignite it. By distinguishing these classes, we can determine the most effective methods to extinguish them and, more importantly, prevent them from occurring in the first place.

In the UK, fire-related incidents are a significant concern. According to UK government statistics, there were approximately 178,737 fire incidents in the year ending March 2023. An increase of 7.8% compared to the previous year. These incidents led to 259 fatalities.

These numbers underscore the critical importance of being informed and prepared. By gaining a comprehensive understanding of fire classes, we can equip ourselves with the knowledge to respond effectively to fires, potentially saving lives and reducing property damage.

Fire Classes

Fire safety can seem complex, but understanding the different fire classes is a pivotal starting point. Each fire class categorises the various types of fires based on the materials that ignite them.

By familiarising ourselves with these fire classes, we can better equip ourselves to prevent, manage, and extinguish fires effectively and safely.

Class A: Combustible Materials (Solids)

Class A fires are caused by the ignition of combustible materials that are commonly found in both domestic and commercial settings. Examples of these materials include:

• Wood
• Paper
• Textiles
• Straw
• Coal
• Most plastics
• Dry leaves and grass

These materials, often referred to as 'carbonaceous materials', can easily catch fire when exposed to a heat source, making them a frequent cause of fires.

Prevention Tips:

1. Store combustible materials away from heat sources, such as heaters, stoves, and open flames.
2. Ensure proper disposal of waste materials like paper, cardboard, and wood shavings.
3. Regularly inspect and maintain electrical equipment to prevent sparks that can ignite these materials.
4. Keep workspaces and homes tidy, reducing the accumulation of combustible materials.
5. Install smoke alarms in areas where these materials are stored or used frequently.

How to put out a Class A fire:

• Water extinguishers: These cool the fire, removing the heat source.
• Foam extinguishers: These smother the fire and cool the burning material.

Class B: Flammable Liquids

Class B fires are ignited by flammable liquids or materials that become liquid at the point of ignition. Common culprits include:

• Petrol
• Diesel
• Solvents, such as paint thinners and certain cleaning agents
• Alcohols, like methanol and ethanol
• Oils, excluding cooking oils
• Tar
• Certain paints

These liquids have a low flash point, meaning they can ignite easily when exposed to a heat source or even a spark.

Storage and Safety Tips:

1. Store flammable liquids in well-ventilated areas away from direct sunlight or heat sources.
2. Use safety containers or cabinets specifically designed for flammable liquids.
3. Ensure that storage areas are equipped with spill containment measures to prevent the spread of any accidental spills.
4. Keep flammable liquids away from electrical equipment or outlets to prevent accidental ignition.
5. Always use flammable liquids in well-ventilated areas to prevent the buildup of flammable vapors.
6. Use grounding and bonding techniques when transferring flammable liquids to reduce the risk of static electricity igniting vapors.

How to put out a Class B fire:

• CO2 (Carbon Dioxide) extinguishers: These displace the oxygen the fire needs to burn.
• Dry powder extinguishers: These can smother the fire and interrupt the chemical reaction.
• Foam extinguishers: These seal the surface of the liquid, preventing flammable vapors from reaching the air and smothering the fire.

Class C: Flammable Gases

Class C fires involve flammable gases, which can be highly explosive when mixed with air and exposed to an ignition source. Common gases that fall under this category include:

• Propane
• Butane
• Methane
• Hydrogen
• Natural gas
• Acetylene

These gases are commonly used in various applications, from cooking and heating to industrial processes, making them prevalent in many settings.

Storage and Safety Tips:

1. Store gas cylinders upright in well-ventilated areas, away from direct sunlight, heat sources, and flammable materials.
2. Ensure that gas cylinders are regularly inspected for leaks or damage.
3. Use gas detectors in areas where flammable gases are stored or used to alert in case of leaks.
4. Always turn off gas supplies at the source when not in use.
5. Ensure proper ventilation when using flammable gases to prevent the buildup of explosive concentrations.
6. Avoid using open flames or sparks near areas where flammable gases are stored or used.

How to put out a Class C fire:

• Cut off the gas supply.
• Dry powder extinguishers: These can interrupt the chemical reaction of the fire.
• CO2 (Carbon Dioxide) extinguishers: These displace the oxygen the fire needs to burn.

It's essential to note that the primary goal with a Class C fire is to shut off the gas supply. Once the gas source is turned off, the fire will often self-extinguish. However, if the fire continues, it's then treated based on the type of material that's burning, be it Class A or B. Always ensure that the chosen extinguisher is regularly checked and is easily accessible in case of an emergency.

Class D: Combustible Metals

Class D fires involve metals that can combust, especially in the form of shavings, powder, or swarf. These types of fires are less common but can be extremely intense when they occur. Metals that can ignite and fall under this category include:

• Magnesium
• Titanium
• Zirconium
• Sodium
• Potassium
• Lithium
• Aluminum (in powdered form)

These metals, when exposed to moisture or air under certain conditions, can react and ignite, leading to a Class D fire.

Storage and Safety Tips:

1. Store combustible metals in a dry environment, away from moisture and oxidising agents.
2. Handle metal powders with care, avoiding any sparks or flames during processing or storage.
3. Clean up metal shavings or powders promptly to prevent accumulation, which can increase the risk of ignition.
4. Use safety equipment, such as flame-resistant gloves and eye protection, when working with combustible metals.
5. Ensure that workspaces are well-ventilated to prevent the buildup of any flammable metal vapors or dust.

How to put out a Class D fire:: For Class D fires, specialised fire extinguishers are required, as using a standard extinguisher can exacerbate the fire.

• Dry powder extinguishers specifically formulated for metal fires, often referred to as "Class D" extinguishers. These extinguishers work by smothering the fire and absorbing the heat the fire produces.
• Some specific metal fires, like lithium fires, might require a unique extinguishing agent.

It's crucial to be aware of the specific metal involved in the fire to choose the right extinguishing method.

Class E: Electrical Fires

Class E fires involve electrical equipment or energised electrical circuits. These fires can be caused by short circuits, overloaded electrical outlets, faulty wiring, or malfunctioning electrical appliances. Examples of scenarios that can lead to Class E fires include:

• Overheated circuit breakers or fuse boxes
• Faulty electrical appliances like toasters, microwaves, or space heaters
• Damaged power cords or outlets
• Overloaded power strips or extension cords

It's essential to note that while the electrical source may initiate the fire, the actual flames can spread to nearby combustible materials, making it a combined fire hazard.

Storage and Safety Tips:

1. Regularly inspect electrical installations and appliances for signs of wear, damage, or malfunction.
2. Avoid overloading electrical outlets or using damaged cords and plugs.
3. Ensure proper grounding of electrical appliances and circuits.
4. Use circuit breakers and fuses that match the correct amperage ratings for their circuits.
5. Keep electrical equipment clean and free from dust or debris, which can be combustible.
6. Ensure that electrical appliances have adequate ventilation to prevent overheating.

How to put out a Class E fire:: For Class E fires, it's crucial to use non-conductive extinguishing agents to avoid electrical shock.

• CO2 (Carbon Dioxide) extinguishers: These displace the oxygen the fire needs to burn and are non-conductive.
• Dry powder extinguishers: These can smother the fire and interrupt the chemical reaction, but it's essential to ensure the electrical source is turned off as they can be conductive.

Remember, the first step in dealing with an electrical fire is to shut off the electricity if it's safe to do so. Once the electrical source is turned off, the fire becomes one of the other classes, depending on the materials ignited.

Class F: Cooking Oils and Fats

Class F fires are specifically related to cooking oils and fats. These fires can be particularly challenging to deal with because of the high temperatures involved. Common scenarios leading to Class F fires include:

• Overheated frying pans or deep fryers
• Spillovers from cooking pots or pans containing oils or fats
• Ignition of residual oils on stovetops or ovens
• Cooking oils coming into contact with open flames

Storage and Safety Tips:

1. Always monitor cooking processes, especially when frying or using large amounts of oil.
2. Use thermostats in deep fryers to prevent oils from overheating.
3. Keep cooking areas clean and free from residual oils or grease, which can ignite over time.
4. Avoid filling pots or pans with too much oil, reducing the risk of spillovers.
5. Ensure good ventilation in the cooking area to prevent the buildup of vapors that can ignite.

How to put out a Class F fire: For Class F fires, water should never be used as it can cause the hot oil to splatter, potentially spreading the fire.

• Wet chemical extinguishers: These are specially designed for Class F fires. They work by creating a soapy layer over the surface of the burning oil, cooling it and preventing re-ignition.
• Fire blankets: These can smother smaller fires in pans or pots, cutting off the oxygen supply.

It's crucial to approach Class F fires with caution, as the high temperatures involved can lead to severe burns. If a fire gets out of control, it's always safest to evacuate the area and call the emergency services.

Fire Extinguisher Guide

Selecting the appropriate fire extinguisher is not just a matter of safety; it's a matter of life and property. Using the wrong type of extinguisher can not only be ineffective but can also exacerbate the fire, leading to more significant damage or danger.

For instance, using a water-based extinguisher on an electrical fire can result in electrocution. Understanding the different types of extinguishers and their applications is paramount.

Fire Extinguisher Comparison

Maintenance and Location Tips for Fire Extinguishers

1. Regular Inspection: Fire extinguishers should be inspected at least once a month. Check for any visible signs of damage, ensure the pressure gauge is in the green zone, and check the manufacturing date. Extinguishers typically have a lifespan of 10-12 years.
2. Annual Maintenance: Have a professional fire safety expert inspect and service your extinguishers annually. They can check internal components, recharge if necessary, and ensure they're in working order.
3. Accessible Location: Extinguishers should be placed in easily accessible locations, free from obstructions. They should be mounted on walls or placed in stands where they can be quickly grabbed in an emergency.
4. Signage: Ensure that there's clear signage indicating the location of fire extinguishers, especially in large buildings or premises.
5. Training: Ensure that family members or staff are trained on how to use an extinguisher. Knowing how to use the PASS (Pull, Aim, Squeeze, Sweep) technique can be crucial during a fire.
6. Recharge After Use: Even if an extinguisher has been partially used, it should be recharged or replaced to ensure it's effective for future use.

By understanding the different classes of fires and the appropriate extinguishers to use, combined with regular maintenance and proper placement, you can ensure a safer environment, whether at home or in the workplace.

What Next?

It's evident that knowledge is our most potent tool against the unpredictable nature of fires. Understanding the distinct fire classes and their characteristics is not just a matter of compliance or ticking off a checklist; it's about safeguarding our homes, workplaces, and communities.

Each fire class presents its unique challenges, and being equipped with the right information can mean the difference between a minor incident and a major catastrophe.

Be sure that your fire safety and fire stopping responsibilities are being assessed and met to ensure your building and occupant safety.