When it comes to battling fires, especially those fueled by flammable liquids, firefighting foam emerges as a crucial tool. 

Understanding the nuances of different foam classes and their specific applications is essential for effective fire suppression.

Firefighting foam is not a one-size-fits-all solution. Different types of foam are designed to combat different types of fires. 

In this article, we’ll explore the various classes of firefighting foam, how they work, their advantages, disadvantages, and alternative options. 

Understanding these aspects will equip you with the knowledge necessary to choose the right firefighting foam for any given situation, ensuring efficient and effective fire suppression.

What is Firefighting Foam?

Firefighting foam is a specialised firefighting agent used for fire suppression, particularly those involving flammable liquids. 

It is a stable mass of small bubbles with a lower density than oil, gasoline, or water.

The foam is designed to cool the flames and prevent oxygen from reaching the fuel, thus extinguishing the fire. 

Firefighting foam is effective because it not only smothers the fire but also seals the fuel vapours, preventing re-ignition.

Firefighting foam comes in different classes, each formulated for specific types of fires. 

Firefighting foam is typically applied using specialised equipment such as foam generators, foam cannons, and foam nozzles. 

It is an essential tool for firefighters and is widely used in industrial, commercial, and military firefighting operations.

Classes of Firefighting Foam

Class A

What is Class A Firefighting Foam Used For?

Class A firefighting foam is specifically formulated to combat Class A fires, which involve solid materials such as wood, paper, and textiles.

It is commonly used in structural firefighting, wildland firefighting, and in situations where water alone may not be effective in extinguishing the fire.

What is Class A Firefighting Foam Made of?

Class A firefighting foam is typically made from a mixture of surfactants, wetting agents, and stabilisers, which reduce the surface tension of water and allow it to penetrate deep into porous materials.

The foam is mixed with water to create a solution that can be applied using firefighting equipment such as foam nozzles and foam cannons.

Examples of Class A Firefighting Foam

Protein-based Foam 

Made from natural proteins such as animal or vegetable proteins. 

Protein-based foams are highly effective for penetrating deep-seated fires and are commonly used in structural firefighting.

Synthetic-based Foam

Made from synthetic materials such as synthetic surfactants and stabilisers. 

Synthetic-based foams are designed to produce a thick, stable foam blanket that can quickly extinguish fires and prevent re-ignition.

Film-forming foam (FFFP)

A combination of Class A and Class B foam, FFFP foam forms a thin film on the surface of the fuel, preventing oxygen from reaching the fire and extinguishing it more quickly.

Class B

What is Class B Firefighting Foam Used For?

Class B firefighting foam is specifically formulated to combat Class B fires, which involve flammable liquids such as gasoline, oil, and alcohol.

It is commonly used in industrial, commercial, and military firefighting operations, as well as in situations where water alone may not be effective in extinguishing the fire.

What is Class B Firefighting Foam Made of?

Like Class A firefighting foam, Class B firefighting foam is typically made from a mixture of surfactants, wetting agents, and stabilisers and allows it to form a blanket over the fuel, preventing oxygen from reaching the fire.

The foam is mixed with water to create a solution that can be applied using firefighting equipment such as foam nozzles and foam cannons.

Examples of Class B Firefighting Foam

Aqueous film-forming foam (AFFF) 

AFFF foam forms a thin film on the surface of the fuel, preventing oxygen from reaching the fire and extinguishing it more quickly. 

It is one of the most common types of Class B firefighting foam and is widely used in industrial and commercial firefighting operations.

Alcohol-resistant aqueous film-forming foam (AR-AFFF)

AR-AFFF foam is specifically designed to combat fires involving alcohol-based fuels such as ethanol and methanol. 

It forms a thick, stable foam blanket that can quickly extinguish the fire and prevent re-ignition.

Fluoroprotein foam

Fluoroprotein foam is a protein-based foam that contains fluorinated surfactants, which make it more effective for extinguishing fires involving hydrocarbon fuels. 

It is commonly used in aviation firefighting and in situations where Class B fires are likely to occur.

What is Firefighting Foam Expansion?

Firefighting foam expansion refers to the increase in volume of foam solution when it is discharged from a nozzle.

How Does Foam Expansion Work?

When foam is discharged from a nozzle, it expands to create a foam blanket that covers the surface of the fuel.

The expansion process is caused by the introduction of air into the foam solution as it is discharged from the nozzle.

Why is Foam Expansion Important?

Foam expansion is an important factor in firefighting because it determines the amount of foam solution required to effectively suppress the fire.

Proper expansion ensures that the foam blanket is thick enough to smother the fire and prevent re-ignition, while minimising the amount of water and foam concentrate used.

Factors Affecting Foam Expansion

Expansion ratios vary depending on factors such as the type of foam, the equipment used, and the application method.

Expansion ratios can range from 2:1 to 20:1 or higher.

Firefighters must be trained to calculate expansion ratios and adjust foam application rates accordingly to ensure effective fire suppression.

What are the Advantages to Using Firefighting Foam?

Firefighting foam is a highly effective tool for suppressing fires, especially those involving flammable liquids. 

Here are some key advantages of using firefighting foam:

Rapid Fire Suppression

Firefighting foam can quickly extinguish fires by forming a thick blanket over the fuel, smothering the flames and preventing re-ignition. 

This rapid suppression helps to minimise damage and reduce the risk of injury or loss of life.

Versatility

Firefighting foam can be used to combat a wide range of fires. 

This versatility makes it a valuable tool for firefighters in various situations, from structural fires to industrial incidents.

Reduced Water Usage

Foam has a lower density than water, which means that less water is required to create an effective firefighting solution. 

This reduced water usage helps to minimise water damage and runoff, making foam a more environmentally friendly option compared to water alone.

Increased Visibility

Foam has a higher visibility than water, which allows firefighters to see where the foam has been applied and ensure that the fire is completely extinguished. 

This increased visibility makes foam a more effective firefighting agent, especially in low-light conditions.

Long Lasting

Firefighting foam can create a long-lasting barrier over the fuel, preventing re-ignition and reducing the need for continuous application. 

This long-lasting effectiveness helps to ensure that the fire remains extinguished and does not reignite.

Cooling Effect

Foam has a cooling effect on the fire, reducing the temperature of the fuel and helping to prevent re-ignition. 

This cooling effect helps to minimise damage to surrounding structures and equipment, making foam an effective tool for protecting property and assets.

What are the Disadvantages to Using Firefighting Foam?

While firefighting foam is an effective tool for suppressing fires, it also has some disadvantages that need to be considered:

Environmental Impact

Some types of firefighting foam contain chemicals that can be harmful to the environment and aquatic life. 

When foam is discharged into waterways, it can contaminate the water and harm marine ecosystems.

However, there has been a large shift in recent years into the use of fluorine free foam, minimising the risk to the environment.

Health Concerns

Firefighting foam can contain toxic chemicals that can pose health risks to firefighters and other individuals exposed to the foam. 

Prolonged exposure to foam can lead to respiratory problems, skin irritation, and other health issues.

Cleanup and Disposal

Firefighting foam can be difficult and expensive to clean up and dispose of properly. 

Foam residue left behind after a fire can contaminate soil and water sources, requiring extensive cleanup efforts.

Cost

Firefighting foam can be more expensive than other firefighting agents such as water or dry chemical agents. 

The cost of purchasing and maintaining foam equipment, as well as the cost of foam concentrate, can add up over time.

Training and Equipment

Using firefighting foam requires specialised training and equipment. 

Firefighters must be trained in the proper use of foam equipment and techniques to ensure effective fire suppression. 

Additionally, foam equipment such as foam generators and foam nozzles can be expensive to purchase and maintain.

What are the Alternatives to Using Firefighting Foam?

While firefighting foam is a highly effective tool for suppressing fires, there are some alternatives that may be more suitable in certain situations:

Water

Water is the most common and widely used firefighting agent. 

It is effective for extinguishing Class A fires involving solid materials such as wood, paper, and textiles. 

Water can also be used in combination with foam for Class B fires involving flammable liquids.

Dry Chemical Agents

Dry chemical agents such as ABC powder and Purple-K powder are effective for extinguishing Class A, B, and C fires. 

They work by interrupting the chemical reaction that sustains the fire, smothering the flames, and preventing re-ignition.

Carbon Dioxide (CO2)

Carbon dioxide is a clean agent that is effective for extinguishing Class B and C fires. 

It works by displacing oxygen, smothering the flames, and preventing re-ignition. 

Carbon dioxide is non-conductive and leaves no residue, making it suitable for use in areas with electrical equipment.

Foam-Water Sprinkler Systems 

Foam-water sprinkler systems combine water with foam concentrate to create a foam blanket that covers the fuel, preventing oxygen from reaching the fire. 

These systems are effective for extinguishing Class A and B fires and are commonly used in industrial and commercial settings.

Fire Blankets

Fire blankets are made of fire-resistant materials and are used to smother small fires or wrap around a person whose clothing is on fire. 

They are effective for extinguishing Class A and B fires and are commonly used in kitchens, laboratories, and welding areas.

Conclusion

Firefighting foam is a versatile tool that plays a crucial role in fire suppression. 

Understanding the different classes of foam and their applications is essential for effective firefighting.

While foam offers numerous advantages, it’s important to weigh these benefits against potential concerns. 

Choosing the right firefighting agent depends on various factors such as the type of fire, the environment, and the availability of resources.

Ultimately, whether firefighting foam is the best choice will depend on the specific circumstances of each fire incident. 

By carefully considering the advantages and disadvantages of foam, firefighters can make informed decisions that prioritise both effective fire suppression and environmental safety.