Firefighting foam is a key part of successful firefighting. This unique firefighting tool was developed more than a century ago to fight oil fires that were problematic to water application. Since its creation, firefighting foam has changed from its original formula, but its main job has remained the same. Today, it is still used to knock down and secure burning and unignited flammable liquids. Class A foams are also used on ordinary combustibles to help water become more effective in fire extinguishment.  

In this article we are going to explore what firefighting foam is and how it helps firefighters extinguish a fire. 

What is Firefighting Foam 

Class B foams used in flammable liquid firefighting are a mixture of foam concentrate, water, air, and mechanical agitation that creates a foam blanket to cover a fire. Aqueous Film Forming Foams (AFFF) have been a staple in the fire service for many years, but we now know they contain long-lasting chemicals that can invade ground water and may cause cancer or other illnesses in those exposed to the foam. To combat this, the fire industry is turning to Fluorine Free Foam (F3) and equipment optimizations that make the best use of this product.  

A variety of equipment can be used to apply foam to a fire. Portable foam systems, foam tubes, foam eductors, self educting nozzles, and handheld or fixed and portable monitor nozzles are used to properly mix and apply foam on a fire hazard. What is used may depend upon the type of foam, type of fire, desired foam expansion rate, and more. 

When firefighting foam is used on a fire, the foam blanket smothers the fire, removes oxygen, reduces heat, and creates a barrier that mitigates vapor release. If you are familiar with the fire tetrahedron, or fire triangle (oxygen, heat, fuel), these items are needed for a fire to burn. If you remove even one of these pieces, the fire goes out. Foam is a tool that can tackle the fire tetrahedron in several ways. 

Why do Firefighters Use Firefighting Foam 

Firefighters use foam for several reasons: 

•  Applying water to flammable liquids poses many challenges. Foam application shows significant advantages in extinguishment time over water, and vapor seals the hazard. 

• Foam stays on top of the liquid and smothers it by creating a physical separation or barrier to exclude oxygen from flammable vapors. It also removes heat from the liquid and surrounding surfaces. 

• Flammable liquids release vapors into the air. Firefighting foam creates a vapor barrier that prevents this vapor from escaping upward. This provides a safer environment for firefighters and individuals nearby or downwind from the fire hazard. 

• In some cases involving ordinary combustibles, water needs to penetrate more deeply to fully extinguish the fire and to prevent rekindling. This is where Class A Foam is used. One of Class A Foam’s features is that it lowers the surface tension of the water it is mixed with, allowing it to penetrate more deeply into the fuel. 

Firefighters can use foam to safely and effectively extinguish fire when water is ineffective or problematic or would create a hazard on its own. As you can see, firefighting foam is an important firefighting tool and when properly used, can lead to positive outcomes and faster fire suppression.