If you’ve ever seen firefighters putting out a fire, either in person or on TV, you’ve probably noticed that they aren’t just hooking up to the fire hydrant and spraying everything down with water (at least in most cases). They’re spraying firefighting foam, which aids in saturating combustible materials and fire suppression. Here’s what you need to know about types of firefighting foam so that you can protect your facilities from fire.
Firefighting foam is a material used for fire suppression. It both coats the fuel for the fire, suppressing combustion and cools the fire. These foams have been around since the beginning of the 20th century and contain surfactants (foaming agents), organic solvents, corrosion inhibitors, and stabilizers.
Class A foams were developed specifically for controlling wildfires, and is now used for class A fires, such as structure fires. They lower the surface tension of the water, which wets fuels and suppresses fire and prevents reignition.
Class B foams are designed for flammable liquids (designated class B fires). Class B foams can be protein foams or synthetic foams. Protein foams contain natural proteins and are generally biodegradable; synthetic foams are made of synthetic foaming agents. These include alcohol-resistant aqueous film-forming foams (AR-AFFF)—which, as the name implies, resist the effects of alcohol and form a protective film—and aqueous film-forming foams (AFFF)—which also form films and are water-based.
Alcohol-resistant foams work specifically to create a protective layer between the foam and the burning material, which prevents the alcohols in the burning material from breaking down the foam and rendering it ineffective.
AFFF foams are low-expansion foams. They are low viscosity and have an expansion rate of less than 20 times. This means that they are mobile and can cover large areas, quickly.
The expansion ratio of medium-expansion foams is 20–100. This makes it useful for applications such as plastic, rubber, and liquid fires or flooding shallow areas.
High-expansion foams are best for enclosed areas that need to be filled quickly, as their expansion rate is over 200–1000.
This is dependent on a variety of factors. If the only and greatest fire risk to your facility is structural, a Class A foam may be appropriate. This isn’t the case for most commercial and industrial facilities, however. A Class B foam is what most situations in manufacturing facilities, petrochemical operations, and even schools will require. Chemicals that can cause or feed fires require Class B foams to limit their actions.
Still have questions about fire fighting foam? We’re here to help. At Vanguard, it’s always our mission to help our clients choose the ideal firefighting foam for their application, that’s exceptionally effective, but that also puts minimal strain on the environment. For more information, be sure to get in touch.