Firefighting Foam Flashcards
What types of fires are foaming agents effective in controlling and extinguishing?
Class A and B fires
Class A fires involve ordinary combustibles, while Class B fires involve flammable liquids.
What are the main components of foaming agents?
Biodegradable fluorocarbon and hydrocarbon surfactants
These components are diluted with water to create the foam.
Why is foam particularly effective on Class B fires?
It can float on the surface of liquids
This property allows it to effectively smother the fire.
What factors affect the effectiveness of foam?
Rate of application, expansion ratio, and stability of the foam
These factors determine how well the foam can control a fire.
How is low- and medium-expansion foam usually produced?
By injecting concentrate into a fire stream via an eductor
This foam is discharged through a fog nozzle or specialty foam tube.
What is a Compressed Air Foam System (CAFS)?
A system used to produce low- and medium-expansion foam
It utilizes compressed air to enhance foam generation.
How is high-expansion foam generated?
Mechanically using a powered foam generator
This can be powered by an engine or water.
What are the primary functions of foam in firefighting?
- Creates a barrier between the fire and the fuel
- Cools the temperature of the fuel and adjacent surfaces
- Smothers the fire by preventing air from reaching the fuel
- Lowers the surface tension of water for better penetration of Class A materials
What is the Roll-on Method of applying foam?
Foam stream is directed at the front edge of a burning liquid
The foam rolls across the surface until the entire area is covered.
When is the Rain-down Method used?
When the fire or spill area is too large or there is no object to bank the foam
The foam is directed into the air to fall gently onto the surface.
Describe the Bank-down Method of applying foam.
Foam stream is directed at an elevated object near a Class B fire
The foam runs down the surface onto the liquid’s surface.
What is the expansion ratio of low-expansion foam or aqueous film-forming foams (AFFF)?
10:1
What types of fires is AFFF best used on?
Two-dimensional fires, Class B fires such as fuel spills
What is the effectiveness of AFFF on three-dimensional Class A fires?
Limited effectiveness
What principle do in-line hose or nozzle eductors use to introduce foam concentrate?
Venturi principle
How does water under pressure affect the eductor in an in-line hose or nozzle eductor?
Creates low pressure within the eductor
What type of foam hardware can AFFF be used with?
Both aspirating and non-aspirating mechanical foam hardware
What is the purpose of aspirating nozzles in foam application?
To entrain air into the diluted foam-water solution