Chapter 23 - Foam

Class A foam can -

-Insulate fuel from radiant heat -Exclude oxygen -Reduce vapor production -Enhance water's ability to penetrate combustibles

Class B foam (3:6)

-flammable and combustible liquids -Once a foam blanket has been applied, it must not be disturbed.

low expansion foam rate

-less than 20:1 -Air is entrained by the flowing stream and mixed into the foam solution. -Often used to apply AFFF or Class A foam

medium expansion foam rate

-ratio between 20:1 and 200:1 -Designed to introduce more air into the stream and produce a consistent bubble structure (aeration) -Typically used in fixed fire-protection systems designed to protect three-dimensional hazard

Most firefighting foams prevent ignition or extinguish fires by...

...creating a foam blanket that isolates the fuel vapors from the heat source and excludes oxygen (in the ambient air) from the burning process.

in a compressed foam system...

...you may have a wetter versus dryer foam

Class A foam mixture

0.1%-1%

The most common type of portable in-line eductor used by fire departments is sized to work with a ____ or ____ attack line

1½ in. (38-mm) or 1¾ in. (45-mm)

Class B foam mixture

3%-6%

Protein foams are made from _______ and tend to spread ________

Animal by-products. Tend to spread slowly

Fluoroprotein foams are the same as _______ along with ______ additives, and tends to spread.

protein foam, fluorochemical surfactant fast-spreading film.

high expansion foam ratio

ratio between 200:1 and 1000:1 -Much greater proportion of air/large bubbles -Uses a high-expansion foam generator to introduce large quantities of air into the discharge stream -Sometimes used in automatic systems that are designed to fill a large space completely -Most likely to be found in aircraft hangars or other large industrial areas

Rain down application method

Consists of lofting the foam stream into the air above the fire and letting it fall down gently onto the surface, Because the stream breaks apart above the fuel surface as it falls, the foam does not disrupt the existing foam blanket or splash fuel, Direct your stream so the entire surface is covered, Good choice for initial application.

Two types of proportioners:

Eductors relies on the venturi system injectors relies on a generator to inject

Aqueous film-forming foam (AFFF)

Is a synthetic-based foam that is particularly suitable for spill-related fires that involve gasoline and light hydrocarbon fuels. -It can form a seal across a surface quickly. -Excellent vapor-suppression capabilities -Can be used on actively burning pools of liquid

Several types of nozzles are used:

Medium- or high-expansion foam generators Master stream foam nozzles Air-aspirating foam nozzles Smooth-bore nozzles Fog nozzles

Roll in application method

Should only be used on a pool of flammable product that is on open ground Performed by directing the foam stream onto the ground in front of the product involved, The stream is moved back and forth in a slow, steady horizontal motion to push the foam forward gently until the area is covered.

CAF

compressed air foam center -Finished product is usually discharged at between 40-125 gal (151-473 L) per minute

Foam is composed of 3 things

concentrate water air (its not until it is airieted that it is turned into foam)

True or False: you cannot mix class A and Class B foam

True

Bounce Off application method

Used at fires where there is an object that can be used to deflect the foam stream and let it flow down onto the burning surface, Sweep the foam back and forth against the object while the foam flows down and spreads.

Class A foams (1 gallon of foam vs 99 water)

Used to fight fires involving ordinary combustible materials Effective on organic materials (carbon based materials)