Fire Apparatus Driver/Operator Chapter 14

The Foam Tetrahedron

• Four elements are required to produce finished foam: a surfactant, a fuel, air, and water.

Foam Extinguishment

• Foam extinguishes flammable liquid fires by creating a barrier between the fuel and oxygen, smothering the fire.
• Foam also cools the fuel, reducing the likelihood of re-ignition.

Types of Foam

• There are two basic types of foam: Class A and Class B.
• Class A foams are used for extinguishing fires involving ordinary combustibles, such as wood, paper, and cloth.
• Class B foams are used for extinguishing fires involving flammable liquids, such as gasoline, oil, and paints.

Expansion of Foam Solution

• Water is essential for the expansion of foam solution.

Hydrocarbon Fuels

• Hydrocarbon fuels separate from water when mixed because they are non-polar and do not mix with water.

Class A Foams

• Class A foams are effective on fires involving ordinary combustibles.
• Class A foams are primarily used for extinguishing fires involving wood, paper, and cloth.

Wetting Agents vs. Foam

• A wetting agent differs from foam in combating fuel fires because it reduces the surface tension of water, allowing it to penetrate and cool the fuel more effectively.
• Foam, on the other hand, creates a barrier between the fuel and oxygen, smothering the fire.

Class B Foams

• Class B foams are designed to extinguish fires involving flammable liquids.
• Class B foams are ineffective on polar solvent and water-miscible fuels like acetone because they do not form a stable foam blanket.

Fuel Resistance

• Fuel resistance refers to the ability of a fuel to resist the extinguishing properties of foam.

Fluoroprotein Foam

• Film-forming fluoroprotein foam is able to form a thin, insoluble film on the surface of the fuel, preventing re-ignition.
• The composition of fluoroprotein foam includes a mixture of protein and fluorinated surfactants.

Aqueous Film-Forming Foam (AFFF)

• The purpose of AFFF is to create a thin, insoluble film on the surface of the fuel, preventing re-ignition.
• AFFF is primarily used for extinguishing fires involving hydrocarbon fuels.

Protein Foams

• Protein foams should be used with a low-expansion nozzle.
• The primary source of protein for protein foams is animal by-products, such as hydrolyzed protein or keratin.

AR-AFFF Foam

• AR-AFFF foam is a type of foam that can be used on both hydrocarbon and water-soluble fuels.
• The primary purpose of AR-AFFF foam is to provide a versatile and effective firefighting agent for a wide range of fuels.

Foam Concentrate Ratios

• The recommended range for foam concentrate ratios for Class B foams is between 1% and 6%.

Foam Expansion Rate

• The foam expansion rate measures the volume of foam produced per unit of foam concentrate.

High-Expansion Foams

• High-expansion foams are highly effective in confined space firefighting operations because they can fill a large volume of space quickly.
• The expansion ratio of high-expansion foam is typically above 200:1.

Low-Expansion Foams

• The foam expansion ratio of low-expansion foam is typically below 20:1.

Medium-Expansion Foams

• The expansion ratio range of medium-expansion foam is between 20:1 and 200:1.

Batch Mixing of Foam Concentrate

• The primary problem with batch mixing of foam concentrate is that it can lead to inconsistent foam quality and quantity.

Eductors

• A fixed eductor is permanently mounted to the fire pump and dedicated to producing foam from a single discharge.
• The necessary inlet pressure for an eductor to overcome friction loss through the eductor and between the nozzle and eductor is typically between 50 and 100 psi.
• The adjustable range of settings for metering devices controlling the flow of concentrate into the eductor is typically between 1% and 6%.

In-Line Eductors

• An in-line eductor should be attached to the hoseline between the nozzle and the surface of the foam concentrate.

Around-the-Pump Proportioning Systems (AP Systems)

• A key advantage of AP systems is that they provide a consistent and accurate foam concentrate ratio.
• The maximum inlet pressure to the water pump on an AP system is typically 100 psi.

Pressure-Controlled Systems

• This type of system uses a diaphragm-type pressure control valve to balance pressures in foam concentrate and water lines.

Injection Systems

• The range of injection rates for foam concentrate in injection systems is typically between 1% and 6%.
• Foam concentrate is injected in injection systems through a metering valve that controls the flow of concentrate into the water stream.

Compressed Air Foam Systems (CAFS)

• A benefit of CAFS is that it provides a high-volume, high-pressure foam solution that can be used for a wide range of firefighting applications.
• A potential problem with CAFS is that it can be difficult to maintain the proper foam concentrate ratio.
• A characteristic of the attack line in a CAFS system is that it uses a compressed air source to generate foam.

Protein Concentrate

• The shelf life range of protein concentrate is typically between 5 and 10 years.

Sweep (Roll-On) Method

• The sweep (roll-on) method should be used when the fire is located at a distance from the nozzle.

Raindown Method

• The raindown method is used when the fire is located above the nozzle, such as in a fuel tank or on a roof.