Foam Application and Types

Foam Application and Types

• Smooth bore nozzles are restricted to Class A foam from a CAFS (Compressed Air Foam System).
• A variable flow rate sensing proportioner is needed to supply a fire stream at 0.1 to 1.0 percent due to low eduction rates on a CAFS apparatus.
• The decomposition of foam consumes oxygen.
• Class B synthetic foam concentrate is made from a mixture of fluorosurfactants.
• As firefighting foam breaks down, water is released, which cools the fuel and suppresses heat-producing oxidation.
• Foam's degree of expansion is most affected by the method of aeration.
• Batch mixing is generally used with Class A and regular AFFF concentrates.
• A foam proportioner injects the correct amount of foam concentrate into the water stream to create the foam solution.
• A key reason to avoid direct application of Class A foam to natural bodies of water is the potential harm to aquatic life.
• High-expansion foam is suited for combating concealed space fires in cellars or other subterranean spaces.
• In-line foam eductors are basic foam proportioners designed for direct attachment to the pump panel discharge or hose lay.
• Mil-Spec concentrates are foam concentrates manufactured to U.S. Military specifications.
• Fire apparatus with onboard foam proportioning systems typically have foam concentrate tanks piped directly to the delivery system.
• A partially closed nozzle can prevent the creation of a Venturi effect, impacting foam production when using an in-line proportioner.
• The application rate is the minimum amount of foam solution used per minute per square foot of fire.
• Pails are the smallest type of foam storage container.
• Biodegradability is determined by the rate at which natural bacteria degrade foam.
• A shared characteristic of all foam storage containers is airtight storage.
• A bypass proportioner can be installed in some in-line eductor systems to reduce friction loss across the eductor.
• A disadvantage of durable agents is that surfaces coated with them can become very slippery.
• Self-educting master stream foam nozzles have a pickup tube in the nozzle's center bore and use a modified Venturi design.
• High-energy foam generating systems/CAFS introduce compressed air into the foam solution before discharge into the hoseline.
• A fog nozzle is a common handline nozzle used for foam application.
• To calculate the application rate available from a nozzle, divide the flow rate by the area of the fire.
• Frothing during batch mixing can be avoided by slowly circulating water in the tank.
• Whether the fuel is contained or uncontained affects a foam's rate of application.
• Batch mixing is potentially inaccurate.
• Variable-flow demand-type balanced pressure proportioners use a variable speed mechanism to operate a foam concentrate pump.
• For a portable foam application device, the foam solution must be aerated after foam concentrate and water are mixed.
• The best consistency of Class A foam for vertical surfaces is dry foam, as it forms a rigid, well-adhering coating that drains slowly.
• Limitations of CAFS include the intensification of a hose burst reaction due to compressed air.
• Class A foam solutions lose their foaming properties when mixed in water for more than 24 hours.
• Class A foam formulas include hydrocarbon surfactants, which reduce the surface tension of water.
• The two basic types of medium- and high-expansion foam generators are water aspirating and mechanical blower.
• Foam nozzles work in conjunction with proportioners to produce the best possible foam.
• The act of mixing water with foam concentrate to form a foam solution is called proportioning.
• Alcohol and ketones are examples of polar solvent fuels that require special polymeric firefighting foam.
• Firefighting foam requires foam concentrate, water, and air educted or injected in the correct ratios.
• Aqueous film forming foam (AFFF) consists of fluorochemical and hydrocarbon surfactants combined with solvents to create a high boiling point.
• Air-aspirating foam nozzles induct air by Venturi action, suited for protein and fluoroprotein concentrates.

Foam Application Methods and Equipment

• The bank-down method involves directing foam onto a vertical surface to spread across pooled fuel.
• Premixing proportioning uses premeasured portions of water and foam concentrate mixed in a container.
• Durable agents are used in a similar fashion to Class A foam.
• Low energy foam systems use the main fire pump to impart pressure on the foam solution.
• Installed in-line eductors are commonly used to proportion Class B foam.
• It is acceptable to mix foam concentrates from different manufacturers if they are mil-spec concentrates.
• Both medium- and high-expansion foam generators produce foam with high air content.
• Direct application is best used with Class A foam.
• Temperature most likely affects the viscosity (thickness and ability to flow) of a liquid.
• The flow in gallons per minute (L/min) through the eductor must not exceed its rated capacity when operating an in-line foam eductor.
• Regular protein foams degrade more quickly and are becoming increasingly rare.
• Fog nozzles allow firefighters to operate fixed, selective, or automatic flow when applying foam.
• A jet ratio controller is a type of in-line eductor for supplying foam concentrate to a self-educting master stream foam nozzle.
• Ambient air temperature affects the breakdown process of Class A foam.