Foam Flashcards
What is firefighting foam primarily used for?
Suppressing fires by forming a barrier between the fuel and the air.
Name two common types of firefighting foam.
Aqueous Film Forming Foam (AFFF) and Alcohol-Resistant Aqueous Film Forming Foam (AR-AFFF).
What class of fires is Class A foam designed for?
Fires involving ordinary combustibles like wood, paper, and cloth.
What class of fires is Class B foam designed for?
Fires involving flammable liquids like gasoline and oil.
What does AFFF stand for?
Aqueous Film Forming Foam.
What is the primary function of firefighting foam?
To cool the fire and coat the fuel, preventing its contact with oxygen.
What is the typical concentration percentage for AFFF when mixed with water?
3% or 6%.
What does AR-AFFF stand for?
Alcohol-Resistant Aqueous Film Forming Foam.
Why is AR-AFFF used on polar solvent fires?
It resists breakdown when in contact with water-miscible fuels like alcohols.
What is the expansion ratio in firefighting foam?
The ratio of the volume of foam produced to the volume of the original foam solution.
What is a low-expansion foam?
Foam with an expansion ratio less than 20:1.
What is a high-expansion foam?
Foam with an expansion ratio greater than 200:1.
What is the roll-on method of foam application?
Applying foam by rolling it onto the surface of the burning liquid.
What is the bank-down method of foam application?
Applying foam by banking it off a vertical surface to gently flow onto the fire.
What is the rain-down method of foam application?
Applying foam by spraying it into the air, allowing it to fall gently onto the fire.
What does the term ‘foam blanket’ refer to?
The layer of foam that covers and suppresses a fire.
Why is it important to avoid plunging the foam stream directly into the fuel?
It can cause the fuel to splash and spread the fire.
What is the purpose of a foam proportioner?
To mix the correct amount of foam concentrate with water.
What is a foam eductor?
A device that uses the Venturi principle to introduce foam concentrate into a water stream.
What is the typical shelf life of most firefighting foam concentrates?
10 to 25 years, depending on the type and storage conditions.
What is fluorine-free foam (F3)?
Foam that does not contain fluorinated surfactants, designed to be more environmentally friendly.
What is the function of surfactants in firefighting foam?
To reduce surface tension, allowing the foam to spread over the fuel surface.
What is the significance of foam stability?
It determines how long the foam blanket will last before breaking down.
How does foam application rate affect fire suppression?
Insufficient application rates may fail to extinguish the fire, while excessive rates can waste resources.
How do you calculate the required foam solution for a given area?
Multiply the area (ft²) by the application rate (gpm/ft²) and the duration (minutes).
Why is it important to match the foam concentrate to the type of fuel involved?
Different fuels require specific foam properties for effective suppression.
How does temperature affect foam stability?
Extreme temperatures can decrease foam stability and effectiveness.
What is the significance of foam drainage time?
It indicates how quickly the foam releases its water content, affecting cooling and suppression.
Why are fluorosurfactants used in some firefighting foams?
They enhance the foam’s ability to spread and form a film over hydrocarbon fuels.
What is the environmental impact of perfluorooctane sulfonate (PFOS) in firefighting foams?
PFOS is persistent in the environment and can bioaccumulate, leading to health concerns.
How does foam expansion ratio influence its application?
Higher expansion ratios cover larger areas with less water but may be less effective in high-wind conditions.
Why is it important to decontaminate equipment after using firefighting foam?
To prevent corrosion and remove potentially hazardous residues.
What is the difference between foam quality and foam quantity?
Foam quality refers to bubble size and durability, while quantity refers to the volume produced.
What does ‘burn-back resistance’ mean in firefighting foam?
The foam’s ability to resist ignition and maintain a protective blanket over the fuel.
Why is nozzle selection important in foam application?
Different nozzles produce different foam patterns and expansion ratios, impacting effectiveness.
What is a hydrocarbon fuel, and why is it easier to suppress with AFFF?
Hydrocarbon fuels, like gasoline, do not mix with water, allowing AFFF to form an effective film on their surface.
What is a polar solvent fuel, and why does it require AR-AFFF?
Polar solvent fuels, like alcohols, mix with water and can degrade regular foam, requiring alcohol-resistant foams.
What is the importance of foam viscosity?
It affects the foam’s ability to flow over the fuel surface and create a uniform blanket.
Why is high-expansion foam preferred for confined space fires?
It fills large volumes quickly with minimal water, reducing oxygen and cooling the fire.
How do you calculate the total foam solution needed for a spill fire?
Total Foam Solution = fire flow × percent foam × Duration (minutes).
What is the equation to calculate the foam concentrate required?
Foam Concentrate (gallons) = Total Foam Solution × Foam Concentrate Percentage.
How does the Venturi effect work in a foam eductor?
It creates a vacuum by narrowing the water stream, drawing foam concentrate into the water flow.
What is the purpose of using a foam blanket for vapor suppression on hazardous liquid spills?
It prevents vapors from escaping and reduces the risk of ignition or toxic exposure.
What are the three categories of foam expansion?
- Low expansion (<20:1)
- Medium expansion (20:1 to 200:1)
- High expansion (>200:1)
Why is AR-AFFF used for ethanol-based fuels?
Ethanol is a polar solvent that breaks down regular AFFF, but AR-AFFF resists degradation and forms a stable blanket.
How do you calculate the application area for a circular storage tank fire?
Area (ft²) = π × Radius².
What is the significance of foam drain time in fire suppression?
A longer drain time ensures the foam blanket stays intact longer, improving suppression and vapor control.
How do environmental factors like wind affect foam application?
Wind can disrupt foam patterns, requiring adjustments in nozzle angles and application techniques.
Why are protein-based foams less effective on polar solvent fires?
They lack the chemical resistance to withstand polar solvent degradation.
What is a subsurface foam injection system, and where is it used?
It delivers foam below the surface of flammable liquids, typically in storage tanks, to minimize agitation and vapor release.
How does the thickness of a foam blanket affect fire suppression?
Thicker blankets provide better vapor suppression and burn-back resistance but require higher application rates.
How does foam affect the surface tension of water?
Foam reduces surface tension, allowing it to spread more effectively over flammable liquid surfaces.
What is the purpose of hydrolyzed protein in protein-based foam?
It helps create stable bubbles that resist breaking down in heat.
How do you calculate the flow rate needed for a foam monitor?
Flow Rate (gpm) = Nozzle Pressure × Nozzle Flow Coefficient.
What is the impact of foam viscosity on application?
Higher viscosity slows foam flow, improving adherence to vertical surfaces but reducing flow speed.
Why is foam aeration critical for effective fire suppression?
Aeration creates the bubbles that form the foam blanket, improving coverage and vapor suppression.
What is the role of glycol ethers in AR-AFFF?
They provide the foam with alcohol resistance by creating a polymeric barrier over the fuel surface.
How does altitude affect foam system performance?
At higher altitudes, reduced air density can impact aeration and foam expansion.
What is the purpose of a proportioning manifold in foam systems?
It ensures even distribution of foam concentrate to multiple nozzles or application points.
How do you calculate the foam application duration for a given scenario?
Duration (minutes) = Foam Solution Available ÷ Application Rate.
What is the recommended foam blanket thickness for vapor suppression on chemical spills?
4 to 6 inches.
What is the difference between Newtonian and non-Newtonian foams?
Newtonian foams flow consistently under pressure, while non-Newtonian foams change viscosity with applied force.
How does water contamination affect foam performance?
Contaminants can destabilize the foam, reducing its effectiveness in fire suppression and vapor control.
What is the role of a ‘fuel shedding agent’ in advanced foams?
It prevents the foam from absorbing and mixing with the fuel, maintaining the foam’s integrity.
______ sets guidelines for foam systems, application rates, and equipment to ensure effective fire suppression.
NFPA 11
Why are some foams classified as biodegradable?
They break down into non-toxic components in the environment, reducing long-term contamination.
How do you determine foam compatibility with different fuels?
Refer to the foam’s data sheet or compatibility chart, which specifies tested fuel types.
Why is foam rebound important in dynamic fires?
Rebound refers to the foam’s ability to maintain coverage after being disturbed, ensuring continued vapor suppression.
What is the specific gravity range for most firefighting foams?
Typically between 0.95 and 1.02, allowing the foam to float on hydrocarbon fuels.
How does saltwater impact foam performance?
Saltwater can reduce foam stability, requiring the use of salt-resistant foam concentrates.
How do you calculate the area of an irregularly shaped spill for foam application?
Divide the area into simpler shapes (triangles, rectangles), calculate their areas, and sum them.
What is the role of a semi-fixed foam system in industrial applications?
It combines fixed piping with portable equipment for flexible foam deployment.
Why is foam shear rate important in pump systems?
Excessive shear can break down foam concentrate, reducing its effectiveness.
What is the flash point of hydrocarbon fuels typically suppressed by AFFF?
Generally between -45°F and 160°F, depending on the fuel type.
How does foam application rate change for cascading liquid fires?
Higher rates are required to account for flowing fuel and increased vapor production.
How do you calculate the flow rate for a high-expansion foam generator?
Flow Rate (cfm) = Air Flow × Foam Concentrate Ratio.
What is the advantage of fluorine-free foams (F3) in environmental cleanup?
They reduce environmental persistence and eliminate concerns over PFAS contamination.
How does foam application change for cryogenic liquid fires?
Foam must insulate the surface to reduce vaporization and prevent reignition.
How do you calculate the minimum water flow required for foam production?
Water Flow (gpm) = Foam Concentrate Flow ÷ Proportioning Percentage.
Class A proportioned at
0.1-1%
Eduction settings for 125gpm eductor for class A
1/4
1/2
1
Class A foam can help wet class A fuel up to ___ over plain water
20x
Foam bubbles do what?
Create more surface area for rapid heat absorption
Class A foam makes water ____ more efficient
3-5x
Not required for class A foam
Aerator
Cause of surface tension?
Polarity
What does class A do for surface tension?
Breaks polarity, allowing more penetration
Ansulite 3x3 is ____
3%
Universal green foam is 3x3 and ____?
AR synthetic
Fluorine free
What does 3x3 mean?
3% for hydrocarbons
3% for polar solvents
Will classic B foam work if product is moving?
No
Fire flow=
Sq ft x application rate
(0.2)
125 eductor should cover _____ sq ft a min?
1250
Hydrocarbons fuels get _____ foam
Milspec
Polar solvents get ____ foam
AR AFFF ATC
What is the liquid that requires the “AR”
ethanol
How far can the nozzle be from the eductor with a 75psi nozzle and a 125gpm eductor?
250’
How far can the nozzle be from the eductor with a 100psi nozzle and a 125gpm eductor?
150’
How far can the nozzle be from the eductor using the angus 240 and a 250gpm eductor?
300’
Max psi for the 125gpm Akron eductor?
200psi
Max psi for the angus 240?
120psi
Max psi for the 250gpm eductor?
200psi
Max psi and distance for the 95gpm eductors?
200psi
200’
Standard for low/med/high expansion foam
NFPA 11
Amount of finished foam that must be applied to the fire per minute, per sq ft of fire
Application rate
Sq ft x app rate=
Fire flow
Fire flow X eduction rate X min =
Total foam need
Most gasoline’s are ___ hydrocarbon and ____ polar solvent
80%
20%
UL and NFPA define large spill over?
40 sq ft
Foam wand psi?
100
Foam wand gpm
95
Max distance from eductor to foam wand
100’
Foam wand expansion ratio
4:1
Propak
__ gpm
__ psi
__ gallons
12
100
2.5
Required foam for an attack
Fire flow X %foam X minutes
Required foam for attack
Fire flow X _____ X minutes
%foam
Fire flow =
Sq footage X application rate (0.2)
My trick for total foam needed
Sq footage divided by __ for gallons foam over 15 min or ___ for pails needed for 15 min
11
50
