CFPS Special Hazard Suppression 3 — Questions and Answers
Question 1: AFFF (Aqueous Film Forming Foam) suppresses flammable liquid fires primarily by:
- Forming a vapor-suppressing aqueous film and smothering the fuel surface (Correct answer)
- Cooling the fuel below its flash point through water application only
- Chemically inhibiting the combustion chain reaction at the flame front
- Diluting oxygen concentration below 15% above the fuel surface
Correct answer: Forming a vapor-suppressing aqueous film and smothering the fuel surface
AFFF drains an aqueous film ahead of the foam blanket that seals the fuel surface, simultaneously smothering the fire and preventing vapor release.
Question 2: Which NFPA standard covers low-, medium-, and high-expansion foam fire extinguishing systems?
- NFPA 13
- NFPA 11 (Correct answer)
- NFPA 16
- NFPA 15
Correct answer: NFPA 11
NFPA 11 is the standard for low-, medium-, and high-expansion foam systems applied to flammable and combustible liquid hazards.
Question 3: Alcohol-resistant AFFF (AR-AFFF) is specifically required when protecting fires involving:
- Hydrocarbon fuels such as gasoline and diesel
- Polar solvents such as ethanol, acetone, and isopropanol (Correct answer)
- Halogenated hydrocarbons like carbon tetrachloride
- Flammable compressed gases
Correct answer: Polar solvents such as ethanol, acetone, and isopropanol
Polar solvents rapidly destroy the foam blanket of standard AFFF by absorbing water; AR-AFFF forms a polymeric membrane that resists solvent breakdown.
Question 4: High-expansion foam is best suited for which type of fire scenario?
- Open outdoor flammable liquid spill fires
- Enclosed spaces such as basements, mines, or aircraft hangars (Correct answer)
- Three-dimensional flowing liquid fires on vertical surfaces
- Class A ordinary combustibles in open-air storage yards
Correct answer: Enclosed spaces such as basements, mines, or aircraft hangars
High-expansion foam with expansion ratios of 200:1 to 1000:1 rapidly fills enclosed volumes to exclude oxygen, making it ideal for confined space flooding.
Question 5: The expansion ratio range for medium-expansion foam is:
- Up to 20:1
- 20:1 to 200:1 (Correct answer)
- 200:1 to 1000:1
- Greater than 1000:1
Correct answer: 20:1 to 200:1
NFPA 11 defines low-expansion foam as up to 20:1, medium-expansion as 20:1 to 200:1, and high-expansion as 200:1 to 1000:1.
Question 6: Protein foam concentrate is derived from:
- Synthetic petrochemical surfactants
- Hydrolyzed natural protein material such as animal hooves and horns (Correct answer)
- Fluorochemical surfactants bonded to a polymer base
- Synthetic polymer compounds and glycol mixtures
Correct answer: Hydrolyzed natural protein material such as animal hooves and horns
Protein foam is produced by hydrolyzing natural proteins (typically from animal by-products), giving it good heat resistance and drain-down characteristics.
Question 7: When designing a foam-water deluge system for a flammable liquid storage area, the minimum application rate is determined by:
- The type of foam concentrate alone
- NFPA 11 requirements based on fuel type, foam type, and application method (Correct answer)
- Local fire department specifications regardless of NFPA
- The diameter of the largest storage tank only
Correct answer: NFPA 11 requirements based on fuel type, foam type, and application method
NFPA 11 provides application rate tables that account for fuel type, foam concentrate type, and whether application is top-side, subsurface, or semi-subsurface.
CFPS Special Hazard Suppression 3
AFFF (Aqueous Film Forming Foam) suppresses flammable liquid fires primarily by: