Special Hazard Suppression Systems Flashcards

What does the acronym 'AFFF' stand for in fire suppression?

Answer: Aqueous Film Forming Foam

AFFF stands for Aqueous Film Forming Foam, named for its ability to form a thin aqueous film over hydrocarbon fuel surfaces to suppress vapors and prevent reignition.

Class K fires, as defined by NFPA, involve which type of fuel?

Answer: Vegetable or animal cooking oils and fats in commercial cooking equipment

Class K fires involve cooking media (vegetable oils, animal fats) at high temperatures in commercial cooking appliances; they require wet chemical agents for effective suppression.

Which inert gas blend, designated IG-541, is marketed under the trade name 'Inergen' and consists of nitrogen, argon, and CO2?

Answer: IG-541 (52% N₂ / 40% Ar / 8% CO₂)

IG-541, sold as Inergen, is a blend of 52% nitrogen, 40% argon, and 8% CO2; the CO2 component stimulates breathing to help evacuating personnel maintain oxygen uptake at reduced O2 levels.

In a CO2 total flooding system, the 'soaking period' refers to:

Answer: The duration the design CO2 concentration must be maintained after discharge to ensure complete fire extinguishment

The soaking period is the post-discharge hold time — typically a minimum specified by NFPA 12 — during which the CO2 concentration must remain at or above the design level to extinguish deep-seated or smoldering fires.

Regarding halon 1211 (bromochlorodifluoromethane) systems after the production phase-out under the Clean Air Act:

Answer: New halon 1211 systems are prohibited, but existing systems may be recharged with recovered or recycled halon

U.S. EPA regulations prohibit new halon production but allow existing systems to be maintained using recovered, recycled, or reclaimed halon, managed through a halon banking system.

For a commercial cooking hood wet chemical system, nozzle placement must provide coverage of which combination of areas per NFPA 17A?

Answer: Cooking surface, hood plenum, and exhaust duct(s)

NFPA 17A requires that wet chemical nozzles protect the cooking appliance surfaces, the hood plenum, and the interior of exhaust ducts to prevent fire from migrating through the ventilation path.

What is the primary fire suppression mechanism of carbon dioxide (CO2) when used in a total flooding application?

Answer: Oxygen displacement — reducing O₂ concentration below the level that supports combustion

CO2 suppresses fire primarily by displacing oxygen in the protected space, reducing the O2 concentration from ~21% to below approximately 15%, which is insufficient to sustain most fires.