IFSTA 7th Edition Chapter 18: Foam Fire Fighting, Liquid Fires, and Gas Fires verified to pass

IFSTA 7th Edition Chapter 18: Foam Fire Fighting, Liquid Fires, and Gas FiresHow does firefighting foam work? - correct answer By forming a blanket of foam on the surface of burning fuels - both liquid and solid What are the 4 methods that firefighting foam extinguishes and/or prevents ignition of fire? - correct answer Separating Cooling Smothering Penetrating Seperating - correct answer Creates a barrier between the fuel gases and possible ignition sources Smothering - correct answer Prevents air from reaching the fuel and mixing with the vapors and prevents the release of flammable vapors Penetrating - correct answer Lowers the surface tension of water and allows it to penetrate fires in class A materials Cooling - correct answer Lowers the temperature of the fuel and adjacent surfaces True/false: class A foam is intended for use in ordinary combustibles and flammable liquids, but class B foam is intended for use of flammable liquids only - correct answer False: Class A is intended for combustibles (class A fires) and Class B foam is intended for flammable liquids How does class A foam work? - correct answer By cooling and penetrating the fuel. It lowers surface tension of water allowing foam/water to penetrate deeper into fuels to extinguish the fire. Works best on porous fuels. Class B foam is especially effective on what two basic categories of flammable liquids? - correct answer Hydrocarbon fuels and polar solvents How is finished foam produced? - correct answer A foam proportioner mixes foam concentrate and water to produce a foam solution. Air is then added to the solution through mechanical agitation, or aeration, to produce the finished foam. Removing any element results in no or poor quality foam. What is foam expansion? - correct answer The increase in volume of a foam solution when it is aerated - expansion is a key characteristic when choosing a foam for a specific application The degree of foam expansion depends on the following factors: - correct answer - Type of foam concentrate used - accurate proportioning - quality of foam concentrate (shelf life or storage conditions) - method of aeration and sizing of bubbles What is the ratio of low-expansion foam? - correct answer 20:1 What is the ratio of medium-expansion foam? - correct answer 20:1 to 200:1 What is the ratio of high-expansion foam? - correct answer 200:1 to 1000:1 Why is it important to thoroughly flush equipment after foam use? - correct answer Foam concentrates have solvent characteristics and are mildly corrosive Class A foam is a special formulation of hydrocarbon based surfactants. How do these surfactants function? - correct answer They reduce the surface tension of water in the foam solution, allowing better water penetration into the fuel How does aerated class A foam work? - correct answer Coats and insulates fuels, preventing pyrolysis and ignition of an adjacent fire.