Final answer:
Class B fire extinguishers are used for petroleum fires and utilize a fluorinated solution or foaming agents to spread across and extinguish the fire. Carbon tetrachloride is no longer used due to toxic gas production.
Step-by-step explanation:
The class of fire extinguisher used for a petroleum fire is Class B. These extinguishers are designed to fight fires involving flammable liquids and gases like gasoline and petroleum. A fluorinated solution in these extinguishers can spread across the burning surface and extinguish the fire efficiently. Traditionally, carbon tetrachloride was used in fire extinguishers for electrical fires, but it has been discontinued due to the production of toxic phosgene gas.
Fighting a petroleum fire presents unique challenges because petroleum products like gasoline have high energy content, and burning just one liter can release around 2.80×107 J of energy. Special formulations are required for fire extinguisher systems that may include foaming agents to effectively fight such high-energy fires. These agents, like foaming plastics, help by isolating the fuel from the oxygen and cooling the fire.