Question 69 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is C. **Why Option C is Correct:** Option C ("direct the stream of chemical toward the base of the fire") is the fundamental principle for effectively using nearly all types of fire extinguishers, including portable dry chemical units. Fire requires heat, fuel, and oxygen (the fire triangle). The dry chemical agent works primarily by interrupting the chemical chain reaction of combustion (in Class B and C fires) and/or smothering the fuel source (in Class A, B, and C fires). Since the actual burning (combustion) takes place where the fuel meets the heat, directing the agent at the **base** of the fire ensures that the extinguishing agent separates the fuel from the heat source and oxygen, quickly eliminating the fire. **Why the Other Options are Incorrect:** * **A) bounce the chemical onto the fire from adjacent structural members:** This technique is ineffective and wastes the limited agent. It disperses the chemical too widely, preventing a concentrated attack on the fuel source. * **B) attack the fire from the leeward side:** "Leeward" means the side protected from the wind. While fighting a fire with wind present, you should generally attack from the **windward** side (upwind) to avoid having flames, heat, and smoke blown back at you, and to allow the wind to help push the agent toward the fire. Attacking from the leeward side is dangerous and makes effective application more difficult. * **D) spray the chemical across the tops of the flames:** Spraying across the tops of the flames wastes the chemical and does not address the source of the fire (the burning fuel). The chemical must be applied directly to the fuel source to cool it, smother it, or break the chain reaction.