Question 53 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is D **Why Option D is Correct:** After extinguishing a fire using a fixed smothering agent like CO2, the immediate priority is to ensure the fire is completely out and cannot re-ignite. CO2 extinguishes fire by reducing the oxygen concentration below the level needed for combustion. If the space is opened prematurely (options A, B, or C), fresh air (oxygen) rushes in, which can cause the superheated flammable materials—especially those found in a paint locker, such as paint residues, thinners, and solvents—to spontaneously re-ignite, a phenomenon known as reflash or backdraft. The space must be left closed with ventilation off for a sufficient period (often specified by regulation or procedure, typically at least 15 to 30 minutes, sometimes longer) until the fire has cooled below its ignition temperature, ensuring all boundaries are cool to the touch. **Why Other Options Are Incorrect:** * **A) opened and burned material removed:** Opening the space immediately is extremely dangerous as it introduces oxygen, causing reflash (re-ignition) of superheated materials. Removal of materials should only happen after the space has been fully cooled and ventilated safely. * **B) checked for the proper oxygen level:** While checking the oxygen level is crucial before entry (for personnel safety), this action is performed *after* the necessary cooling period has elapsed and *before* personnel entry. Opening the space just to check the oxygen level immediately after discharge will cause oxygen to rush in, risking reflash. * **C) opened and doused with water to prevent reflash:** Opening the space immediately introduces oxygen, risking reflash before the water can be applied effectively. Furthermore, attempting to douse a confined space fire immediately after CO2 discharge risks personnel safety and is less effective than allowing the boundaries to cool while the space remains sealed and inert.