After extinguishing a paint locker fire using the fixed CO2 system, the next immediate action is for the space to be __________.

Correct Answer: Option B — left closed with ventilation off until all boundaries are cool

Following fixed CO2 discharge, boundaries remain closed with ventilation de-energized to prevent oxygen re-introduction. This thermal soaking period ensures all surrounding steel and structural materials cool completely below the autoignition temperature of the paint or solvents.