If a nerve agent is present in the atmosphere, when can you safely remove your protective mask?

The correct answer is based on standard protocols for chemical exposure, particularly concerning nerve agents. Protective masks are critical for safety in contaminated environments, as they filter out harmful agents from the air. The all-clear signal indicates that a thorough assessment has been made, confirming that it is safe to remove your protective gear. This means that the presence of the nerve agent has been either effectively countered or eliminated, and the environment has been deemed safe for unprotected breathing.

Timing, visibility, and elapsed duration (such as one hour or two hours after an attack) are not adequate indicators of safety when dealing with nerve agents, which can remain hazardous long after their initial release and may not necessarily be visible. Therefore, relying on an official all-clear signal provides the most reliable assurance of safety before removing protective equipment.