When is it necessary to implement a protective action zone?

Implementing a protective action zone is essential when airborne toxic substances are involved. This is due to the fact that toxic vapors or particles can pose significant health risks to individuals within a certain radius of a hazardous materials incident. Establishing a protective action zone helps to minimize exposure and safeguard public health by preventing people from entering an area that may have harmful air quality.

In contrast, the other options have limitations. While explosion risks are serious, protective action zones are not solely established for explosions; other toxic risks may necessitate their implementation even in the absence of explosion danger. The cleanup phase of an incident primarily focuses on remediation activities, where protective actions may have already been put in place during the initial response phase. Lastly, while it is true that protective action zones should be established according to the specifics of the situation, simply stating "at any time" does not pinpoint the critical conditions that specifically warrant such zones, such as the presence of airborne toxic agents.