Which situation would require the use of helmets among responders at the scene?

The use of helmets among responders at an active shooter incident is primarily necessary in situations where there is a risk of falling debris. During such incidents, particularly in buildings that might have structural damage or in an environment where shots are being fired, responders could be at risk for injuries from objects overhead. Helmets are a critical piece of personal protective equipment designed to safeguard against head injuries that could occur due to falling items or explosive devices.

In scenarios such as firefighting operations, while helmets are also important, they are typically associated with specific firefighting gear and protocols rather than an active shooter situation. Similarly, crowd control situations might necessitate other forms of protective equipment, but they do not inherently involve the same risk of falling debris that an active shooter incident might present. Visibility considerations are relevant in various contexts, but they do not necessitate the use of helmets for protection in the way that falling debris does.