When should collapse zones be established at an incident?

Setting collapse zones at an incident is crucial for maintaining the safety of responders and bystanders, especially when there is a potential risk of structural failure. The correct choice, which states that collapse zones should be established when the structure has been weakened by exposure to fire, accurately reflects the necessity of assessing the structural integrity of buildings involved in incidents.

When a structure has been subjected to fire, the materials and supports may lose their strength and ability to bear load, leading to a heightened risk of collapse. Establishing a collapse zone is a proactive safety measure to ensure that people remain at a safe distance, effectively mitigating the risks posed by potential falling debris.

In contrast, the other options do not consistently reflect scenarios that necessitate the immediate establishment of a collapse zone. For example, collapsing snow or specific construction types may not always indicate imminent danger on their own. Therefore, it is essential to base decisions regarding collapse zones on the condition of the structure, particularly when compromised by fire exposure.