What is the defining characteristic of an impairing hazard in building safety?

The defining characteristic of an impairing hazard in building safety is the presence of flammable materials. Flammable materials can significantly increase the risk of fire and contribute to the rapid spread of a fire once it ignites. Identifying and managing these hazards is crucial for ensuring the safety of the building and its occupants, as they can compromise fire safety systems and escape routes.

In comparison, while blocked exits, obstructed fire alarms, and high occupancy levels are indeed safety concerns, they pertain more to the accessibility and functionality of means of escape or emergency systems rather than being an inherent characteristic that leads to a fire hazard itself. Flammable materials specifically represent a direct risk that can cause fires to ignite and spread uncontrollably. Thus, recognizing the presence of these materials and mitigating their risk is essential in maintaining building safety.