Which characteristic defines a high-rise building's capability in fire events?

The characteristic that defines a high-rise building's capability in fire events is the presence of significant stack effect challenges. In high-rise buildings, the stack effect refers to the movement of air in and out of the structure due to temperature differences between the interior and exterior. During a fire event, hot air rises, creating pressure differentials that can affect smoke movement and overall building ventilation.

One of the critical concerns in fire safety for high-rise buildings is how this stack effect can lead to quicker smoke spread, potentially compromising evacuation routes and increasing the risk to occupants. This phenomenon can complicate firefighting efforts as well since it may draw smoke into upper floors, creating hazardous conditions for both occupants and first responders.

The other options, while relevant to fire safety, do not specifically capture the unique challenges presented by high-rise buildings in fire events as clearly as the stack effect does. Minimal evacuation time or effective outside fire attacks, for instance, may be concerns for fire safety in general but can vary significantly based on the building's design and fire protocols. Evacuation being completed in less than 30 minutes is a standard time frame that does not necessarily pertain to the inherent characteristics of high-rise structures.