Shaft enclosures that are 4 or more stories are fire-rated at __ hours.

Shaft enclosures that are four or more stories must be fire-rated at two hours to effectively protect against the spread of fire and smoke between floors. This two-hour rating is essential to ensure that occupants have sufficient time to evacuate in case of a fire and that firefighters can access and operate safely within the building during an emergency response. The fire rating is determined based on building codes and standards, which are designed to minimize risks associated with vertical communication shafts in larger buildings, thereby enhancing overall safety.