Exit passageway enclosures must have walls, floors and ceilings that have a minimum fire-resistance rating of ___ hour(s).

The correct answer is that exit passageway enclosures must have walls, floors, and ceilings with a minimum fire-resistance rating of 1 hour. This requirement is established to ensure that these enclosures can adequately protect occupants during a fire emergency, allowing for safe egress from a building.

The 1-hour fire-resistance rating is tied to the need for providing occupants enough time to evacuate safely before the structure becomes compromised due to fire. This fire rating means that the materials used in these enclosures can withstand exposure to fire for at least one hour, slowing the spread of flames and smoke into the passageway.

Higher ratings, such as 2, 3, or 4 hours, are typically reserved for more critical elements or where there may be a greater risk of fire, such as in high-rise buildings or areas with more occupants. In the context of exit passageway enclosures, the 1-hour rating strikes a balance between safety, construction feasibility, and code compliance.