Under normal circumstances, how many hours of fire protection must openings in exterior walls have?

Openings in exterior walls are required to have a fire resistance rating based on the potential exposure to fire hazards, and under normal circumstances, a rating of 3/4 hour is generally appropriate. This duration is designed to provide enough time for a building's occupants to safely evacuate in the event of a fire and for firefighters to respond to the emergency.

The 3/4 hour rating allows for reasonable fire protection of openings such as windows and doors, offering a balance between safety and practicality in building design. This standard ensures that the structure maintains its integrity against fire for a crucial period, effectively reducing the risk of fire spreading from one building to another, especially in densely populated or commercial areas.

Ratings of less than 3/4 hour would not provide adequate protection, while ratings higher than this level are typically reserved for more critical elements or zones within a building that may face higher fire loads or risks.