What is the required duration for exit enclosures for buildings with 4 stories or more?

For buildings that are four stories or more in height, the required duration for exit enclosures is typically set at 2 hours. This requirement is based on the need to provide a safe means of egress for occupants during emergencies, allowing them sufficient time to exit the building safely while also providing structural integrity and firefighting access.

The 2-hour rating for exit enclosures is designed to withstand fire for an extended period, preventing the fire from spreading to the escape route and ensuring that the enclosure remains usable during an evacuation. This duration offers a buffer for the fire service to manage the incident before the exit route potentially becomes compromised.

In the context of fire safety codes and regulations, the time-based ratings reflect a consensus on how long a structure needs to maintain its integrity to protect individuals within the building. This reinforces the importance of proper construction methods and materials being utilized in taller buildings, where the risks associated with fire can increase.