What is the minimum requirement for a fireproof door in smoke-proof enclosures?

In smoke-proof enclosures, the minimum requirement for a fireproof door is typically designated as providing a fire-resistance rating of 20 minutes. This duration is considered sufficient to ensure that the door can withstand direct flames and high temperatures for a critical period, allowing occupants to evacuate the building safely while also restricting the spread of smoke and fire. The 20-minute rating is a standard in building codes for doors that protect openings in walls that are critical for maintaining the integrity of smoke barriers or other fire-resistive assemblies. This ensures that such enclosures can effectively contribute to the overall safety strategy in a building, particularly during emergencies.

Longer durations, such as 30 minutes or more, are applicable in some situations, but for the specific context of a smoke-proof enclosure, the 20-minute requirement aligns with regulatory standards intended to provide adequate protection while minimizing evacuation risks.