What is the door rating required for a smoke-proof enclosure?

• A. 20 Minutes
• B. 60 Minutes
• C. 45 Minutes
• D. 15 Minutes

Answer: (A)

The important idea here is how door fire resistance ratings support smoke control in protected egress paths. A smoke-proof enclosure is meant to limit smoke entry into the area people use to escape, giving occupants a safer, tenable route during a fire. The door in that enclosure is rated to resist fire exposure for 20 minutes, which provides enough time to keep the corridor or lobby tenable while evacuation proceeds or the fire is being controlled.

Higher ratings, like 60 minutes, are used for more robust fire barriers or structural enclosures where longer resistance is required. A 15-minute rating is typically too low for a smoke-proof enclosure, and 45 minutes isn’t the standard rating applied to this specific use in most codes.