The stairway enclosed by fire-resistive walls and self-closing rated doors is called a

• A. Smoke proof enclosure
• B. Fire-rated stair
• C. Exit corridor
• D. Protected stairway

Answer: (A)

Stairs that are kept free of smoke during a fire are designed as a smoke-proof enclosure. The fire-resistive walls create a bearing fire barrier, and self-closing doors help seal the enclosure so smoke cannot easily enter the stairwell. This combination keeps the stairway tenable for occupants to use as an exit even as the fire grows elsewhere.

A fire-rated stair refers only to the stair’s own fire resistance rating, not to the surrounding enclosure’s ability to exclude smoke. An exit corridor is a passage, not a stair. A protected stairway describes general protection for the stair path but doesn’t necessarily meet the explicit smoke-control setup described here.