What feature provides safe vertical egress and smoke protection for occupants in tall buildings?

• A. A fire-rated stairwell (exit stairs)
• B. A mechanical shaft
• C. A smoke vent
• D. A water main

Answer: (B)

Protected, fire-resistance-rated exit stairs provide safe vertical egress and smoke protection. These stairs are enclosed by fire-rated walls and doors and, in many designs, are pressurized to keep smoke out, ensuring occupants can descend safely even while fire and smoke are present on other floors. A mechanical shaft isn’t designed for evacuation and can become a conduit for smoke if not perfectly contained. A smoke vent helps remove smoke but doesn’t guarantee a tenable escape path. A water main is unrelated to occupant egress or smoke control.