Which term describes the protective enclosure for stairwells consisting of fire-resistance rated walls and self-closing doors?

Which term describes the protective enclosure for stairwells consisting of fire-resistance rated walls and self-closing doors?

• A. Smoke proof enclosure
• B. Fire refuge chamber
• C. Protected shaft
• D. Egress lobby

Answer: (A)

A smoke-proof enclosure is the protective stairwell enclosure built with fire-resistance rated walls and self-closing doors to keep smoke out and maintain a tenable path for egress during a fire. This term specifically describes the stair enclosure itself—the vertical shaft that must resist smoke infiltration so occupants can safely evacuate. The other terms refer to different concepts: a fire refuge chamber is a designated safe room for occupants to shelter in place, not the stair enclosure; a protected shaft is any vertical shaft (like elevator or mechanical ducts) that is fire-rated but not limited to a stairwell; and an egress lobby is a transitional space near exits, not the actual stair enclosure.

A smoke-proof enclosure is the protective stairwell enclosure built with fire-resistance rated walls and self-closing doors to keep smoke out and maintain a tenable path for egress during a fire. This term specifically describes the stair enclosure itself—the vertical shaft that must resist smoke infiltration so occupants can safely evacuate. The other terms refer to different concepts: a fire refuge chamber is a designated safe room for occupants to shelter in place, not the stair enclosure; a protected shaft is any vertical shaft (like elevator or mechanical ducts) that is fire-rated but not limited to a stairwell; and an egress lobby is a transitional space near exits, not the actual stair enclosure.