Smoke-proof enclosures are stairways designed to limit the penetration of which substance?

• A. Flammable Liquids
• B. Radiation
• C. Hoselines
• D. Toxic Gases

Answer: (D)

Smoke-proof enclosures are built to keep a stairwell as free as possible from smoke and the toxic gases produced by burning materials. The danger in a fire isn’t only heat; it’s the mixture of smoke and hazardous gases that can overwhelm people quickly. By using fire-rated walls, self-closing doors, and proper sealing, these enclosures limit the intrusion of smoke and toxic products of combustion into the stairway, preserving a tenable escape route. The other items—flammable liquids, radiation, and hoselines—aren’t the primary focus of these structures. In short, the main purpose is to restrict toxic gases and smoke from penetrating the stairwell.