In what situation must smoke from a stairway not be blocked?

Smoke from a stairway must not be blocked by a door or obstruction because it is critical for both visibility and air quality during an emergency evacuation. Stairways are often designated as primary escape routes in buildings, and any blockage can lead to dangerous situations where people may become trapped or disoriented by smoke. The NFPA 72 emphasizes the importance of clear egress pathways to ensure that the occupants can safely exit the building in the event of a fire. Doors or other obstructions could stop smoke from ventilating or clearing from the stairway, which could prevent safe passage.

In contrast, while blocking smoke with furniture or large objects, wall decorations, or electrical installations may not be ideal, they do not carry the same level of urgency in terms of life safety when compared to the immediate and critical need for keeping egress routes clear of smoke.