What rule pertains to smoke rising up a stairway?

The rule that states smoke must not be blocked by a door or obstruction is fundamental in fire safety and building design, particularly in multi-story structures. This principle is rooted in the understanding that during a fire, smoke rises due to its temperature and buoyancy. If smoke is allowed to accumulate in a stairway, it can create a hazardous environment for occupants attempting to escape, as it may reduce visibility and lead to inhalation of toxic gases.

Ensuring that smoke can freely travel upwards without being obstructed allows for proper smoke management, which is critical during an emergency. It also facilitates the effective operation of smoke control systems, which may rely on the natural movement of smoke to function correctly. Having doors or other obstructions in place could trap smoke, creating dangerous pockets of hazardous conditions.

Through this regulation, building designs and fire safety protocols aim to create safer evacuation routes for occupants and to assist fire responders in their efforts to manage smoke and fire hazards.