Where doors or gates open directly on a stairway, the swing of the door shall not reduce the effective width of the platform to less than how many inches?

The effective width of a platform adjacent to stairways is critical for ensuring safe ingress and egress during emergencies. The requirement that the swing of a door or gate not reduce the effective width of the platform to less than 20 inches is based on safety regulations designed to prevent bottlenecks and facilitate the quick movement of people, especially in emergency situations.

Having a minimum width of 20 inches helps ensure that individuals can easily pass through without obstruction, which is vital in maintaining a clear and accessible escape route. This standard is typically outlined in building codes and fire safety regulations to enhance the level of safety in occupants’ evacuation paths. Adhering to this requirement aids in minimizing risks associated with crowding and maximizes the usability of wide platforms near stairways.

In relation to the options provided, the 20-inch threshold is recognized as the minimum necessary dimension to effectively accommodate these safety needs, making it the correct response.