The long side of an egress balcony must be open a minimum of ____ %.

The requirement for the long side of an egress balcony to be open a minimum of 50% is grounded in safety and accessibility standards. This criterion is primarily established to ensure that in case of an emergency, such as a fire, the balcony provides a safe escape route by allowing ample airflow and visibility. A balcony that is at least 50% open ensures that occupants have adequate means to exit safely and that they are not confined or trapped.

Having this percentage open aids in preventing potential hazards such as smoke accumulation and increases the effectiveness of any rescue operation. Additionally, it helps in facilitating an efficient evacuation as it reduces the chances of congestion on the balcony during an emergency.

Options suggesting lower percentages like 30% or higher ones like 70% or 90% do not align with the balance of safety and practicality mandated by building codes. Hence, the 50% requirement effectively optimizes safety for the occupants while complying with standards designed to protect life in commercial buildings.