Mezzanines or portions thereof are not required to be open to the room in which they are located, as long as the aggregate floor area of the enclosed space is a maximum of what percentage of the mezzanine?

The correct answer is based on the code provisions regarding mezzanines in commercial buildings. Mezzanines provide additional floor space but must comply with certain regulations to maintain safety and accessibility. One such regulation allows for portions of a mezzanine to be enclosed, provided that the total enclosed area does not exceed 10% of the area of the mezzanine.

This restriction serves a crucial safety purpose: it helps ensure that the mezzanine retains its classification as a space that enhances access and visibility while preventing overcrowding or obstruction of movement. If the percentage of enclosed space were higher, it could potentially compromise the safety features associated with open spaces, such as emergency egress and overall structural integrity. Thus, keeping the enclosed area to a maximum of 10% ensures that mezzanines remain functional spaces without exceeding necessary safety limits.

In comparison, higher percentage limits would likely result in more complications concerning safety, accessibility, and occupancy regulations, which is why the lower limit is prescribed.