What is the requirement for vision panels in swinging doors?

The requirement for vision panels in swinging doors is that they are mandatory. This is primarily for safety reasons, as vision panels allow individuals to see through the door before opening it, preventing potential collisions and enhancing visibility in busy areas. Such panels are particularly important in commercial and public buildings where there is a higher likelihood of foot traffic. They help ensure that doors do not obstruct the view of oncoming traffic or people, creating a safer environment for everyone.

In contrast, the other options suggest varying degrees of necessity which do not align with safety regulations typically governing building codes. The use of vision panels is often legislated in order to provide a clear line of sight, thus elevating the safety standards in environments where swinging doors are commonly used.