What requirement is there for a listed electrical box installed in a fire-resistive wall without additional penetration protection?

In the context of installing a listed electrical box in a fire-resistive wall, it is essential that the annular space around the box adheres to specific fire safety standards to maintain the fire-resistive integrity of the wall. When the annular space exceeds certain dimensions, it can compromise the effectiveness of the fire-resistive properties of the wall, allowing flames and heat to pass through more easily.

The requirement that the annular space must not exceed 1/8” ensures that there is minimal gap between the electrical box and the wall. This small allowance helps to prevent the rapid spread of fire and smoke, as larger gaps could create a pathway for flames to breach the wall. Thus, maintaining this specification is critical for fire safety and compliance with building codes.

Other options, such as the materials or specific dimensions of the box, while important in their own right, do not directly address the fire-resistive integrity as the annular space does. Therefore, focusing on controlling the size of the gap is a crucial requirement in this context.