In which situation would a fire-resistive wall not require penetration protection?

The correct answer pertains to the specific conditions under which penetration protection may be waived for fire-resistive walls. In scenarios where the annular space around a penetration meets certain defined limits, the need for additional protection can be minimized or disregarded entirely. Annular space refers to the gap created when a pipe or conduit passes through a wall, which can allow fire and smoke to spread if not adequately protected.

When this annular space is maintained within specific tolerances—typically dictated by building codes and fire safety regulations—the fire-resistive characteristics of the wall can remain intact without additional protective measures. This allows for the safe installation of services like electrical conduits while still ensuring the overall integrity of the fire-resistive wall.

Other options do not accurately represent situations under which penetration protection is not required. For example, the mere fact that a box is metallic does not inherently exempt it from required protections; similarly, a wall's thickness alone does not determine whether penetration protection is necessary. Therefore, understanding the importance of maintaining annular space limits is crucial for compliance with fire safety regulations.