In combustible walls or ceilings, how far back can the front edge of an outlet box or fitting be set from the finished surface?

The correct choice indicates that there are no specified limits on how far back the front edge of an outlet box or fitting can be set from the finished surface in combustible walls or ceilings, meaning that the positioning is not restricted to a set measurement. This allows flexibility in installation based on factors such as wall thickness and the specific requirements of the electrical system or local building codes.

In certain scenarios, outlet boxes may even need to be installed flush with the finished surface to ensure safe and proper functionality, especially in combustible materials. The lack of restrictions can also accommodate variations in construction practices and can enhance the safety and access of electrical components.

Understanding this aspect is critical for ensuring that electrical installations comply with safety standards and best practices, allowing for effective operation without compromising the integrity of combustible materials.