When can non-metallic sheath cable be installed without additional protection?

Non-metallic sheath cable, commonly referred to as NM cable or Romex, is designed for simplicity and versatility in residential wiring. It can be installed without additional protection in dry locations as long as it is not subject to physical damage. This means that if the cable is run through spaces where it is not likely to be hit or crushed, such as within walls, ceilings, or floors, additional protection is not required.

In the context of wiring methods and materials, a critical concern is the physical integrity of the cable. If the cable is exposed to potential hazards that could lead to physical damage — for example, in areas where it may be bumped, punctured, or otherwise compromised — it would require additional protective measures. This is why the focus on installation in dry locations is essential, as moisture or wet conditions could lead to corrosion or degradation of the cable sheath, but this factor is only part of the equation.

The other options provided do not accurately reflect the conditions under which non-metallic sheath cable can be installed without additional protection. Wet locations pose a higher risk for the cable, whereas statements about commercial buildings or all locations being acceptable overlook the critical importance of physical damage risk and environmental conditions.