Which regulation regarding smoking on an aerodrome apron is correct?

The regulation stating that smoking is not permitted except in an enclosed building correctly reflects the high safety standards and precautions necessary on aerodrome aprons. The apron is a sensitive area where various activities, including refueling, maintenance, and passenger handling, take place. These activities create potential fire hazards, making smoking a particularly dangerous action because it increases the risk of igniting flammable materials present on the apron.

By restricting smoking to enclosed buildings, the regulation aims to significantly reduce the possible risks associated with open flames and sparks, ensuring a safer environment for all personnel and operations. This regulation aligns with broader safety protocols established in aviation to mitigate fire risks, thereby supporting the overall integrity of aviation safety.

The other options do not adequately prioritize safety in the specific context of an aerodrome apron, where combined operations and flammable materials are prevalent, leading to much higher risks in case of any fire-related incidents.