Every lamp, extension light, and permissible form of portable illumination, such as a cap lamp or flashlight, that is used for personal illumination underground shall be inspected by an authorized person at least once per week, and more often if necessary, to ensure safe operating conditions. When such equipment is located at the surface, it shall be inspected by an authorized person at least once per month, and more often if necessary, to ensure safe operating conditions. Any defect found shall be corrected.