Mine rescue tracings must be maintained with ventilation controls, safety installations, and essential underground working details. A below-ground mine must maintain more than three legible tracings of the mine workings, each updated to a date not earlier than three preceding months. The tracings must accurately depict the ventilation system and associated controls, including the general direction of air-current, points of air measurement, air-crossings, ventilation-doors, stoppings, booster fans and other principal devices for regulation and distribution of air.