Section 75.1202-1 - Temporary notations, revisions, and supplements(a) Mine maps shall be revised and supplemented at intervals of not more than 6 months.(b) Temporary notations shall include:(1) The location of each working face of each working place;(2) Pillars mined or other such second mining;(3) Permanent ventilation controls constructed or removed, such as seals, overcasts, undercasts, regulators, and permanent stoppings, and the direction of air currents indicated;(4) Escapeways and refuge alternatives designated by means of symbols.35 FR 17890, Nov. 20, 1970, as amended at 73 FR 80697 , Dec. 31, 2008