30 CFR § 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.
