This map pictures a smaller underground mine.  The yellow line indicated the location of the beltline which carries the coal outside.  The green line is a water line which is installed to supply water for dust control and to cool the motors of  the continuous miner.  The blue arrows indicate where fresh air  is forced into the mines by a fan.  This air is necessary  to ventilate the work area and to eradicate dust and methane from the area..  The pink arrows indicate the return air which is carried back outside the mines.
 
 

        This map below pictures a large underground mine.  The solid blocks indicate areas that have been pillared, meaning the whole block of coal has been extracted leaving no roof support.  The letter "B" indicates Bleeder Blocks which are left for ventilation purposes.  The letter "L" indicates Leave Blocks which are left to support above-ground structures such as homes, roads, cemeteries, gas wells, etc.