Active face workings shall not be ventilated with air that has passed through a worked-out area or has been used to ventilate a pillar line. This section shall not apply to air that is being used to ventilate an active pillar line or a room that is necessary to establish and maintain such pillar line.
Ventilation with air from certain areas
Va. Code Ann. § 45.2-844, under Chapter 8. Requirements Applicable to Underground Coal Mines; Electricity, Safety, Etc..
Va. Code Ann. § 45.2-844