225 ILCS 705/5.15
He shall take daily barometer readings and record the readings when men are in the mine, and keep a careful watch over all ventilating apparatus and the air currents in the mine. When the ventilating fan at any mine fails or stops, he shall take immediate action to cut off the electric power and withdraw the workers from the face regions of the mine. In gassy mines, if the ventilation is restored within a reasonable time, the face regions and other places where methane is likely to accumulate shall be re-examined by competent personnel, and if such places are found to be free from explosive gas the power may be restored and work resumed. If the ventilation is not restored within a reasonable time all underground employees shall be removed from the mine. In non-gassy mines, if the ventilation is restored within a reasonable time, the power may be turned on and the work resumed without the necessity of re-examination.
225 ILCS 705/5.15