225 ILCS 705/31.04

If the air at an underground working face in a mine, when tested at a point not less than 12 inches from the roof, face, or rib, contains more than 1.0% of methane as determined by permissible methane detector, a multi-gas detector, air analysis, or other recognized means of accurately detecting such gas, changes or adjustments shall be made at once in the ventilation in such a mine so that such air shall not contain more than 1.0% of methane.