225 ILCS 710/45.32

As to all mines which are in operation on the effective date of this section, the distance between the center of the rungs of a ladder shall not exceed fourteen inches and shall not vary more than one-half inch in any one ladder way. As to all mines which are placed in operation after the effective date of this section, the distance between the center of the rungs of a ladder shall not exceed fourteen inches and shall not vary more than one-half inch in any one ladderway and said rungs shall be at least eighteen inches wide and of not less than one inch material free of all defects and shall be morticed into the two supporting timbers their full thickness.