225 ILCS 710/45.45

Drifts used as manways intersecting overhead workings through which material is dropped shall be closed to the passage of persons by a substantial rail not less than 3 1/2 feet nor more than 4 feet in height above the level of the drift, on each side of the working, whenever material is to be dropped through such working, and the drift shall be kept so closed during the period when the working is so in use.