225 ILCS 710/45.37

In vertical workings not exceeding 100 feet in depth or height, ladders may be fixed vertically; no vertical ladders shall be used with a greater height or depth than 100 feet. Provided, however, that around every such vertical ladder, collars or platform shall be built which shall be not more than 20 feet apart and shall be constructed as provided by section 45.35 of this Act.