Notwithstanding any other provision of this Act, any employer, owner, occupant, lessee, operator, manager, or other person in control of any public place or place of employment may designate a non-enclosed area of a public place or place of employment, including outdoor areas, as an area where smoking is also prohibited provided that such employer, owner, lessee or occupant shall conspicuously post signs prohibiting smoking in the manner described in subsections (a) and (b) of Section 20 of this Act.
410 ILCS 82/30