Transparent glass or plastic doors in commercial or public places in buildings open to the public, must in addition to use of safety glazing materials, be posted, painted, or otherwise marked in such a manner as to alert the public as to their presence in accordance with standards, rules and regulations of the Pennsylvania Department of Labor and Industry. Such posting, painting, or marking shall also be required in those places previously glazed with non-safety glazing materials, prior to the effective date of this act.