C. However, any ordinance may provide that employers may regulate smoking in the private work place as they deem appropriate under the following circumstances: (i) if the designation of smoking and no-smoking areas is the subject of a written agreement between the employer and his employees, the provisions of the written agreement shall control such designation and (ii) a total ban on smoking in any work place shall only be enforced by the employer upon an affirmative vote of a majority of the affected employees voting, unless such ban is the subject of a contract of employment between the employer and the employees as a prior condition of employment. No ordinance adopted pursuant to this subsection shall affect no-smoking policies established by employers prior to the adoption of such ordinance.