It shall be unlawful for any person to operate, maintain or use in any public or quasi-public place or in any building, store or other place where the public is invited any coin-operated dry-cleaning machines, washers or dryers, related items and self-operated car washes unless the proprietor or attendant in charge of the premises where the installation is located is on duty during the prevailing time between the hours of 11:00 p.m. and 6:00 a.m. During the time an attendant is not on continuous duty, there shall be conspicuously posted a telephone number where notice may be given in the event of machine breakdown or some other emergency.