All persons, firms or corporations which own or have control of any public pay toilets shall cause the same to be equipped with devices, approved by the Commissioner of Public Health, to keep them clean and sterile. Each such person, firm or corporation shall maintain and equip at least one free public toilet in each restroom. At least one-half of any additional toilets in each restroom shall be free. Every public toilet shall be equipped with a door which may be locked by the occupant. Any such person, firm or corporation which fails to comply with the provisions of this section shall be fined not more than five hundred dollars.