In each tenement house erected or subdivided after June 30, 1941, there shall be a water closet in each apartment of two or more rooms. In each tenement house erected after August 31, 1930, and prior to July 1, 1941, there shall be a water closet in each apartment of three or more rooms and at least one water closet for each two apartments of less than three rooms each. Each water closet shall be in a separate compartment or bathroom, upon the same floor with the apartment which it accommodates. Each bathroom, toilet room or other room containing one or more water closets or urinals, which is placed in any building, shall be at all times provided with adequate lighting and shall be ventilated in at least one of the following ways: (1) By a window opening directly upon a street or other open public space or upon a court located on the same lot as the building, and having, between stop beads, an area not less than ten per cent of the floor area nor less than three square feet in any case and a width of not less than one foot; (2) by a window of the size specified in subdivision (1) of this section, or a register, opening on a vent shaft which extends to and through the roof or into a court conforming to the requirements of this section for courts and which has a cross-sectional area of not less than one-fifth of a square foot for each foot of height but not less than nine square feet and a width of not less than sixteen inches in any case, and, unless open to the outer air at the top, a net area of louvre openings in the skylight equal to the maximum required shaft area; (3) by an individual vent flue or duct extending independently of any other flue or duct to and above the roof and having a cross-sectional area of not less than one square foot for two or fewer water closets or urinal fixtures and one-third of a square foot additional for each additional water closet or urinal fixture; (4) by a skylight in the ceiling, having a glazed surface of not less than three square feet and arranged so as to provide ventilating openings of not less than three square feet to the outer air above the roof of the building or into a court conforming to the requirements of this section for courts, for two or fewer water closets or urinal fixtures and two square feet additional for each additional water closet or urinal fixture; or (5) by some approved system of mechanical exhaust ventilation of sufficient capacity to provide not less than four changes of air per hour. Each vent shaft in a tenement house erected after August 31, 1930, shall be constructed of fire-proof material. Not more than two water closets or bathrooms shall open upon such a shaft on one floor of a tenement house, and no two water closet or bathroom windows opening upon such shaft on the same floor shall be opposite each other.