(1) Fresh air shall be admitted to required ventilation-openings contained in external walls directly from the open air, from a court or a street or public place, or else from a roofed porch, veranda or balcony (hereinafter referred to as a “covered area”), complying with subsection (2).

(2) Covered areas supplying outside air to required ventilation-openings to habitable rooms shall not extend more than 4,5 metres away from the face of the wall at a required ventilation-opening:

Provided that such covered areas to habitable rooms in a dwelling may be enclosed, if ventilation-openings, complying with the requirements of subsection (2) of section 5, equivalent to 7 ½ per centum of the combined floor areas of the provided in an external wall.

(3) Where any habitable room has only one external wall containing ventilation-openings, the required ventilation-openings contained in internal walls of the room shall be supplied with air from passages or ducts which communicated with—

a) The open air at points situated either in the roof or in an external wall; or

b) In the case of dwellings, an approved ventilated passage or room which is not a sleeping-apartment.

(4) Where, in a dwelling, a room opens directly into a passage which supplies air to ventilation-openings in an internal wall of any habitable room, it shall be sufficient, if ventilation, in the form of fanlights, is provided to such passage from another room or rooms having an external wall which does not face in the same direction as the external wall of the room concerned:

Provided that no noxious fumes or gases shall be able to enter such passage from any other room.

(5) In all buildings, other than dwellings, a passage which supplies air to ventilation-openings in an internal wall of any habitable room shall be ventilated directly to the open air at least at one end, or shall be mechanically ventilated.