(a) Where gas-fueled heaters are permitted to be installed in lieu of the required centrally supplied heat, each "living room," as such term is defined in subdivision 18 of § 4 of the Multiple Dwelling Law, shall be heated by a heater placed in such room or in an adjoining room which connects with it except that a room whose exterior walls are exposed only on a fully enclosed inner court may be heated by a heater located one room removed from such room. For this purpose, an inner court shall be considered fully enclosed even though some of the enclosure walls are located on an adjoining lot. The aggregate input capacity of the heater or heaters installed in any apartment shall not be less than the number of living room times ten thousand (10,000) British thermal units per hour.
(b) Notwithstanding the provisions of subdivision (a) of this section, there shall be installed and continuously maintained by the owner in each apartment gas-fueled heaters in such numbers and at such locations as shall be sufficient to heat such apartment to the minimum temperature which would be required to be maintained therein by the owner under the provisions of the Health Code of the city relating to the heating of buildings, if such owner were required to furnish centrally supplied heat in such apartment.
(c) The requirements of subdivision (a) and (b) of this section are not applicable when an apartment in a multiple dwelling is heated by gas-fueled space heater or heaters which were installed by a tenant prior to December 18, 1957, and in a one or two family dwelling prior to October 1, 1964 and owned by such tenant or successor tenant.