Section 118(7) in West Bengal Municipal (Building) Rules, 2007
(7)Every staircase shall be lighted and ventilated from an open air space of depth (measured horizontally) not less than,(i)3 m (10 ft) in case of ground and one upper floor structure;(ii)4 m (15 ft) in case of ground and two upper floor structures;(iii)6 m (20 ft) in case of further higher structures :Provided that the lighting area shall be not less than 1 m2 (10 sq. ft) per floor.Note. Every staircase shall be ventilated properly.
