Section 19A(4) in The West Bengal Factories Rules, 1958
(4)In every factory the amount the ventilation opening in a work room below the caves shall, except where mechanical means, if ventilation as required by sub-rule (3) are provided, be of an aggregate area of not less than 15% of the floor area and shall be so located as to afford a continued supply of fresh air :Provided that the Chief Inspector may relax the requirement as aforesaid if he is satisfied that having regard to the location of the factory. orientation of the workroom, prevailing wind, roof height and the nature of manufacturing process carried on, sufficient supply of fresh air into the workroom is afforded during most part of the working time :Provided further that such requirement shall not apply in respect of workrooms of factories -(i)covered by section 15 of the Act ; or(ii)in which temperature and humidity are controlled by refrigeration.
