108.Recirculation of air: Any air recirculation system shall be designed so that:
(1) the concentration of dusts, fumes, gases, vapours and mists in any work station is lower than the weighted average exposure value permissible in the work environment and the permissible recirculation concentration provided for in Schedule I;
(2) a duct is provided for evacuating contaminated air outside the establishment in case the air filtering system breaks down or is not working properly;
(3) no dusts, fumes or mists are discharged into a room where no dusts, fumes or mists were present before the air recirculation system is put into operation; and
(4) there is no recirculation of gases, vapours, mists, fumes or dusts which are identified under Schedule I as a substance whose recirculation is prohibited.