(iii)single or multicored insulated cables accommodated in solid drawn heavy gauge screwed galvanised conduits used in conjunction with approved flame-proof fittings, the conduit being sealed at both ends and installed in such a manner as to permit internal condensation to drain to a point or points from which it may be removed; where a conduit runs from a zone "1" area to zone "2" area or an area which is not hazardous area, an adequate seal shall be provided outside the boundary of zone "1" area;