in the strip industrial process as shown in fig5 a or by making the entry and exits ends of the furnace sufficiently gas tight as shown in fig5 b in fig5 a the immediate interconnecting entry and exit gas tight components may be stainless steel flanges 80 and upstream or downstream components connected to the stainless steel flanges can handle supply and return of the process gas to and from the tunnel of the furnace in fig5 b the transverse entry and exit ends of the enclosure of the furnace can be made gas tight for example by use of pressure rollers 82 or pressure pads that exert sealing pressure on both sides of the strip fig3 a fig3 b and fig3 c illustrate another example of an electric induction gas sealed tunnel furnace 30 of the present invention in this example the barrier chamber is an enlarged barrier plenum 34 formed around the outer longitudinal surface of furnace enclosure 12 by joining barrier material 32 to suitable longitudinal end structural elements of enclosure 12 in this non limiting example the end structural elements are u201c u u201d shaped entry and exit end flanges 12 a that are suitably connected to.