For processes which require better sealing of the components, for example when transporting aggressive or toxic gases, we equip our fans with multi-chamber labyrinth seals around the shaft. Depending on the operating conditions and the conditions of use, three- to seven-stage seals are used, which can be supported as required by the use of a sealing gas. The fan casings are, of course, welded to be gas-tight and the flanged connections use appropriate seals.