The effectiveness of a non-contact seal depends, in principle, on the sealing action of the narrow gap between the shaft and housing. The gap may be arranged radially, axially or in combination (fig. 1). These seals can be as simple as a gap-type radial shaft seal or more complex, like a labyrinth seal. In either case, because there is no contact, these seals generate almost no friction and do not wear. They are not easily damaged by solid contaminants and are particularly well suited for high speeds and high temperatures.