Enclosure fans built according to a diagonal, rather than axial or radial, principle have a flat design similar to axial fans. The blades of the fan are shaped so that they expel the air to the outside diagonally. This way, diagonal fans have a steeper characteristic curve and a higher pressure resistance. This results in a greater pressure stability and – when installed under operating conditions – a constantly high performance over a wide range of curves. TopTherm units from Rittal Systems provide this capability.