It is possible to cover the whole scroll with stone wool to reduce the surface temperature of the fan or even to reduce the propagated noise. The semi-rigid bio-soluble stone wool board (compliant with Note Q of Directive 97/69/EC) consists of mineral wool obtained from melting and spinning natural rocks. This application is recommended for working temperatures above 300°C and is available in different stone wool thicknesses: 60 mm is the thickness of wool in standard insulation. Other thicknesses are available: 80 mm - 100 mm - 120 mm.