The thermal insulation lagging is made using mineral wool and aluminium plates placed around the casing of some fans.

A fan can be provided with an insulation lagging to avoid two possible problems:

- When the fan conveys hot gases, the casing also warms up, frequently reaching the temperature of the gases within. This makes the casing metal to become a risk for people since it can cause severe burns. To avoid this danger and reduce the heat emission, the insulation lagging is installed allowing a reasonable temperature outside the fan.

- When the fan noise level is higher than allowed, apart from using silencers, an insulation lagging can be installed around the fan casing to muffle the noise and prevent people from having sound perception problems when staying near the fan.