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Corrosion protection

Casing of the air-handling unit (AHU) should be adopted to the environment of its installation. More aggressive environment requires higher corrosion protection of the AHU casing. This way, durability of casing over the years of AHU operation is assured.

Corrosion protection

Corrosivity categories of outdoor environment are introduced by the norm ISO 9223. Categories vary from very low (C1) to extreme (CX) atmospheric pollution. The norm says how much the environment causes corrosion of the AHU casing.


The casing of DUPLEX Flexi 3 comes with aluminium zinc protection AZ185. The outer casing is resistant in the category C4 (installation in industrial areas, coastal areas with moderate salinity). Besides Flexi 3, we also offer DUPLEX Multi units. Their outer casing has been resistant in the category C4 since 2012, in both indoor and outdoor version.

Eurovent recommendation

For AHU installed indoor and outdoor, casing with resistance in the category C3 is recommended. Resistance in the category C4 is recommended for units operating in corrosive environment.

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