V-ZUG Combi-Steam SL Operating Instructions Manual page 70

... Descaling
Durgol swiss steamer decalcifier
The descaler contains highly effective acid. Rinse away any splash-
es immediately with water. Follow the manufacturer's instructions.
70
For descaling, only use the special descaler developed for
this appliance and which is available at all good chemists.
This special descaler enables you to achieve a gentle yet
professional level of descaling.
Standard descaling solutions are not suitable as they may
contain foam-creating additives or not be effective enough.
Using a different descaler could cause:
Overfoaming in the cooking space
Insufficient descaling of the boiler
Damage to the appliance in the worst case.