2N Helios IP User manual, 1510 v1.13 - Manual (Page 131)

Maintenance 4.4
131
4.4 Maintenance
A frequent use makes the device surfaces, especially the keyboard, dirty. Use a piece
of soft cloth damped with clean water to remove the dirt. You are recommended to
follow the instructions below while cleaning:
 Do not use aggressive detergents (such as sand or strong surfactants).
 Clean at dry weather to make penetrated water, if any, dry up quickly.