CDA FW971 Installation, Use And Maintenance Manual page 9

The salad crisper is designed with a humidity control to ensure fruit
and vegetables last longer.
This can be adjusted by the slider at the front right of the salad crisper.
Fully opening the slider control to high humidity restricts the amount
of dry air entering the crisper from the fridge compartment, extending
the life of items such as lettuce and cucumber.
Open (fully left) = Low.
Closed (fully right) = High.
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