In the case of a water landing, the air filter shields your CYPRES from water penetration. Its design prevents water going through, while allowing clean air. 
CYPRES Filter only needs to be changed after it has been in contact with water.
The CYPRES Filter offers waterproofness for up to 24 hours at a water depth of 2.5 metres in conjunction with the sealing of the device itself. The Filter is easy to change, just use the CYPRES Filter Changer to remove the old filter from the housing and to screw in the new one.