The function of this silencer is to reduce the sound of outgoing air when the machine switches the air pressure off (for example in case you open the guarding).

The colour of the silencer indicates that there is some pollution in the air system. This can be oil, water or other pollution that should not be in the system. This can cause serious failure on all pneumatic components!

The cause can be the failure to perform regular maintenance: Is the condensate drain emptied and cleaned every week?

To define that if it is not an old problem, you have to replace the silencer (Festo UC-1/4).