Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove the silencer

Observation:

The silencer could be clear or green dependent upon serial numbers.
1. Grey Silencer
Thoroughly inspect for any signs of restrictions / blockages and ensure the sponge has not deteriorated.
2. Green Silencer
Thoroughly inspect for any signs of restrictions / blockages and ensure the paddle opens and closes freely.