The grey Sea King has the UK Mil EAPS/SNIPS (Engine Air Particle Separation/Snow and Ice Protection) system - the black screens have vortex generators that spin the air entering the chamber, centrifugal force pushes sand, ice and a lot of the salt into a collection chamber at the bottom where 2 powerful electric blowers eject it.
It works well as long as you don't push the cyclic forward harshly - on a sloping ground landing for example - as it is possible for the blades to contact the filter box.