Scavenging is obtained by introducing a secondary flow (connecting for example to the ejector muffler) to the drop tube on the multi-cyclone block. In this way the contaminant is sucked into the exhaust stream.
The main advances of scavenging are:
Longer filter life service, resulting with higher pre-cleaner efficiency
Drop tube not just straight down but it can be located in various orientations
No servicing required (if installed only with evacuator valve and if heavy duty condition occur, can be easily serviced)