When highly pressurized combustion gases are blown by the piston rings and into the crankcase, this is commonly referred to as "Blow-By". This process can heavily contaminate the gases making them unfit for release into the atmosphere as a system exhaust. A Crankcase Ventilation System (CCV) routes the gases through a filtering process to purge them of oil residue and other contaminates before they are either recirculated back into the combustion process or released into the air.