Cummins Filtration crankcase ventilation systems are innovative products that use proprietary technology to control oil leakage and crankcase emissions in diesel engines. Open crankcase ventilation systems (OCV) provide excellent filtration of aerosol crankcase emissions, a phenomenon commonly known as gas breakthrough. Gas breakthroughs are the result of high-pressure gases and oils escaping around piston rings and outlets. Oil mist attracts particles of dust and aerosol, which leads to the accumulation of pollutants, both on the engine and on the surface below it. This condition increases the amount of necessary cleaning in the engine compartment, and also leads to unpleasant oil seepage on the roads, parking lots, floors of garages and driveways.