I think he meant PCV valve, Cixi. Positive Crankcase Ventilation valve. The manufacturers often route the blowby gasses in the crankcase area into the incoming air stream so that they will be burned by the engine, to reduce air pollution. The PCV valve insures that air from from the crankcase goes into the air intake, but fresh air does not flow in the opposite direction, bringing dust with it into the crankcase.
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