Crankcase becomes positive from excessive blowby and it needs to vent. The EPA way of doing this is with venting back into the intake so that you burn the oil with the following combustion cycles. Venting to the atmosphere is in no way detrimental to your car. particluates in the "blowby" are not going to "float around" in the air to get pulled out by the PCV, the particles would fall into the oil, or if they even were capable of being "as light as air" to float, they would get caught by the numerous baffles and openings and fall back into the oil. It is simply impossible to have "cleaner oil" with a PCV system in or out.
