Dave,
Sorry about the delay.
You can use a crankcase vent kit, Cat and Cummins both offer the kit depending on the engine. They are used on Natural Gas engines more than anything else. I have one for cummins, it is a fleetfuard number CV 50125 for the NG version of my engine.
BUT ...
As I mentioned, there is a recirculation unit that you can get. I have a fleetguard 93194 recirculator which will also work. It is used to capture the oil vapor and put it back into the engine.