crankcase vent
back in the old days, it was common to see them on all kinds of engines. 18 wheelers often had them as well; although much bigger, when the engine was idling you could usually find the vent tube (aka road draft tube) venting a little steam. Every once in a while we'd get one at work that would dump a quart or two of oil out of the tube in the time it took to unload their loads.
When you get a lot of air coming out of it, and/or oil, that means that combustion gases are getting past the piston. That's almost always due to worn cylinders and/or rings. Keeping that in mind, I've seen worse on engines that had 20 hours on them. The key takeaway is this. How the engine is maintained dictates how worn it is. There's possibility that the engine has at some point inhaled a bunch of dirt, and/or may have been overheated. Both scenarios will often result in excessive blow-by.
The newer engines ARE "recirculated". That's nice because there is no longer any oil and vapors expelled outside the engine, BUT there are downsides. You can't see it, so you don't know if the engine has any blow-by. Also probably the worst part is that manufacturers vent it back into the intake manifold; and in doing so if there is excessive blowby the engine will ingest and burn those vapors--worse yet if the machine is rolled onto it's side or upside down, they'll run on their own oil, and you cannot shut it down until it finally decides to shut itself off, either runs out of oil or suffers mechanical failure or completely blocks the intake with oil such that air cannot be ingested--usually when that happens it will also fill cylinder(s) with oil and then once righted, the owner will try to crank it back up. Bent rods are almost guaranteed.
