It could be the OSV(?). To check if its faulty, start the car and let the idle stabilise, then pull out the engine oil dipstick, if you hear a slight suction noise and the idle changes, you'll need to get it changed over. I am sure that there will be other more experienced people that can give you more advice and pointers on this. Good luck.
Does the car run ok ? as Brett has said it could well be the PCV valve, indications of failure are as Brett has said dipstick slurp but they do slurp slightly so it has to be a quite audible slurp sound, smoke from the exhaust on start up this doesn't last long best to get somebody to look while you start up, lumpy idle at cold also check over all the engine for leaks especially the sump and oil filter lines from the housing.
I have seen many well maintained and healthy bimmer engines use up to a quart of oil every 1000miles, and this is considered my many BMW gurus as "normal".
As well, I have seen some that do not consume much of oil either.
If you are in doubt about ur oil consumption... then do a tune up and do a compression check. Compression readings will provide some proof as to whether your engine using more oil than it should.(if compression readings turn out normal... you have not much to worry about).