[coolman26]

Today I was transferring 30 gallons of brew.  I was purging my carboys, as I'm out of kegs, and began to think why am I doing this?  When your careful to not splash the beer, is it necessary?  Necessary may not be to correct word, maybe beneficial is correct.  I've never had oxidation problems.  You can purge for long storage with kegs, but with carboys you can really limit the head space to almost zero.   I would think the displaced O2 when filling to the top of the carboy that entrained CO2 would fill the head space.  You usually get a little ferment from rousing a little yeast.  The more I thought about it, I felt like it was just a waste of CO2.  The Imp Stout will set for a few month on the oak.  The IPA will only be in the carboy for 7 days of dry hops.  Not going to waste the CO2 next time.  Not that I use secondary much anymore.  Guess I need more kegs.

[AmandaK]

If you're not concerned about storability, then you likely don't need to worry about it.

That being said, I purge nearly everything with CO2 and transfer without splashing. Why? Because I've put this much effort into it already. Why would I cut corners on the tail end of the process just to save a tiny smidgen of CO2?

[coolman26]

The point was for a carboy that has 1/2" of head space.  Does the beer pick up oxygen when its filling in the carboy?  That was what I was asking.  Is the CO2 more important for the coverage while racking, or for the headspace after it is racked?

[kylekohlmorgen]

If you're not concerned about storability, then you likely don't need to worry about it.

That being said, I purge nearly everything with CO2 and transfer without splashing. Why? Because I've put this much effort into it already. Why would I cut corners on the tail end of the process just to save a tiny smidgen of CO2?

+1000

[hopfenundmalz]

The point was for a carboy that has 1/2" of head space.  Does the beer pick up oxygen when its filling in the carboy?  That was what I was asking.  Is the CO2 more important for the coverage while racking, or for the headspace after it is racked?

Both.

[ynotbrusum]

I have gone to greater CO2 purging and less risk of oxidation, when possible. That said, I don't keep beer long enough to worry much about it at the Homebrew level.