How is it inefficient? I'm not saying I don't believe it, just curious. It seems like it would be a time / flow rate based scenario with constant mixing and dilution. Kinda like the purge and release method but continuous. Has anyone quantified it?
Edit: If you think about it, the method I'm describing is identical to the purge and release method in terms of volume of gas required, just less hassle because it's continuous. However, after calculating the actual amount of volume required which is over 100 gal of CO2 at atmospheric pressure, I'd hazard a guess that I am nowhere near 0 ppm O2 as I only do it for the 30-40 seconds mentioned above. There's no way it's at that high of a flow rate.