So I am cold crashing for the first time , and the airlock is moving in reverse sucking air back into the carboy. I understand the physics of it but don't like it. It is obviously sucking air with O2 back into my carboy. I suppose since CO2 is heavier than air, there will still be a blanket of CO2 over the beer to stop oxidation but it feels wrong. Any opinion/experience out there. Should I have done something else?