Do not worry.
As long as fermentation is still happening CO2 is produced
and your wine willhave a layer of CO2 on top of it.
Now when fermentation ceases then you have to be carefull.
The carboy will be filled with CO2 still from the fermentation
but when the airlock might get negative (due to higher air pressure) air might get into the carboy.
This might accumulate and the CO2 in the carboy might get less and less dense and air might take over.
So when fermentation ceases best is to rack the carboy
(you should do that anyway) in a smaller carboy with no air
above the wine.