When your ageing your wine in a carboy and you have an airlock on top. Are you adding anything to the water in the lock? If so, it must have to be a very little bit?
If the wine has finished malolactic ferm. or has received good amount of K-meta, just plug the air trap hole up. if nothing fermenting its just an danger area for bacterial contamination. If its stil fermenting or just has a lot of sugar or lees left DONT. Unless youre a fan of pipe bombs.