When the fermentation is really going I like to stick my head really
close to the top of the must and inhale until I almost pass out.
Firstly, I love the smell of fermentation and I suggest you experience
it also and secondly, if you almost pass out that meansa there is
plenty of CO2 protecting the wine so you don't have to worry. Actually,
I use this test everyday and decide to rack to secondary based on my
smell tests. I know most won't recommend that technique , but it works
for me. Never had a wine oxidize yet.

Bob