I used to be a researcher in hypoxia and wanted to clarify this for folks.

The way your brain and body detect low oxygen is indirectly via the drop in pH, or increase in acidity, that high carbon dioxide causes. They call this hypercapnia. Without hypercapnia, there’s none of the pain or distress of asphyxiation because your body can’t actually detect oxygen or its displacement directly.

At 78%, nitrogen is the overwhelming majority of air you breathe.

After 1-2 breaths of 100% nitrogen, humans lose consciousness.

This is why working with inert gases is so dangerous - you’ll asphyxiate without even knowing you entered a room without enough oxygen to sustain life. Had to do a whole training to get our liquid nitrogen tank into a smaller animal isolation room for our study for this exact reason.

If I had to choose a way to die, I’d choose nitrogen displacement without question.