Now I don't know about anyone else, but when I breathe through my mouth, I generally taste, to some extent, whatever aroma is floating through the air at a given moment. Not exactly the best time to be in a room with freshly killed specimens and specimens fixed in formalin. Let me interject that I don't really mind the smell of formalin. It's not a pleasant smell, but it doesn't turn my stomach.
However. Breathing in through the nose, which has a filter system, and breathing in through the mouth, which has TASTE BUDS, are two completely different animals (no pun intended).
I still don't know how I survived those two hours.