When breathing through your mouth is helpful. A case of gas gangrene:
This is what this room smelled like. His foot had an ulcer that was completely black with dark reddish streaks going partially up his shin. Purulence oozed out. When you palpated his shin, it made the sound of rice crispies popping. Not a good sound when it comes from your leg.
(via WhiteCoat Rants, thanks for the plug btw)