In relation to
0010311: All creatures rely on their mouths - drown/suffocate while only [APERTURE] breathing orifice is occupied. it is sort of obvious that there is only 1 external breathing hole more or less commonly shared between all creatures. This presents problems when the mouth is actually blocked, since if you know the uncomfortable feeling of holding your breath while pinching your nose, a lot of pressure builds up as you begin to suffocate, meanwhile you can close your mouth and breathe at the same time, DF creatures dont have this luxury.
Noses - Work a lot like mouths, things can go up your nose but importantly *most* reagents enter & leave the mouth, on creatures with them (some creatures like dogs may have a nose breathing preference) it allows them to passively recover air slightly faster even while the mouth is full. Suffocation is not impossible, and relative size of the nose can determine how much air they take in relative to the mouth, often listed as [small] on the body plans.
Gills - A fish's equivalent to a nose, outside of the mouth and often on the creatures body/head/neck, they are 'water detectors' that give immediate passive breathing when submerged in water recomputing suffocation health, it allows them to convert water into breathable air for their lungs,
this partially would help with computing when a creature has stopped air-drowning such as being placed in a aquarium.Breathing through the skin - A alternative but present on some creatures like amphibians like frogs or creatures that don't have mouths or noses without tags exclaiming otherwise, however it makes them very vunerable to air/dust contaminants they aren't immune to, could be adapted on creatures like cave blobs.
Blowholes/Cartilage-less noses - A special exception for whales and particular monsters, where the nose becomes directly unseperable but inset on the face, head or the body, skeletons for instance have no requirement to breathe but shouldn't have noses in the first place consistently.
Having a nose would allow you to compute faster when the creature breathes compared to creatures without noses undergoing suffocation health states. A comparable difference between the two's survival in different circumstances. Damaging or severing the nose affects your ability to breath co-dependently.
Yes dwarves literally are mouth breathers.