As I remember, there are over 50+ nature codes. Maybe someone can correct the number. As I remember most are pretty simple to figure out auch as ALOC is altered level of consciousness, CP is chest pains, FALL is a fall injury, INTB it internal bleeding. Adding and A makes them an ALS call.
I guess I'm curious why someone in Tucson is so interested in the nature codes anyways as you won't be able to hear or receive those calls anyways. If you can hear RWC, they are dispatched in plain language over the air.