The sylph inability to breathe ash is not true of every individual.

‘Ash-breathers’ represent only a very small segment of the sylph population, but are nevertheless looked upon as a threat to the moral core of sylph society. Adaptation to the environment the Celestial Heritage Conservatory considers a purgatory is itself blasphemous, and those individuals who can breathe freely in open erjan air are barred from serving in the Astral Templar, or otherwise working for the theocracy. In Llyri, an ‘ash-breather’s career options are, through no fault of their own, very limited.