The PCs have made an excursion to Akiton, and we ran into a question about the Breath Control Feat. Essentially, we're having trouble determining whether Breath Control can be used to mitigate the penalties of not being acclimated to thin atmosphere. Akiton's atmosphere is indicated as "breathable but thin." See the Breath Control feat:
Player Core pg. 253 wrote:
You can breathe even in hazardous or sparse air. You can hold your breath for 25 times as long as usual before suffocating. You gain a +1 circumstance bonus to saving throws against inhaled threats, such as inhaled poisons, and if you roll a success on such a saving throw, you get a critical success instead.
The mechanical benefits only refer to situations where you're actively holding your breath. However, the first line of the feat says you can breathe in "sparse air". This implies additional, non-mechanical resistance to atmospheric effects. The description of Akiton's atmosphere continues:
So, is Breath Control limited to intentionally holding one's breath, or could it be used in lieu of acclimation in environments with thin atmosphere?