Is someone who suffers from asthma and needs to use a nebulizer to make it easier for them to breath (not pekuach nefesh) allowed to use it on Yom Kippur? (In a way of course that it’ll be turned on for example by using a Shabbos Clock.) Is the inhaling of the mist/steam/whatever comes out considered to be like drinking or not?
From experience, the ‘mist’ inhaled through an inhaler does not condense to become liquid, so that there will not be a prohibition on using the inhalation machine on Yom Kippur. Moreover, the user can be careful not to swallow any liquid that might condense.
There are two additional reasons for leniency:
1. The action of using an inhaler is not defined as drinking, but rather as breathing. It is of course permitted to breath, and it would be permitted to breath even in a sauna, so that there is no prohibition.
2. The liquid is not water, but rather medicine, and is not fit for human consumption.
As an extra precaution, it is advisable to breath through the nose, and not the mouth – but for somebody who is sick, it is permitted even through the mouth.