An inhaler was a medical device used by asthmatics.
Both Tom Osgood (COMIC: The Heralds of Destruction) and Petronella Osgood had an inhaler which they had to use when they became scared or excited. (TV: The Day of the Doctor, Death in Heaven)
Petronella Osgood once used her inhaler as a weapon, against a version of herself from a parallel universe. (AUDIO: False Negative)