From: Rabbi Moshe Sofer
To: Rabbi Yosef Moshe
A mistress accidentally pours petroleum instead of brandy into an unconscious maidservant's mouth while trying to revive her, causing fatal burns. The Chasam Sofer rules she is fully exempt from exile, both as one performing a life-saving mitzvah and as a case of extreme inadvertent action (misasek).
Source: Shu"t Chasam Sofer OC §177