Wiktionary
self-rescuer
n. A self-contained device to generate oxygen for breathe.
Usage examples of "self-rescuer".
Miners had self-rescuers, and additional ones were scattered through the mine and on equipment, so the possibility existed that someone could have been swapping them out over the last thirteen hours, but.
The far end of the mine does not have a sustainable atmosphere, and we're way past the time when someone could use the self-rescuers to survive.