Originally Posted by
Coagie
Is it possible if an aircraft still used a Halon fire suppression system, that, in the course of fighting a Lithium-Ion battery fire, that all the Halon might be emptied from the tanks and extinguishers in a futile attempt to extinguish the fire, and all the Halon expelled displaced enough oxygen aboard the aircraft, to make everyone pass out? I know in places I've worked, that employed Halon fire suppression, there was an audible alarm along with a strobe light that warned that the Halon system was about to go off, and you had a certain number of seconds to either get out or disable a false alarm, because you couldn't breathe, once the Halon came out.
It's not possible.
Halon is used for fire suppression in enclosed spaces. One of the nice features of Halon is that it is not particularly toxic (despite the alarms) and it efficiently suppresses most fires at concentrations of only ~5%. It would not be able to prevent all lithium batteries from burning, but it would prevent the fire from spreading to other materials, as long as the cargo hold remains in one piece and reasonably airtight.
In the event that the fire is so inconveniently located that it burns through the bulkheads separating the cargo hold from the passenger cabin, halon would leak through the holes and would fail as a fire suppressant, but it would not by itself kill anyone or displace oxygen anywhere.