Usage of phrasal verbs is pretty common.
Here it is one of them.- to PASS OUT (to lose consciousness)
Don't confuse it with "PASS AWAY"( to die)
e.g.
People passed out due to the sweltering heat.
Passengers have some seconds to put on oxygen masks not to pass out in a depressurized plane.
The plane crash-landed and all passengers and the crew passed away.
