If Keiji stands with a lit candle in a completely sealed room and Yuna observes from outside the room through a glass window, what happens to the candle flame when all the oxygen in the room is used up?

Make your response very short.
When all the oxygen in the sealed room is used up, the candle flame will go out because fire requires oxygen to continue burning. Without oxygen, the chemical reaction that produces the flame cannot occur, so Keiji will observe the flame extinguishing. From outside the room, Yuna will also see the flame disappear, even though she is not directly experiencing the change in the room's atmosphere.