This is the 12347th most frequent Turkish word.
havasız
"Lacking air" or "stuffy."
Here, 'havasız' means lacking air or vacuumed, used to describe the condition of the box.
Havasız bir kutu uzun süre dayanamaz.
An airless box cannot last for a long time.
In this sentence, 'havasız' is used metaphorically to describe a tense or unpleasant environment.
Son konuşmada ortam bir anda havasız oldu.
The atmosphere became tense all of a sudden during the last conversation.
The word 'havasız' describes the stuffy or airless condition of the room, indicating a lack of fresh air.