People sometimes say that the room they are in is airless. This is a figure of speech.
If the room was truly airless and they had been there for a while they wouldn’t say anything at all. However, their loved ones would be saying things like, “he was so young,” “what a way to go,” “rumor has it that his wife locked him in the room and sucked the air out with a straw for the insurance money,” and “I hope to hell I’m in his will.”
Rather than being used to say that a space is truly without air, airless is usually intended to mean stuffy or without any movement of air. There’s a big difference, particularly if you value your life.