General:
* Claustrophobic: This is the most direct and common word for this feeling.
* Oppressive: This suggests a heavy, weighty feeling that is hard to bear.
* Stifling: This implies a lack of air or freedom, making it difficult to breathe.
* Suffocating: This is a more intense word, suggesting a feeling of being unable to breathe.
* Close: This word is more subtle, but still conveys a sense of being trapped or confined.
Descriptive:
* Airless: This word emphasizes the lack of fresh air.
* Heavy: This word evokes a sense of weight and pressure.
* Dense: This suggests a thick, impenetrable atmosphere.
* Cloying: This implies a feeling of being overwhelmed by something sweet or heavy.
Metaphorical:
* A cage: This compares the atmosphere to a physical prison.
* A tomb: This emphasizes the feeling of being trapped and unable to escape.
* A vise: This suggests a feeling of being squeezed or crushed.
The best word to use will depend on the specific context and the tone you want to convey.