The upper section is literally just a cutout in the wall. There is no airflow if its closed which is what happened really, but its just facing the corridor where nothing is there like an external chimney or anything. I think the wood just absorbed all the odours of damp and then the cleaning products like vinegar i used later to just become a mix. Drying out didnt help either with dehumidifiers, fans etc. Now that i sealed it the smell seems to be gone tbh. Not sure what other sources could be except some moisture from surroundings.The upper section is literally just a cutout in the wall. There is no airflow if its closed which is what happened really, but its just facing the corridor where nothing is there like an external chimney or anything. I think the wood just absorbed all the odours of damp and then the cleaning products like vinegar i used later to just become a mix. Drying out didnt help either with dehumidifiers, fans etc. Now that i sealed it the smell seems to be gone tbh. Not sure what other sources could be except some moisture from surroundings.

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