While “black mould” is a common term, the specific type (like Stachybotrys) requires lab identification to confirm its potential for producing mycotoxins. However, many common moulds found in AC systems, such as Cladosporium or Aspergillus, are known to cause the exact symptoms you describe—stuffy noses, coughing, and throat irritation—especially when exposure is continuous during sleep.

For a situation like this, cleaning it yourself is not advisable. Disturbing the mould without proper containment can aerosolize a high concentration of spores, potentially worsening your exposure and spreading the problem. The priority is to stop the moisture source. You’ll need an AC technician to repair the leak first.

After the leak is fixed, a professional inspection is recommended. They can assess the extent of growth inside the wall cavity and the AC unit itself, which isn’t visible. Reputable inspectors use moisture meters and thermal cameras to find hidden dampness and can take samples for lab analysis to identify the mould species. This evidence-based approach tells you exactly what you’re dealing with and the best course for safe, effective remediation.