How to treat black spots from AC leak myself?« Back to Previous Page

Black spots from an AC leak indicate active mould growth, which is common here due to our high humidity. The wall is likely still damp inside, feeding the mould. Your priority is to stop the moisture source and dry the area completely.

First, address the AC unit's leak—this is the root cause. Common issues here are a clogged condensate drain line or a misaligned drain pan. Until that's fixed, the problem will recur. Dry the visible moisture with a wet vacuum and increase airflow to the area with fans; a dehumidifier is highly recommended to pull moisture from the wall cavity, which can take several days.

For the mould itself, wear an N95 mask and gloves. Do not dry brush it, as this releases spores. Instead, lightly mist the spots with a diluted white vinegar solution or a detergent-and-water mix to dampen them, then scrub with a disposable cloth. Dispose of the cloth immediately in a sealed bag.

Be aware that what you see is often just the surface growth. The mould can penetrate deep into porous materials like drywall and carpet backing. If the spots return after cleaning or the area is larger than a square foot, the material is likely compromised and requires professional assessment and removal. In Dubai's climate, incomplete remediation leads to rapid regrowth. A proper inspection with moisture meters can determine the full extent of damage behind the wall.