However, the damp odor suggests the mold growth might be more extensive inside the ductwork or the AC unit itself, which you cannot see or properly clean. Surface cleaning won’t address this hidden source. In such cases, a professional inspection is strongly recommended to assess the full extent. They use tools like borescopes to inspect inside ducts and can identify if the evaporator coil or drip pan is contaminated.

Professional remediation is also advised if the mold returns quickly after cleaning, if there are occupants with asthma or allergies, or if the building has a history of water leaks. For verifiable results, look for a provider that offers before-and-after testing from an accredited microbiology lab to confirm the species and that the environment has been returned to a normal fungal ecology.