The answer to 'duct cleaning not working' is that there are several common causes for duct cleaning being ineffective, including inadequate equipment, improper techniques, and underlying duct system issues. Symptoms may include poor airflow, dust buildup, and continued indoor air quality problems.
Some solutions include using more powerful commercial-grade vacuum equipment, thoroughly cleaning all ductwork components, and addressing any structural issues with the duct system. However, more complex problems like leaky or damaged ducts may require the expertise of a professional HVAC technician to properly diagnose and repair.