Air duct cleaning's effectiveness depends on the methods used, the cleaner's expertise, and the specific contaminants present. Professional cleaning by NADCA-certified technicians using proper equipment demonstrably reduces contaminants, improve health, and optimize HVAC operation. However, duct cleaning is not a cure-all for allergies or respiratory issues and should be part of a comprehensive indoor air quality management plan. Combined with these practices, cleaning can effectively enhance indoor air quality.