Duct cleaning is only one part of indoor air quality. Start with source control: vent cooking and bathing moisture outdoors, keep combustion equipment maintained and avoid introducing strong solvents or smoke indoors.
Filtration and airflow
Use a filter the system can handle and replace it before it becomes restrictive. Higher MERV is not automatically better if the blower and duct design cannot support the pressure drop.
Humidity and ventilation
Canadian homes need balanced humidity and deliberate ventilation through bathroom fans, kitchen exhaust and compatible HRV or ERV equipment. An HVAC assessment can identify equipment hygiene issues without assuming every complaint begins in the ducts.