Indoor air quality (IAQIndoor air quality. Healthfulness of an interior environment; IAQ is affected by such factors as moisture and mold, emissions of volatile organic compounds from paints and finishes, formaldehyde emissions from cabinets, and ventilation effectiveness.) is a big deal. It doesn't get nearly as much attention as energy efficiency or green building programs, but it should be one of the highest priorities for anyone who breathes air and spends time indoors.
It's actually part of an even bigger deal called indoor environmental quality (IEQ), but I'm just going to focus on IAQ here as I show you four ways your ducts might be hurting your indoor air quality.