Which of the following is considered an Indoor Contaminant Control measure?

The selection of sealed ducts as an Indoor Contaminant Control measure is significant because it directly addresses the importance of maintaining indoor air quality by preventing contaminants from entering the building through the HVAC system. Sealed ducts minimize the possibility of pollutants, such as dust, allergens, and other harmful substances, being circulated throughout the indoor environment. This measure ensures that the air that occupants breathe is cleaner, which is crucial for health and comfort.

In terms of the other options, while regularly opening windows can contribute to ventilation and may help dilute indoor pollutants, it is not a controlled measure since it depends on external air quality and environmental conditions. Dust control measures are essential for maintaining cleanliness and reducing dust accumulation, but they do not specifically target the containment of contaminants at the source within the ductwork. Using non-toxic materials is a positive design choice for preventing the introduction of harmful chemicals into the interior environment, but it does not specifically address the aspects of air flow and contamination management as effectively as sealed ducts do.