Among the following, which factor is critical for ensuring good Indoor Air Quality (IAQ)?

Regular maintenance of HVAC systems is critical for ensuring good Indoor Air Quality (IAQ) because these systems are responsible for regulating temperature, humidity, and air circulation within a building. Proper maintenance includes changing filters, cleaning ducts, and ensuring that the systems are functioning efficiently. When HVAC systems are well-maintained, they can effectively remove pollutants, control humidity levels, and deliver clean air throughout the indoor environment. This minimizes the presence of allergens, dust, and other contaminants, significantly improving overall air quality.

The other factors mentioned can negatively impact IAQ or are not beneficial in maintaining good air quality. High indoor humidity can lead to mold growth and dust mites, which can exacerbate respiratory issues. Frequent use of chemical cleaners can introduce volatile organic compounds (VOCs) and other harmful chemicals into the air, reducing air quality. Minimizing the use of natural materials, on the other hand, doesn't necessarily improve air quality, as many natural materials can be beneficial and have better air quality characteristics than synthetic alternatives. Therefore, maintaining HVAC systems is a proactive approach to ensuring a healthy indoor environment.