Which of the following is a common source of indoor air pollutants?

VOCs, or volatile organic compounds, are indeed a common source of indoor air pollutants, making them a significant concern in indoor environments. These compounds are often released into the air from a variety of household products, including paints, varnishes, cleaning agents, air fresheners, and even some building materials. The process of off-gassing can lead to elevated concentrations of these pollutants indoors, which may contribute to various health issues such as respiratory problems, headaches, and other symptoms commonly associated with chemical exposure.

In contrast, natural sunlight typically does not contribute to indoor air pollution; rather, it can help to reduce certain pollutants and improve air quality by promoting ventilation and the breakdown of harmful substances. Fresh air from outside is generally associated with improving indoor air quality, as it helps to dilute indoor pollutants and bring in oxygen. Properly maintained HVAC systems can also enhance air quality by filtering out particulates and managing humidity, which is essential for minimizing mold and other allergens. Therefore, among the options presented, VOCs from paints and cleaning products stand out as a prevalent source of indoor air pollution.