A major source of pollution in a building is?

The correct choice highlights that people are a major source of pollution within buildings. Human activities contribute significantly to indoor air quality issues through various means. For instance, everyday actions such as cooking, personal grooming, and even breathing release particulate matter, volatile organic compounds (VOCs), and other pollutants into the air. Additionally, people can introduce outdoor pollutants into indoor environments, worsening air quality.

While HVAC systems, construction materials, and cleaning agents can also contribute to indoor air pollution, it is the collective activities of the occupants that typically have the most considerable cumulative impact. Understanding that human presence and behavior can significantly affect air quality is crucial when addressing indoor pollution sources and implementing effective air filtration and ventilation strategies to enhance occupant health and comfort.