What constitutes ventilation air?

Ventilation air is defined as the air that is supplied to a building or space to ensure a healthy indoor environment. The correct choice specifies that it includes both the portion of supply air that comes from the outdoors and any treated recirculated air. This combination serves to replace stale indoor air and reduce the concentration of indoor air pollutants.

When considering this definition, outdoor air is crucial as it provides fresh oxygen and helps dilute contaminants generated within the indoor environment. Additionally, treated recirculated air ensures that the overall airflow is effectively managed, maintaining comfort and air quality within the space. The method of treatment can include filtering and conditioning the air for temperature and humidity control, making it suitable for circulation.

Other options do not accurately encapsulate the comprehensive nature of ventilation air. For instance, air solely from the indoor environment does not bring in fresh oxygen or mitigate pollutants, while air that is merely cooled by conditioning systems doesn't necessarily indicate fresh or clean air. Similarly, although air free from pollutants is ideal for health, the definition of ventilation air specifically involves the mixing of fresh and treated air, rather than solely focusing on the absence of contaminants.