What does natural ventilation refer to?

Natural ventilation specifically refers to the process by which fresh air enters a space and stale air exits, primarily driven by natural forces. One key aspect of natural ventilation is the differences in pressure and temperature that occur within and outside a building. These differences create a movement of air without the assistance of mechanical devices.

When considering the context of the correct answer, the movement of air produced by differences in weight of air columns is a fundamental principle of natural ventilation. This phenomenon, known as buoyancy or stack effect, occurs when warmer, lighter air rises and exits a building, while cooler, denser air enters from lower openings, establishing a natural flow of air. This process enhances indoor air quality and regulates temperatures without reliance on mechanical systems.

The other choices predominantly refer to mechanical methods or other forms of air movement not inherent to natural ventilation processes. In contrast, the correct choice highlights the natural physical principles (specifically weight differences related to air columns) that drive air movement in a naturally ventilated environment.