What two conditions are required for air to move?

Air movement is primarily driven by differences in pressure, which create air flows from areas of high pressure to areas of low pressure. For air to move effectively, there must be a designated pathway for the air to flow, such as openings in a building, ducts, or natural ventilation routes. Additionally, a change in pressure is essential because this difference creates the driving force behind air movement. When the pressure in one area is higher than in another, the air naturally moves toward the lower-pressure area, facilitating circulation.

While other factors such as temperature and humidity can influence the density of air and affect overall comfort and energy efficiency, they do not directly cause air movement in the same way that pressure differentials do. Thus, the correct conditions for air movement are the presence of a path for the air to flow through and an accompanying change in pressure that initiates that movement.