Which best describes the air flow in a room with positive air pressure?

The flow of air in a room with positive air pressure is characterized by the movement of air from areas of higher pressure to areas of lower pressure. In this scenario, the air flows out from the Primary Engineering Control (PEC) to the Secondary Engineering Control (SEC). This is crucial in controlled environments, such as hospitals and pharmacies, where maintaining a sterile environment is necessary.

When a space is under positive pressure, it indicates that the air inside the room is greater than the air pressure outside. This controlled air flow helps in preventing the ingress of contaminants from adjacent areas. In this setting, the air that is expelled from the PEC, which often contains clean or sterile air, is crucial for maintaining the integrity of the environment where compounding or other sensitive processes occur.

The other contexts of airflow, such as air flowing in from the outside environment or being static, do not accurately describe the dynamics of positive pressure rooms. Additionally, while filtering air before entry is important in many settings, it is not a defining characteristic of air flow in a positively pressurized room.