I understand the need for a negative pressure room for isolation and airborne precaution. I have previously come across questions of the direction of air flow in these scenarios. I read examples and still get confused. Any tips on how to understand this process? Also, are positive pressure rooms used only in immunosuppressed patients?

Negative room pressure is an isolation technique used in hospitals and medical centers to prevent cross-contaminations from room to room. It includes a ventilation system that generates negative pressure to allow air to flow into the isolation room but not escape from the room, as air will naturally flow from areas with higher pressure to areas with lower pressure, thereby preventing contaminated air from escaping the room. This technique is used to isolate patients with airborne contagious diseases such as tuberculosis, measles or chickenpox.

Positive pressure is a pressure within a system that is greater than the environment that surrounds that system. Consequently if there is any leak from the positively pressured system it will egress into the surrounding environment. Hospitals may have positive pressure rooms for patients with compromised immune systems. Air will flow out of the room instead of in, so that any airborne microorganisms (e.g., bacteria) that may infect the patient are kept away.

Reference 1, Reference 2