Negative pressure rooms are sometimes referred to as source isolation rooms, while positive pressure rooms are sometime called protective isolation rooms. Explain the thinking behind these names.

Negative pressure rooms are sometimes referred to as source isolation rooms because they prevent potentially contaminated air to exit the room.

Positive pressure rooms are also known as protective isolation rooms because they prevent the entering of any pathogen in the air to the room where a patient with a compromised immune system is staying.

Explanation:

Negative pressure rooms or source isolation rooms have lower pressure than the outside. Due to this pressure difference, air can enter the place but can not leave it, trapping the pathogens. Patients with infectious conditions are in these rooms to prevent the spreading of the disease. That is why they are also called source isolation rooms. These rooms have a  system that filtrates and circulates the air.

On the other hand, in positive pressure rooms, the air pressure is higher. As a result, the air, with any potential bacteria, virus, or particles, leaves the room to keep the patient safe. They are also known as protective isolation rooms because patients with a compromised immune system are there to protect them from any pathogens in the air.