Negative Pressure vs Positive Pressure
Negative pressure rooms are designed to contain airborne pollutants or contaminants, such as viruses, within that particular space. In these rooms, air pressure is lowered below that of adjacent rooms and areas. This tactic keeps air from escaping the room, thus securing the rest of the surroundings.
In your search, you may have come across positive pressure rooms as well. What is a positive pressure room? This particular room has higher air pressure than surrounding rooms to filter air out, but not let it back in.
The primary use for these is for emergency medical services, but these types of modular rooms go beyond the medical field.