There are several techniques to pressurize an anteroom in healthcare and laboratory applications. When anterooms are present, such as those used for isolation rooms and pharmacies, it is not always clear how the anteroom should be pressurized in relation to the adjoining room and hallway.
Airborne Infection Isolation (AII) patient rooms are designed for negative pressure with respect to the anteroom and hallway. The anteroom can be either negative or positive to the hallway, and still ensure negative pressure in the patient room itself. The intended use of the room is key to deciding when each scenario is applied.
- An anteroom that is negative to the hallway and positive to the patient room represents cascading pressurized zones, where directional airflow comes from the hallway into the anteroom, and then again from the anteroom into the patient room. This is most common for AII rooms, where the intended use is to protect the staff and normal patient care areas from infectious agents.
- An anteroom that is positive to the hallway and positive to the patient room still enables the patient room itself to be negative to its adjoining space, but only the anteroom in this case. When the anteroom is positive to the hallway, it protects an infectious patient who may also be immunocompromised. This is less common, but it is a room pressure scenario that keeps additional airborne contaminants in the unclean hallway from threatening the patient.
In either case, to pressurize an anteroom, it is best to be achieved with a supply airflow device such as a VAV box or venturi valve. An exhaust device is usually not necessary in an anteroom (depending on its size), where a simple balancing damper can achieve accurate and reliable exhaust airflow when connected to the patient room exhaust.