In a hospital setting, certain populations are more vulnerable to airborne infections including immune-compromised patients, newborns and elderly people. Of course, hospital personnel and visitors can also be exposed to airborne infections as well. This is why it is important that certain rooms in a hospital have negative pressure.
Purpose of Negative Pressure Rooms
A negative pressure room in a hospital is used to contain airborne contaminants within the room. Harmful airborne pathogens include bacteria, viruses, fungi, yeasts, molds, pollens, gases, VOC’s (volatile organic compounds), small particles and chemicals are part of larger list of airborne pathogens you can find in a hospital.
Image credit: By Rrobotto - Own work, Negative air pressure CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=56580980
Isolation rooms are negatively pressurized with respect to adjacent areas to prevent airborne contaminants from drifting to other areas and contaminating patients, staff and sterile equipment.
Rooms to Negatively Pressurize
Rooms that should be negatively pressurized according to The 2014 FGI Guidelines/Standard 170-2013 include:
- ER waiting rooms
- Radiology waiting rooms
- Airborne infection isolation (AII) rooms
- Cytology, glass washing, histology, microbiology, nuclear medicine, pathology, and sterilizing laboratories
- Autopsy rooms
- Soiled workrooms or holding rooms
- Soiled or decontamination room for central medical and surgical supply
- Soiled linen and trash chute rooms
- Janitors’ closets
Negative Pressure in Isolation Rooms
A negative pressure isolation room is commonly used for patients with airborne infections. For example, a patient with active tuberculosis, a disease caused by the bacteria Mycobacterium tuberculosis, will be placed in a negatively pressurized room because the tuberculosis bacterium is spread in the air from one person to another. When the patient with active tuberculosis sneezes or coughs, other people may become infected when they inhale. However, by using a negative pressure room you can better contain the bacterium within the room.
Pathology and histology laboratories also use negative pressure to isolate odors and airborne chemicals from other areas of the hospital. Exposure to these airborne chemicals could also cause adverse health effects.
Positive pressure can be used in rooms adjacent to a negative pressure room. The purpose of positive pressure is to insure that airborne pathogens do not contaminate the patient or supplies in that room. Positive pressure could be use in an operating room to protect the patient and sterile medical and surgical supplies. Positively pressured rooms are typically considered the cleanest rooms in the hospital.
Unbalanced Pressure Checklist
To prevent unbalanced pressure, routine checks should be made. Here's a short list of where you should start...
- Monitor the supply and exhaust rates for the room.
- Check that supply and exhaust fans are operating properly.
- Check for blockages of supply diffusers and return grilles within the room; occupants may block them in an effort to improve their thermal comfort.
- Check performance of fume hoods and biological safety cabinets within the room and in adjacent rooms. Poor performance of these units affects air balance within nearby rooms.
- Monitor all pressure systems after any renovation. Renovations may alter the HVAC system in a manner that impacts the air balance among nearby rooms.
Creating Negatively and Positively Pressured Rooms
Most hospital HVAC duct systems can be reworked to accommodate special air pressures in fixed rooms. Since it can be expensive to remodel to create negatively and positively pressured rooms here are a couple germ fighting options.
The first approach is killing the pathogens, which requires a relatively high dose of ultraviolet (UV) radiation installed into HVAC systems, but the cost of this is considerable.
The other option is a commercial one. NQ Industries Inc. has developed products for medical application in contaminated environments including mobile Ultraviolet-HEPA-Carbon-Photocatalysis air purification systems.
When rooms are not properly pressurized (positive or negative), airborne contaminants can escape putting the health of patients and staff at risk. No matter what system is used, the need for negatively and positively pressured rooms in the hospital is well documented.
Mechanical Systems Handbook for Health Care Facilities
J. Robbin Barrick, PE, and Ronald G. Holdaway, PE ASHE copyright 2014.
Medical and Hospital Air Treatment NQ Industries Incorporated
Image credit: By KHSS Waiting area CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons