The Importance of Negative Air in Patient Isolation Rooms

As the US begins to better manage the COVID-19 pandemic and hospitals and healthcare systems prepare for a possible second wave, the conversation around the importance of negative air pressure in patient isolation rooms is more and more common.  We sat down with Norris Gearhart, CR, CCHM and President/CEO of Gearhart and Associates to better understand what negative air pressure is, how it is currently used in healthcare spaces, and the importance of negative air pressure in relation to infection control and prevention.

What is negative air pressure?

Negative room pressure or “negative air” is used to prevent cross-contamination from dirty or a potentially hazardous environment into a clean or non-contaminated environment.

How is negative air achieved? 

Negative air is achieved when the pressure in the space is lower than the surrounding areas.  Air naturally flows from areas with higher pressure to areas with lower pressure as the area with lower pressure strives to create equilibrium with the space around it. 

What are some examples of negative air rooms in a healthcare setting?

Some examples of rooms in healthcare that would use negative air pressure are isolation rooms for patients with or potentially with airborne contagious diseases such as: Tuberculosis, measles, chickenpox, Severe Acute Respiratory Syndrome (SARS-CoV), Middle East Respiratory Syndrome (MERS-CoV), Influenzas (flu), and Coronavirus Disease 2019 (COVID-19).  Other areas within healthcare that should be negatively pressurized include: 

  • Bathrooms
  • Emergency Department
  • Radiology 
  • Morgue
  • Soiled Utility Storage
  • Dirty Side Sterile Processing
  • Environmental Services Closets and Storage Areas

Are there requirements that must be met for a negative pressure room in the healthcare space?

For hospital Airborne Infectious Isolation Rooms (AIIRs) with negative-pressure differential the room needs to be well sealed to prevent excess air leakage into or out of the room.  Within reason, the tighter the room is constructed the more efficiently the air pressure differential can be maintained.  Negative pressure rooms should be designed in healthcare for a minimum CFM of airflow for 12 air changes of exhaust per hour and maintain a minimum of 0.03- inch of water column. 

Why is negative air critical to meeting ICRA Class IV requirements?

Infection Control Risk Assessment Class IV is focused on construction barriers to prevent dust and potentially dangerous pathogens from entering patient care areas.  Negative air pressure within the workspace is critical in ensuring that the air flows from “clean” undisturbed patient areas to the “dirty” work area preventing the escape of potential pathogens into the patient occupied space. While this is primarily focused on construction and renovation activities these same precautions must be considered when expanding patient care areas to accommodate a surge in COVID-19 patients.   

In relation to the current Coronavirus pandemic, how important is it for hospitals to increase the number of patient isolation rooms?

As a nation it appears that we have “flattened the curve” of this pandemic. States are working on ways to reopen business and services. It remains to be seen if the precautions taken will be enough to prevent a second wave of infections. We also don’t know the impact COVID-19 will play as we reenter the flu season coming into the fall. Hospitals need to take time now to plan for and have readily available the resources necessary to respond to the potential for an overwhelming surge in COVID-19 patients. Mobile Class IV capable containment rooms provide the flexibility to repurpose and convert existing spaces into negative pressure patient care rooms.

Isolate symptomatic patients as soon as possible. Set up separate, well-ventilated triage areas, place patients with suspected or confirmed COVID-19 in private rooms with the door closed and with private bathrooms (as possible). Reserve AIIRs for patients with COVID-19 undergoing aerosol generating procedures and for care of patients with pathogens transmitted by the airborne route (e.g., tuberculosis, measles, varicella).

When would positive air pressure be necessary?

Positive pressure isolation rooms keep contagious diseases away from patients with compromised immune systems such as those with cancer or transplants.  Other places in the hospital where you want clean HEPA filtered positive pressure air are; operating rooms, delivery rooms, procedure rooms, CATH lab, sterile storage, serology, biochemistry, pharmacy, medication room, and clean linen storage.

Is it possible to convert an existing HVAC system to 100% outside air to eliminate the risk of recirculated air? 

Infection Control Today recently published a fascinating article on large-scale conversions of specific areas in a hospital to negative air wards. These transformations are possible but can be very expensive and not timeframe optimal for older facilities. 

Is filtration a satisfactory substitute for negative air?

Filtration reduces the risk for transmitting airborne infectious agents. Depending on their size, particles may be deposited in the upper or lower respiratory tract. Particles can also be deposited in open wounds during dressing changes or invasive procedures. When used correctly, portable HEPA filters prove to be an effective method for achieving an airborne isolation environment by trapping the 

What are common hurdles or areas of concern in achieving and maintaining negative air pressure?

  • Where is the make-up air being pulled from and where is the air being exhausted
  • Existing walls/soffits
  • Egress requirements
  • NFPA 241 fire sprinkler requirements
  • Supply air leakage
  • Expansion joints
  • Sensors for variable speed fans
  • Fire dampers

STARC Systems RealWall™ and LiteBarrier™ systems are ideal for creating patient infection isolation spaces of any size. The re-configurable and cost-effective panels isolate contaminated areas and protect patients and staff from dangerous pathogens. The modular, air-tight panels exceed Class IV ICRA requirements when installed properly, can be quickly deployed, and easily cleaned with standard antimicrobial disinfectants.

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