Negative Pressure Room - Deployment Guidelines - Modtruss

Negative Pressure Rooms Stop the Spread.

In this guide, we will give an overview of negative pressure room requirements and deployment strategies. A negative pressure room is a room with lower air pressure inside the room relative to the outside. This is achieved by fitting a sealed room with an exhaust system, often including a high-efficiency particulate air (HEPA) filter to a sealed room.

The CDC recommends these specialized rooms for containment of airborne infections in hospitals. In this regard, a contagious patient can be placed inside a negative pressure room to prevent the infection from spreading to other patients in the hospital. As such, doors to the room should be closed except when entering or leaving the room, and entry and exit should be minimized. Using sensors and/or gauges, facilities should monitor and document the proper negative pressure function of the room.

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Negative Pressure Room Design

When a negative pressure room is used in conjunction with an anteroom, it is especially important that air flow from the external environment into the anteroom and from the anteroom into the isolation room. Therefore, the exhaust airflow must exceed the supply airflow by at least 30%.

Furthermore, the room must undergo a minimum of 12 air changes per hour. There should be a small air intake located on the ceiling above the foot of the patient’s bed, and an exhaust outlet leading to an air filter located above the head of the bed.

Detailed design specifications are defined by ASHRAE Standard 170-2017.

Negative Pressure Rooms and COVID-19

Negative pressure rooms are a valuable weapon in the fight against COVID-19. In general, they should be used for any patient with an infectious disease. However, during an epidemic, that may not be possible. Therefore, the CDC recommends reserving negative pressure rooms for patients undergoing aerosol-generating procedures.

Positive Pressure Rooms: Protecting the Most Vulnerable from Infection

A positive pressure room helps protect immunocompromised patients from infectious disease. In concept, it is similar to the negative pressure room, with some minor differences in design and usage outlined below. Similar precautions should be taken as with a negative pressure room. Doors should be kept closed except when entering or exiting, which should be kept to a minimum to avoid cross-contamination.

Positive Pressure Room Design

The CDC offers useful criteria for positive pressure room design:

Positive Pressure Room Negative Pressure Room
Pressure differentials > +2.5 Pa (0.01″ water gauge) > −2.5 Pa (0.01″ water gauge)
Air changes per hour >12 ≥12 (for renovation or new construction)
Filtration efficiency
  • Supply: 99.97% @ 0.3 μm DOP (dioctylphthalate particles of 0.3 μm diameter)
  • Return: none required (If the patient requires both PE and AII, return air should be HEPA-filtered or otherwise exhausted to the outside)
  • Supply: 90% (dust spot test) Return: 99.97% @ 0.3 μm DOP (dioctylphthalate particles of 0.3 μm diameter);
  • HEPA filtration of exhaust air from AII rooms should not be required, providing that the exhaust is properly located to prevent re-entry into the building.
Room airflow direction Out to the adjacent area In to the room
Clean-to-dirty airflow in room Away from the patient (high-risk patient, immunosuppressed patient) Towards the patient (airborne disease patient)
Ideal pressure differential > + 8 Pa > −2.5 Pa


Positive Pressure Rooms and COVID-19

Now more than ever, positive pressure rooms are a critical part of hospital infrastructure. With the increased risk posed by COVID-19, positive pressure rooms are perhaps even more crucial than negative pressure rooms. Moreover, the number of infected patients is so high that there are not enough negative pressure rooms, so some are turning to positive pressure rooms as an alternative to protect their most vulnerable patients.

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