ASHRAE Journal - July 2020 - 25

TECHNICAL FEATURE

FIGURE 1 Conversion of a typical medical-surgical patient room to a temporary negative pressure patient room. (Left) A typical medical-surgical patient room may be quickly
converted to a negative pressure room by placing portable HEPA exhaust fan units that are exhausted through windows directly by or via ﬂexible duct through a ﬁxed window
panel. (Center) In this case, the return air grille is sealed. (Right) A digital pressure gage with audible alarm is placed outside the door.

with a compromised immune system from airborne
contagions. Due to the recent COVID-19 pandemic, the
focus of this article is on negative pressure isolation
rooms.

Problem
Here is the problem: every hospital in the United States
has only a limited number of negative pressure isolation
rooms. During a pandemic, hospitals simply do not have
enough of these rooms to handle the volume of patients.
So, what can be done? We do not yet know if COVID-19 is
an infectious disease spread through aerosols; however,
placing COVID-19 patients in a typical medical-surgical
or intensive care unit (ICU) room may contaminate sections of the hospital, possibly jeopardizing the health of
others.

Recommendations
This article summarizes our recent approach to successfully converting a large number of ICU and medicalsurgical patient rooms to makeshift negative pressure
rooms at two large, acute care hospitals in California.
These makeshift rooms were created in an incredibly short amount of time. The approach was so successful that it was shared among 15 other hospitals in
California.
An important distinction exists between a wellplanned negative pressure isolation room that meets
all of the requirements of the applicable codes versus a
makeshift negative pressure room that needs to become
operational within hours. This distinction is the reason
these makeshift rooms are identiﬁed as "negative pressure rooms" and not "isolation rooms."
A typical emergency room may be quickly converted

Top Ten Lessons Learned
Be proactive, not reactive.
Place noisy, portable HEPA exhaust fan units outside whenever possible.
Use a pressure monitor with a digital display and alarm for
each negative pressure room.
Where ﬁre-rated walls are penetrated, a ﬁre watch is
required.
Use rooms with full height walls or solid ceiling, whenever
possible, to prevent impact to adjacent rooms.
Do not use the existing return air duct system for exhaust.
Locate HEPA exhaust fan units to ensure all exhaust ductwork outside the room is under negative pressure.
Test, adjust and balance the affected patient rooms and
adjacent areas upon return to their original conditions.
Keep exhaust at least 10 ft (3 m) away from any populated
area and/or any OA intake that can return the exhaust air to
the hospital.
Communicate requirements with hospital staff.

into a negative pressure room at the time of a pandemic (Figure 1). The guidance for temporary emergency response measures in hospitals varies between
states and is impacted by hospital licensing. It is
critical to perform any work in conjunction with the
authorities having jurisdiction and to obtain approval
before starting.
For example, in California, the Ofﬁce of Statewide
Health and Planning and Development (OSHPD) takes a
more conservative approach than some of the national

Frank Shadpour, P.E., is the founder and president, and Stefanie Johnson is an associate principal at SC Engineers, San Diego.
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ASHRAE Journal - July 2020

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