ASHRAE Journal - July 2020 - 28

TECHNICAL FEATURE

existing windows if
FIGURE 2 Layout of a typical makeshift negative pressure patient room.
they are operable.
Note, the 10 ft (3 m)
Supply Air (SA) Duct
requirement is an
OSHPD temporary
Ceiling
measure and not reflective of Standard 170
SA Diffuser Constant Flow -
Makeshift Negative
Do Not Modify Existing cfm
requirements, which
Pressure Patient Room
Digital Differential
may be enforced in
Pressure Monitor with
Display and Audible Alarm -
other jurisdictions.
Set at 0.01 in. w.c.
Patient
Nurse
* The maximum airTemperature Sensor
T
flow rate from the corFloor
ridor into the room is
listed as 75 cfm (35 L/s)
Set Room Airflow Approx. 75 cfm
Negative
to Adjacent Corridor with
under PIN-4; however,
Minimum 0.01 in. w.c. Negative Pressure
in our experience, this
is not always sufficient
to maintain the required negative
made significant modifications that
pressure. For some of the rooms, the did not follow established guidelines
required cfm was greater.
and ended up making the situation
* Rebalancing the affected areas
worse.
is recommended.
Often, the hospital's maintenance
Figure 2 demonstrates the layout of
staff was eager to act by modifying
a typical room.
HVAC equipment control sequences
Each modified space should be
or constructing infection barrireviewed by a licensed engineer
ers without a properly engineered
and a one-page report should
action plan. Action without a plan
be prepared for each space to
and full understanding of the codes,
document the modifications. Each
regulations and hospital licensing
report should be dated, signed and
requirements may result in undesirforwarded to the authority havable outcomes.
ing jurisdiction and the hospital.
Lesson Learned 2: Place Noisy, Portable HEPA
The hospital's licensing personnel
Exhaust Fan Units Outside Whenever Possible
should file the report with the State
OSHPD PIN-4 recommends placDepartment of Public Health to
ing HEPA exhaust fan units inside
obtain approval for use.
the patient room. Initially, we did
Top Ten Lessons Learned
this, but soon realized it may not
The Top Ten Lessons Learned from be a good idea due to the noise levthis experience are as follows:
els generated by some of the HEPA
exhaust fan units.
Lesson 1: Be Proactive, Not Reactive
These units have a control knob,
"Don't do something just to do
which patients may feel inclined to
something," said Joel Sanders,
adjust to lower the speed or turn off
OSHPD Compliance Officer. Some
the unit altogether to reduce noise
of the facilities we visited went
levels. Building codes and regulathrough a great deal of effort and
tions recommend sound levels of 30
28

ASHRAE JOURNAL

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J U LY 2 0 2 0

Return Air (RA) Duct

Secure and Seal RA Grille (0 cfm)
Exterior Wall
Exhaust Air (EA)
Flex Duct - Terminate 10 ft
Away from Any Air Intake
Exterior Window
TE

HEPA Filtered Exhaust Unit

Electric Cord - Plug In

PHOTO 1 Place noisy, portable HEPA exhaust fan
units outside, whenever possible (Lesson 2).

dB(A) to 35 dB(A) for patient rooms.
Higher sound levels in patient
rooms interfere with the healing
process and activities of hospital
staff.
Joel Sanders, OSHPD Compliance
Officer, recommends that "whenever possible, locate HEPA exhaust
fan units outside and protect them
from the weather." The option of
placing HEPA exhaust fan units
outside (Photo 1) is more conducive

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ASHRAE Journal - July 2020

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