TAB Journal Summer 2019 - 2

Tim Mahoney, TBE
Mechanical Test and Balance Corporation

SURGERY SUITE SPACE
PRESSURIZATION

A

local hospital recently completed a new surgical wing,
which consisted of the upper floor being the surgery
suite and the lower level being the sterile processing
and the decontamination area. The surgery suite was made up
of 11 operating rooms (OR), a sterile core in the middle and a
clean corridor around the perimeter (see the diagram below).

OR 11

OR 1

OR 10
OR 9

OR 3

OR 8

OR 4

Clean
Corridor

2

OR 2

Sterile
Clean Core

OR 7

OR 6

OR 5

The upper floor was served by a dedicated air handling unit
(AHU) consisting of three supply fans and four return fans.
Each OR was served by one supply variable air volume (VAV)
box and one return VAV box. Each OR was designed to
operate with an offset between the supply and return of 300
cubic feet per minute (CFM). The sterile core was served by
multiple supply VAV boxes and multiple return VAV
boxes, with a neutral offset. These offsets were
intended to maintain a minimum positive pressure
in each OR of +.020 in. water column (w.c.) to the
clean corridor and +.010 in. w.c. to the sterile core.
This leaves the sterile core +.010 in. w.c. to the
clean corridor.

Clean
Corridor

During the TAB procedures, it was determined that
the 300 CFM offset for each OR was not capable
of maintaining the required space pressures. An
average offset of 700 CFM was required to achieve
the desired pressures. This increased offset was
due to the excessive leakage under the doors. This
increased the minimum outside air (OA) on the AHU
by 4,400 CFM (see the schedule on the facing page).
This increased OA was determined to be excessive
for the cooling and heating coil capacities of the
AHU, which would cause temperature and humidity
problems in the ORs.

TAB Journal Summer 2019



TAB Journal Summer 2019

Table of Contents for the Digital Edition of TAB Journal Summer 2019

TAB Journal Summer 2019 - Cover1
TAB Journal Summer 2019 - Cover2
TAB Journal Summer 2019 - 1
TAB Journal Summer 2019 - 2
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TAB Journal Summer 2019 - Cover3
TAB Journal Summer 2019 - Cover4
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