ASHRAE Journal - November 2019 - 44

ASHRAE - CELEBRATING 125 YEARS

ASHRAE RESEARCH

ASHRAE has also funded several research projects related to
cleanrooms over the years.

RP-202 Ventilation Requirements in Operating Rooms
Hospital operating rooms must meet one of the most complex set of control requirements of any indoor environment, if acceptable performance is to be achieved.
The overall objective of this research project was to identify and demonstrate control
strategies that could reduce energy requirements while not producing deleterious
effects on the environmental quality within the operating room.
The objective was achieved through an extensive literature search in which more
than 1,400 citations were referenced, through the development of mathematical and
biophysical models, and through analysis of data obtained in two existing operating
rooms with different system performance characteristics. Principal Investigator:
Woods, J.E., Iowa State University; Publish Date: January 1984

RP-652 Optimum Airflow Velocity in Cleanrooms
Findings from the research show that nominal airflow velocities as low as 60
fpm (0.3 m/s) are possible without a loss of cleanliness for specific work sites in
the cleanroom. Cross contamination between adjacent workspace on the cleanroom
bench was found not to be a significant problem. However, the room airflow rate
required depends on the room configuration as well as the location and strength
of the source of contamination. Therefore, a nominal velocity of 60 fpm (0.3 m/s)
may not be appropriate for all cleanrooms. Principal Investigator: Iowa State
University; Publish Date: October 1994

RP-1344 Cleanroom Pressurization Strategy Update-Quantification and
Validation of Minimum Pressure Differentials for Basic Configurations
and Applications
The research illustrated that room air leakage rate is a critical variable in determining the room "flow offset" value. Particle migration from a less-clean room into
a cleanroom is not only driven by pressure differential, but also by particle concentration differential in a form of mass diffusion. The recommendations included a
"Minimum Pressure Differential (PD) Requirements Across Cleanroom Envelope"
humidity, etc. Anesthesia gas use in surgery was commonplace, such that air-conditioning engineers and
medical professionals were concerned with controlling
the atmosphere in operating suites due to the explosive nature of the anesthesia gases. One of the earliest
publications of suggested air change rates in hospitals
was published in the 1938 ASHVE Guidebook: "Copious
ventilation, from 6 to 12 air changes per hour, is necessary to preclude accumulation of explosive mixtures and
to reduce the concentration of anesthetics to below the
physiologic threshold so that the surgeon and his personnel will not be affected.8,9
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table grouped by cleanliness class difference. Principal Investigator: Wei Sun,
P.E.; Keith B. Flyzik; John Mitchell; Aashish Watave; Publish Date: October 2011

RP-1431 Analysis of Transient Characteristics, Effectiveness, and
Optimization of Cleanroom Airlocks
A cleanroom airlock is a transitional space that has two doors in series to
separate cleanroom and corridor which often have different air cleanliness and pressures. An airlock performs as a particle, microbial or chemical fume contaminant
barrier by minimizing contaminated air to flow into a protective area. To study the
performance and transient nature of airlock, especially when a door is in motionduring opening and closing, a new terminology called Contamination Ratio (CR) was
mathematically defined which can be used to quantify a relative contamination level
from contaminated area into protective area across a barrier such as a single door
or an airlock. The research has also analyzed the scenarios between the "walk-in"
and "walk-out" by people, and between the "push-door-in" and "pull-door-out,"
in terms of particle transmissions. A recommendation table of airlock application
has been also included in the report. Principal Investigator: Wei Sun, P.E.; Keith B.
Flyzik; John Mitchell; Aashish Watave; Publish Date: October 2011

RP-1399 Survey of Particle Production Rates from Process Activities in
Pharmaceutical and Biological Cleanrooms
The aim of this research project was to understand particle sizes and the
rates of particle generation for representative processes in pharmaceutical and
biotechnological cleanrooms. This was achieved via field measurements and
data collection in several pharmaceutical and biotechnology cleanrooms. Field
measurements were performed using certified and calibrated particle counters
and airflow meters. The airflow data, particle data, and cleanroom air conditions
were recorded for both 'operational' and 'at rest' conditions to deduce the particle
generation rate. Principal Investigator: Li Song; Oluwaseyi T. Ogunsola; Junke
Wang; Publish Date: June 2018

Ongoing Research
RP-1604, Demand-Based Control for Cleanrooms, is examining this
concept and collecting qualitative data on the effectiveness of the use
of demand controlled filtration.
In 1946 Robert Bourdillon and Dr. Leonard Colebrook
showed that sepsis of burns and wounds could be caused
by bacterial contamination from the air and that welldesigned ventilation equipment could play a large part
in preventing this. Additional work on the design of
surgical suites was conducted in the 1950s on plenum
ventilation and the use of designed inlet and outlet room
conditions.10
Disturbed by the large amount of septic cases and
postoperative infections, hip-replacement surgeon John
Charnley began investigating new methods of operating
room ventilation. Building upon the work of Bourdillon

ASHRAE Journal - November 2019

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