United States Health Effects Research EPA-600 1-78-064
Environmental Protection Laboratory November 1978
Agency Research Triangle Park IMC 27711
Research and Development
«>EPA Description of the
CLEANS Human
Exposure System
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL HEALTH EFFECTS RE-
SEARCH series. This series describes projects and studies relating to the toler-
ances of man for unhealthful substances or conditions. This work is generally
assessed from a medical viewpoint, including physiological or psychological
studies. In addition to toxicology and other medical specialities, study areas in-
clude biomedical instrumentation and health research techniques utilizing ani-
mals — but always with intended application to human health measures.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/1-78-064
November 1978
DESCRIPTION OF THE CLEANS HUMAN EXPOSURE SYSTEM
Arthur A. Strong
Research Services Branch
Clinical Studies Division
Health Effects Research Laboratory
United States Environmental Protection Agency
Research Triangle Park, North Carolina 27711
U.S. Environmental Protection Agency
Health Effects Research Laboratory
Office of Research and Development
Research Triangle Park, North Carolina 27711
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DISCLAIMER
This report has been reviewed by the Health Effects Research Laboratory,
U.S. Environmental Protection Agency, and approved for publication. Mention
of trade names or commercial products does not constitute endorsement or
recommendation for use.
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FOREWORD
The many benefits of our modern, developing, industrial society
are accompanied by certain hazards. Careful assessment of the relative
risk of existing and new man-made environmental hazards is necessary
for the establishment of sound regulatory policy. These regulations
serve to enhance the quality of our environment in order to promote the
public health and welfare and the productive capacity of our Nation's
population.
The Health Effects Research Laboratory, Research Triangle Park,
co idncts a coordinated environmental health research program in toxicology,
epidemiology, and clinical studies using human volunteer subjects.
Th«se studies address problems in air pollution, non-ionizing
radiation, environmental carcinogenesis and the toxicology of pesticides
as well as other chemical pollutants. The Laboratory participates in
th? proposed, provides the data for registration of new pesticides or
proposed suspension of those already in use, conducts research on
hazardous and toxic materials, and is primarily responsible for providing
the health basis for non-ionizing radiation standards. Direct support
to the regulatory function of the Agency is provided in the form of
expert testimony and preparation of affidavits as well as expert advice
to the Administrator to assure the adequacy of health care and surveillance
of persons having suffered imminent and substantial endangerment of
their health.
The exposure system described in this document provides researchers
with a resource for the safe and precise measurement of various health
indicators that are affected by human exposure to ambient levels of air
pollutants. Precise control of the atmosphere within the exposure system
permits the simulation of the air pollutant levels found in urban areas
under known conditions. This combined with precise and reproducible
measurements of the exposure conditions and physiological parameters
provides research data necessary to establish and support environmental
standards.
F. G. Hueter, Ph. D.
Acting Director,
Health Effects Research Laboratory
m
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ABSTRACT
Legislative mandates require the Environmental Protection Agency to
determine the levels of risk to the human population exposed to air pollu-
tants and establish standards to limit that risk. Two stainless steel
Controlled Environmental Laboratories (CEL) were constructed in the EPA
Clinical Studies Laboratory Facilities in Chapel Hill, North Carolina to
determine the pulmonary and cardiovascular health problems of humans ex-
posed to ambient levels of selected air pollutants. Both gaseous and water
soluble particulate pollutants can be generated in desired concentrations
in accurately controlled air flows, temperatures, humidities, and light
levels. Each CEL operates independently of the other, and the pollutants
can be introduced either singly or in combinations. Four PDP-11/40 computers
are required to automate all control, measurement, and data acquisition for
tne CEL environment and the physiological measurements of the test subjects.
The exposure system was designed to house six test subjects for several
weeks without interruption of the exposure insult.
A brief description of the exposure laboratories and the support
systems including their functions is provided. The methodology used to
measure and control the conditions in each CEL is included along with a
lisv. of the physiological capabilities.
IV
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CONTENTS
Abstract iv
Introduction 1
Clinical Environmental Laboratories 2
Environmental System 7
Gaseous Pollutant System 10
Aerosol Pollutant System 16
Physiological Data Acquisition System 22
Computer and Peripherals 28
Information Sources Acknowledgment 30
References 31
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INTRODUCTION
One of the objectives of the Environmental Protection Agency is to set
standards for maximum acceptable environmental air pollutant levels. These
must be low enough to prevent impairment of the health and welfare of the
population and have minimal economic impact on the affected industry. If
not supported with defensible research data, regulated levels of air pollutants
will come under question as to their validity and necessity. Therefore, a
major effort of the Clinical Studies Division (CSD) of the Health Effects
Research Laboratory (HERL) is directed towards obtaining data on the subtle
health effects of selected air pollutants on volunteer human test subjects.
To provide the necessary resources, a computer automated controlled environ-
mental laboratory facility was constructed in the Chapel Hill, North Carolina
Clinical Laboratory Facility of CSD. The exposure system is identified by
the acronym CLEANS for CJinical Laboratory for ^valuation and Assessment of
Ncxious Substances.
The two controlled environmental laboratories were designed to operate
over a wide range of temperatures, humidities, and light levels with accurately
controlled pollutant levels of carbon monoxide, sulfur dioxide, nitrogen
monoxide, nitrogen dioxide, ozone, and water soluble aerosols. Each laboratory
operates independently of the other with the pollutants introduced either
si igly or in combinations. The period of exposure may last from hours to
wf. iks.
Each laboratory contains the complex physiological instrumentation to
ac uire, under computer control, the cardiovascular and pulmonary functions
of the human test subjects. All measurements are made under the supervision
of physicians and medical technicians who use the computer to rapidly
acquire, compute, and display the desired physiological measurements data
so the control console operator can determine the health status of the
subject and evaluate the general reliability of the acquired data.
The design of the CLEANS chamber was based largely on information
gathered by Dr. John H. Knelson, the CSD Director, on visits to five human
research facilities. At each, he discussed the resources, limitations, and
general problems of each facility with the responsible investigator. A
"Workshop on Controlled Environmental Chambers" held under the auspices of
the Office of Research Grants on April 26-27, 1971 provided additional
information on the general subject of controlled environmental chambers for
humans. It was concluded from the workshop that the five human environmental
chambers visited represented the total U. S. resources for human air pollutant
exposure studies at that time. The locations of the five chambers are:
o Rancho Los Amigos, Downey, California
o University of Maryland, Baltimore, Maryland
o St. Vincent's Hospital, New York, New York
o Hospital for Sick Children, Washington, D. C.
o New York University, New York, New York
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A justification and specifications for the design and construction of
the CLEANS facility was presented to the EPA management in a detailed
report by Dr. Knelson titled "CLEANS, A Program for Clinical Environmental
Laboratory Research" dated December 13, 1971. The document also included a
combined report on the evaluation of the five human exposure facilities
visited by Dr. Knelson.
A design and construction contract for the CLEANS facility was signed
in April 1973. The facility was completed in May 1976. By December 1976 a
contractor was hired to operate and maintain the facility. The full complement
of pollutants that could be generated and controlled became available with
the completion of the Aerosol Pollutant System in March 1978. Work was
started on this phase of the project in August 1976.
The purpose of the CLEANS facility is to provide a unique national
resource for the study of the relationships between the environmental
pollutants and human health in a manner responsive to the continuing needs
of the Environmental Protection Agency.
For the following description, the CLEANS system is considered to
consist of five support systems. They are:
o Clinical Environmental Laboratories (CEL)
o Environmental System
o Gaseous Pollutant System
o Aerosol Pollutant System
o Physiological Data Acquisition System (PDAS)
CLINICAL ENVIRONMENTAL LABORATORIES
The Clinical Environmental Laboratories (CEL) consists of two identical
but environmentally independent 4 x 6 x 3.2 meters (13' x 20' x 10'6") high
exposure rooms.1,2 Each room was designed to comfortably house three test
subjects for extended periods of time. For exposure periods of less than
eight hours the beds may be removed, as indicated in Figure 1, to make room
for a larger number of subjects or special protocol task-related equipment.
Other basic equipment located in each chamber consists of the primary
physiological data acquisition devices, closed circuit TV, and protocol
task-oriented equipment as shown in Figure 2. Each CEL has a separate air
handling and environmental control system. The 0 to 150 foot-candle lighting
in each CEL is controlled in zones to permit separate medical test laboratory
and sleeping areas. CEL A, the one to the left of the entrance door, was
constructed in the mirror image of CEL B so that one air shower could serve
as the ingress and egress to both exposure rooms. The air shower in combina-
tion with a shoe sole scrubber prevents cross contamination of atmospheres
and reduces the entrance of outside dirt. Adjacent to the air shower,
emergency doors are provided for each CEL which open directly into the
laboratory control room. A one-way mirror in each door allows the console
operator to observe the test subjects. The emergency doors have panic bar
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Figure 2. Inside of exposure chamber B.
The physiological equipment is located on the right. The furthest rack
contains a multichannel display oscilloscope and an ultrasonic blood pressure
unit. The equipment rack to the right of the treadmill contains a Physiological
Data Acquisition System Control panel, intercom, and a Medical Gas Analyzer (MGA)
The next rack contains the spirometry equipment. The Body Plethysmograph is
located at the right.
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latch releases and open out from the front of each CEL to allow rapid exit.
Air-lock pass-throughs are situated next to the emergency doors for the
exchange of food and supplies into and out of the CEL without requiring the
entrance of service personnel.
To conserve space, the individual CEL bathrooms were located between
the exposure rooms and behind the air shower. Each bathroom is on the same
air supply as the connecting CEL but has a separate exhaust. Emergency
egress is provided between the back of each CEL through an extra door in
the CEL B bathroom opening into CEL A.
Type 304 alloy stainless steel sheet metal was used extensively in the
construction of the CEL interior and air handling system. Thus preventing
the possibility of outgassing of absorbed pollutants and the static attrac-
tion of aerosol particles. The 15 centimeter (6 inch) thick chamber walls
are fully insulated with staggered metal studs, foamed insulation, and
sheet steel outer panels to reduce the transfer of outside heat and noise.
The 3.2 meter high ceiling is constructed of insulated metal decking surfaced
on the underside with stainless steel to match the CEL walls. The CEL
floor which is on the same level as the control room is constructed of
removable panels that are perforated to allow passage of the exhaust air
from the CEL.
The air with pollutants enters the CEL through six 76 x 101.6 centimeter
(cm) (30 x 40 inch) adjustable vane registers in the ceiling and moves down
with a velocity variable between 7.6 and 15.3 meters/minute (25 and 50
ft./min). The air is then exhausted through the perforated floor. The
pollutants of interest are well mixed with the supply air before it enters
the CEL to provide a homogenous pollutant distribution throughout the CEL.
Therefore, the exposure dose is independent of the subject's position. The
return air plenums below each CEL approaches the volume of the CEL in size
to provide room for 5.9 square meters (63 square feet) of High Efficiency
Particle Air (HEPA) filters and 5.9 square meters of charcoal filters.
Presently, only the HEPA filters are in place. The purpose of the filter
banks are to remove dirt and unwanted contaminants from the recirculating
air stream.
CEL A differs from CEL B only in the addition of an extra 5.2 square
meters (56 square feet) of HEPA filters in the input air plenum and an
aerosol mixing chamber. During an exposure session that includes controlled
gaseous pollutant levels, the HEPA filters are bypassed by removing cover
plates from bypass openings over the filters in the return air plenum and
opening bypass louvers in the supply plenum over CEL A. To return to the
clean room starting conditions, the filter bypass louvers are closed. A
description of the total air handling system will be covered in the next
section.
An Environmental System, a Gaseous Pollutant System, an Aerosol Pollutant
System, and Physiological Data Acquisition Systems comprise the CEL support
systems located in four areas adjacent to the CEL exposure rooms (Figures 1
and 3). The Environmental System is located in a two-story with basement
machinery room to the right of CEL B. The Gas and Aerosol System share a
mezzanine above the control room and are supported by separate gas
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and aerosol generating rooms. A PDAS display and control console and four
PDP-11/40 computers with extensive peripherals are located in the control
room contiguous to the front of the CEL exposure rooms. The aerosol generator
is located in an adjacent room that has a separate heating and air conditioning
system to prevent the spread of aerosol particles, in the event of a leak,
to other parts of the building. The gaseous pollutants are maintained in a
separate gas bottle house outside the main building. The gases are brought
into the laboratory building through small bore tubing (6 mm).
Some of the safety measures incorporated in the operation of each CEL
are:
o Direct viewing of the exposure subjects through large glass
windows.
o Closed circuit TV view of exposure subjects.
o Continuous telemetry EKG monitoring of the exposure subjects.
o Continuous intercom communication between the subjects and the
M.D. conducting the tests.
o The electrical circuits in the CEL have 5 milliamps ground fault
current interrupter circuit breakers.
o All metal surfacing in the CEL are electrically bonded together
and connected to the power system ground and a buried counter-poise
ground.
o Fire warning alarms in each CEL are connected to smoke and heat
sensors throughout the building.
o All CEL support systems have limit alarms and automatic shut-down
sequences that warn the test conductor of abnormal conditions.
ENVIRONMENTAL SYSTEM
The function of the Environmental System is to produce and maintain
within prescribed limits the air flow, temperature, relative humidity, and
light level in the CEL as specified in the exposure test protocol. Except
for air flow, a feed back control system with electronic sensors and pneumatic
actuators accomplish this task. The following range of conditions can be
developed in each CEL:
Main Air Flow Rate 227-453 mVmin. (8,000-16,000 CFM)
Maximum Air Duct Velocity 305 meters/min. (1,000 feet/min.)
Make-up Air Flow 34 mVmin. (1,200 CFM)
Temperature Range 7-35°C (45-95°F.)
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Relative Humidity Range 30-70%
Light Intensity Range 0-150 foot-candles
CEL Pressure 2.54 mm (0.1 inches) of water (positive)
Sound Level NC-40
Clean Room Conditions 4000 particles/m3
where: m3/min. is cubic meters per minute
CFM is cubic feet per minute
mm is millimeters
A variable or steady state profile of set points from the Pollutant
Gas System PDP-11/40 computer provides the specified environmental con-
ditions that the Environmental System is to achieve within each CEL. The
profile for each parameter are entered into the computer by the System
Operator at the beginning of an exposure experiment, but they may be changed
during the course of the experiment. The computer also receives electrical
outputs from the Environmental System sensors in order that the conditions
within the CEL may be recorded on a digital history tape. As a backup,
fixed set points can be manually entered directly into the CEL environmental
Sipervisory Controls. If the computer fails, the controls are automatically
switched from computer to manual set point entry.
The path of the main recirculated CEL air flow, as shown in Figure 4,
starts at the output of the fan, passes through a sound trap, heating and
cooling coils, then into the CEL by way of the ceiling registers. The air
flow continues through the perforated CEL floor, through or around the
return air plenum filter banks, and finally on through a second noise trap
to the input of the fan. The air flow is varied by remote adjustment of
the pitch of the axial vane constant speed fan.
CEL A differs from CEL B by the additional static aerosol pollutant
mixing tank with an output sound trap and a HEPA prefilter bank with remote
controlled motorized filter bypass dampers. The additional items were only
installed in the air supply for CEL A because of the limited space in the
shorter distance between CEL B and the Mechanical Equipment Room. Identical
gaseous pollutant atmospheres may be produced in both CEL A and B, but only
CEL A has the additional equipment required for the introduction of homogenously
mixed aerosol pollutants.
Fresh air is brought Into the main air supply of each CEL by adding
make up air at a constant 34 mVmin. The outside air is prefiltered,
charcoal filtered, and heated or cooled to 5.3°C dry bulb (DB)/4.4°C wet
bulb (WB) (41.5°F/23.1°F) and then supplied to an air dryer. A rain curtain
of lithium chloride solution in the dryer, cooled to -1°C (30°F) dries the
air to -1°C DB/-4.9°C (23.1°F) WB. The air is then heated to the temperature
of the main CEL recirculated air stream. The desired humidity in the
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recirculated air supply is maintained by heating the make up air to 37.8°C
(100°F) and injecting dry-steam at a rate of 78.75 kilograms/hour (175
pounds/hour) on automatic demand for humidification.
The supervisory controllers and indicators for the temperature, humid-
ity, and lighting for each CEL are located in Environmental Control Console
equipment racks positioned adjacent to the dedicated PDAS computer. Graphic
Display Panels, as shown in Figure 5, are located at eye level above the
supervisory controls to provide a schematic diagram of the CEL air flow
systems with status indicators and alarms for the CEL air flow, damper
position, fan operation, and CEL air pressure.
To prevent outside contaminants from leaking into a CEL, the atmos-
phe-ic pressure within the CEL is maintained positive at 2.54 mm water
gauge. A pressure modulated damper in the environmental system exhaust
djcL, maintains the pressure with the make up air providing the pressurizing
f^rce. The uncontrolled bathroom exhaust vent accounts for about 40% of
the system venting.
As a safety precaution an emergency purge mode of operation ^as designed
i ito the CEL air flow system. When a purge mode is initiated, motorized
d?mpers are positioned so untreated outside air is pulled directly into the
C:L which then exhausts at the rate of 227 to 453 m3/min directly to the
ojt'.ide atmosphere. This provides a purge rate of 1 to 2 minutes for the
dilution of the CEL pollutant content down to 10 percent of the original
concentration.
A gas fired steam boiler with an output of 1,000,000 BTU per hour is
the central heating system for both CEL Environment Systems. The common
cooling unit uses a chilled glycol system with four compressors for a total
output capacity of 55 tons. The large heating and cooling capacity was
dictated by the requirement that the temperature and relative humidity for
either CEL may be changed from one extreme condition to the opposite extreme
condition with the system stabilizing to the new values within a three hour
period.
GASEOUS POLLUTANT SYSTEM
The Gaseous Pollutant System independently produces five common atmos-
pheric pollutants in the environmentally controlled air supply to each
CEL.3,4 The range of concentrations of the pollutant gases that can be
introduced either singly or in nonreactive combinations are as follows:
Gas Available Cone. Range Control Error
03 Ambient - 1.0 ppm ±5% or ±.005 ppm
CO Ambient - 150. ppm ±5% or ±1.0 ppm
NO Ambient - 2.5 ppm ±5% or ±.005 ppm
N02 Ambient - 1.5 ppm ±5% or ±.005 ppm
S02 Ambient - 1.0 ppm ±5% or +.01 ppm
10
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CONTROL CONSOLE
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Figure 5. Environmental control console graphic display panel
and supervisory controls.
11
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The Gaseous Pollutant System may be divided into the three main sections
of Gas Analysis, Gas Delivery and Gas Control. The three sections are
interconnected to implement a control loop with a digital computer as the
feedback element. The gas analysis section provides outputs to the computer
proportional to the concentration of each of the five pollutant gases. The
computer compares these outputs with the concentration-time profile previously
entered by the CEL system operator and varies the flow of each gas into the
laboratory to minimize the control errors. The actual control of the
pollutant concentrations involves numerous complex control functions that
have an effect on a large number of different items of equipment. Each
item of equipment provides an input or receives an output signal from the
computer through 32 digital-to-analog converter (D/A) and 88 analog-to-digital
converter (A/D) channels and 16 digital input and 12 buffered digital
output words. After the operator has performed the start up procedure, the
system operates automatically requiring only casual operator intervention.
Gas Analysis
The fourteen aerometric analyzers located in the mezzanine CEL support
area, as shown in Figure 6, are used to monitor the concentrations of the
five gaseous pollutants. Each analyzer may be configured to receive a gas
sample from one of the two CELs, a calibration manifold, or from a Safety
Sentry manifold. The Safety Sentry manifold is connected to air sample
ports in the CEL support areas. The configuration of any analyzer is
selected under supervision of the gas system computer or manually through
an indicating Configuration Panel located with the analyzers.
Multiple analyzers are required for each pollutant gas (five for
NO-NO and three for each of the other three gases) to provide a continuous
analysis of the pollutant in each CEL and monitor for possible pollutant
gas leaks in the support areas.
The analyzer for each pollutant operates on a principle that provides
specificity and sensitivity for the gas it is designed to measure.
The ozone analyzer provides a continuous readout of ozone concentra-
tions utilizing the principle of photometric detection of the chemilumines-
cence resulting from the reaction of ozone with ethylene. Ethylene is
provided from cylinders located in a Bottle House separated from the main
CLEANS facility.
The total sulfur analyzers provide a continuous measurement of the
concentration of gaseous sulfur containing compounds by photometric detec-
tion of the light emitted by the reaction of sulfur atoms with a hydrogen
flame and the pulsed fluorescents method where the S02 molecules are excited
by pulsing ultraviolet light and their characteristic decay radiation is
detected by a photomultiplier tube.
The nitrogen oxide or total nitrogen oxide and nitrogen dioxide (NO-NO )
analyzers can monitor the concentration of NO or NO . Nitrogen dioxide
(N02) concentrations are obtained by utilizing one analyzer to monitor NO
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Figure 6. Mezzanine support area.
The gas analyzers are on the right. The control panels for the Gaseous
Pollutant System are on the left. The Aerosol Pollutant System Control panels
and aerosol analyzers are located at the far end of the two rows of the
equipment racks.
13
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and a second to monitor NO. N02 is obtained by performing the subtraction
in the computer of N02 = NO - NO. The instrument utilizes the principal
of photometric detection of the chemiluminescence resulting from the reaction
of nitric oxide and ozone. N02 is measured by first converting it to NO
using a catalytic converter internal to the analyzer. Ozone (03) is produced
by the analyzer from oxygen (02) using a glow discharge technique. The
oxygen is provided in cylinders located in the Bottle House.
The carbon monoxide (CO) analyzer is a non-dispersive infrared analyzer
that provides a continuous readout of CO concentration.
A 7.6 centimeter (3 inch) diameter glass tube from each CEL is used to
transport 1000 liters of air per minute from each CEL to the mezzanine
lucrtion of the gas analyzers. A small volume of the sample flow if; drawn
through each of the 14 gas analyzers by a vacuum at the analyzer outlet.
The surplus sample air is exhausted outside the building. The excess
sample volume is used to reduce the transport time from the CEL to the
locetion of the analyzers. A central vacuum system maintains the proper
exhaust pressure at the outlet of each analyzer.
Zero and span checks or multipoint calibration of each analyzer are
performed under computer control of an integral calibration system. CO and
NO calibration is effected by the dilution of known concentrations of
reference gases (supplied by cylinders) with pure air generated on site.
Si.lfur dioxide (S02) calibration is effected by the dilution of S02 from a
penreation tube with pure air. Finally, the 03 analyzer calibration and
calibration of the converter efficiency for a NO-NO analyzer is accomplished
by a gas phase titration procedure involving the reaction of NO and 03 to
produce N02 and 02. The 03 is generated by the irradiation of pure air
with an ultraviolet lamp.
Gas Delivery
With the exception of ozone, all of the pollutant gases are delivered
to the air stream of each CEL from pressurized cylinders located in a
Bottle House outside the main CLEANS facility. Since 100% S02 and N02 are
liquids at room temperatures, the cylinders are located within a heated box
maintained at 29.4°C (85°F). Also, the S02 and N02 delivery lines are
heated from the Bottle House to the dilution point. The pollutant gases
are ultimately center injected into a high-efficiency bow-tie static mixer
where they are diluted with several hundred liters per minute of air from
the make-up air supply. This mixture is then injected into the CEL main
air stream in front of the axial vane fan.
03 is produced on site by the UV irradiation of 6 mVmin. (200 CFM) of
make-up air from the environmental chamber HVAC system. Ten 91.4 centimeter
(36 inch) long UV tubes (for each chamber) are utilized and the concentration
of ozone produced is controlled by varying the number of lamps that are
turned on.
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Gas Control
An automatic closed loop method is used to precisely control the
pollutant concentration in each CEL. The major components and their function
in the loop are as follows:
o The gas analyzer measures the pollutant concentration in the CEL
and produces a proportional analog output voltage (0-5 volt DC).
o An analog-to-digital (A/D) converter transforms the analog
voltage from the gas analyzer into digital words that are accept-
able to the PDP-11/40 computer.
o The computer compares the output of the A/D converter with a
previously stored concentration-time profile and executes a
control algorithm every 30 seconds to compensate for errors.
o A digital-to-analog (D/A) converter transforms the output of the
computer into a 0-5 volt D.C. analog voltage proportional control
signal.
o A mass flow controller permits a flow of concentrated pollutant
gas into the CEL air stream proportional to the control signal
from the D/A converter closing the loop around the CEL. A flow
meter in the flow controller provides a signal to the computer
proportional to the actual flow through the controller that may
be displayed.
The exception to the description of the control loop is for ozone
whose concentration is established by the number of energized ultra violet
lamps. Precise control is achieved by varying the duty cycle of one of the
lamps. Each lamp is controlled by a bit in a buffered word from the computer.
Up to ten control loops, one for each of the five gases in each CEL, may be
operated simultaneously and independently of each other.
The concentration-time profile for each pollutant gas may be specified
to have the shape of a sine wave, triangular wave, step function, exponential
function, or specified point-by-point for every 30 minutes. Constants for
the pollutant control algorithim were determined experimentally since they
depend upon the characteristics of the CEL and the pollutant gas being
controlled. The constants were chosen to provide the desired control
characteristics with minimum steady state error and no overshoot.
In the event of a computer or associated interface failure, the Gas
System switches from the automatic mode to the back up manual mode of
operation.
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Safety Features
Several safety features have been included in the Gas System that
protect both the exposure subjects and the operating personnel. Every
second the computer checks the status of all valve positions, flow meters,
power supplies, analyzers, and environmental parameters against preset
limits producing appropriate audible and visual alarms when the limits are
exceeded.
The output of each gas analyzer is wired directly to an audio-visual
alarm panel which will shut off the pollutant gas to the CEL when a preset
level is exceeded. This fail-safe system is independent from computer
operation or control.
All gases transported to the CEL from pressurized bottles must pass
ttircugh normally closed solenoid valves which close when power is inter-
rupted and flow restricting capillaries that prevent excessive gas flow in
the event the pressure reducing regulator fails.
The status of the gas system may be continuously observed on video
d\splay units in the mezzanine and the CEL control room and on demand by
the operator the data may be printed on a hard-copy unit. A magnetic
d gital history tape automatically provides a permanent record of the gas
system operation.
AEROSOL POLLUTANT SYSTEM
In addition to the gaseous pollutants, aerosols that are chemically
and physically compatible with the environmental conditions may be gener-
ated from water soluble materials and introduced into CEL A. Aerosol
physical characteristics are controlled within the following limits:5
o Size Range 0.1 to 1.0 urn MMD
o Mass Generated as Usable Aerosol 1 to 75 mg/min
o Mass Concentration in CEL 10 to 330 ug/m3 ± 10%
o Measurement Range of Monitors 0.01 to 10 urn diameter
Where: |jm is micrometer diameter
MMD is mass median diameter
mg/min. is milligram/minute
The Aerosol System consists of the three complex sections of Aerosol
Generation and Delivery, Aerosol Analysis, and Data Acquisition and Control.
The three sections contain the equipment, components, and a PDP-11/40
computer to form a control loop. The aerosol mass concentration in the CEL
16
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is computed from the output of aerosol analyzers, the relative humidity in
the CEL, and constants stored in the computer memory that describe the
chemical and physical characteristics of the generated aerosol. The computed
mass concentration and HMD are respectively compared to a concentration-time
profile and a size-time profile, previously entered in the computer. The
computer then varies the aerosol generator to minimize the control errors.
Once the start up procedures are performed and the System Configuration
File has been entered in the computer, the Aerosol System is capable of
operating during an entire experiment with minimal operator intervention.
The System Configuration File is the source of all experimental constants
and variables.
Aerosol Generation and Delivery
Aerosols are generated by nebulizing an aqueous solution containing
the aerosol material. Multiple spherical nebulizers are used, each pro-
viding droplets at a constant rate. Compressed air provides the mechanical
forces required to atomize the liquids. The droplets that are produced are
equilibrated with air at the same relative humidity as maintained in CEL A.
The final equilibrated size of the resulting particles is controlled by
varying the concentration of the material in the generating solution. The
mass generation rate is controlled in part by varying the number of nebu-
lizers used. The concentration of the solution to be nebulized is controlled
by varying the flow rates of purified water and of the concentrated solution
through a static mixer. A schematic flow diagram of the aerosol generator
is provided in Figure 7. From the static mixer the solution enters a
constant pressure tank which is pressurized with regulated air. Excess
liquid is drained from this tank through a solenoid valve operated by a
float switch. The solution passes from the constant pressure tank through
solenoid valves and flow indicators to the nebulizers. The nebulizers are
arranged in banks of 16 each. The solution delivery to the nebulizers is
controlled in the binary format of 1, 2, 4, 8, 16, 32, and 64 nebulizers by
the solenoid valves which are activated by the computer. By this arrange-
ment any number of nebulizers from 1 to 127 can be activated.
Each nebulizer consists of a hollow glass sphere about 2 centimeters
in diameter attached to a plastic base. Compressed air is forced into the
sphere through a base mounting and is ejected through a small orifice in
the side of the sphere. The solution to be atomized flows over the glass
surface as a uniform liquid film. The film is ruptured by the air flowing
from the orifice forming small droplets. A small sphere mounted directly
in front of the orifice removes the largest droplets by impaction. The
nebulizer produces droplets over a range of sizes with mass median diameter
of approximately 3.5 urn. The liquid flow rate over each active nebulizer
is 25 cubic centimeters/ minute.
The droplet laden air flowing from the nebulizer banks is equilibrated
in a two foot square drying chamber with a portion of air taken from the
recirculated air supply for CEL A. The drying air mixes with the droplets
reducing them to their equilibrated diameter. Thus, the final size of the
aerosols is controlled by the amount of water in solution with the soluble
compound and the relative humidity in the CEL.
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From the drying chamber the aerosol flows to a motorized damper system
which permits bypassing a portion of the flow through a HEPA filter used as
a fine control of particle concentration in the CEL. The major methods of
controlling the particle concentration is the number of nebulizers receiving
aerosol solution flow. A second up-stream motorized damper system permits
the choice of allowing the aerosol to flow into the CEL aerosol mixing
chamber and on into the CEL or, into a start-up duct where the aerosols are
filtered out before the air stream reenters the CEL. The start-up duct
allows the aerosol monitors to measure the output of the generator and the
system to stabilize at the desired concentration and size before actual
delivery of the aerosol to the CEL. Up to 28 m/min. (1000 CFM) of air is
diverted from the CEL recirculated air stream through the aerosol delivery
system and is returned to the CEL system with or without aerosol particles.
Stainless steel was used in the construction of the dampers and ducts to
prevent corrosion and static charge build up that would attract particles
to the surface areas.
Aerosol Analysis
Because the wide range of particle sizes that can be delivered to the
CEL is beyond the range of one measurement methodology, two types of aerosol
monitors are used to characterize the size distribution in the CEL. An
Electrical Aerosol Analyzer (EAA)6 with a measurement size range of 0.0032
to 1.0 micron and an Optical Particle Counter (OPC)7 with a measurement
size range 0.3 to 10.0 microns provide the required range span. The inter-
polation between the EAA and OPC size ranges is based on a linear interpolation
of the distribution of particle mass with respect to the logarithm of the
diameter which is performed by the Aerosol Computer as it receives the
output of the analyzers. Due to inherent inaccuracies in the measurements
of particles smaller than 0.01 microns they are ignored.
Two complete sets of EAA and OPC instruments are utilized by the
Aerosol System to provide redundancy in case of an instrument failure. The
output signals of both the EAA and OPC are used by the aerosol computer to
determine the error signals to maintain the desired aerosol mass concentra-
tion within the CEL. A Beta Mass Monitor (BMM) instrument is also used as
an independent, noncontrolling measurement of the CEL aerosol concentration.
The Electrical Aerosol Analyzer (EAA) operates on the principle that
the electric mobility of a charged particle is inversely related to the
size of the particle. An aerosol air sample from the CEL is drawn into the
analyzer by a vacuum pump on the exhaust port of the analyzer. Once in the
analyzer the particles are charged and then carried by a constant air
stream through a cylindrical condenser. The electric field of the condenser
is varied in discreet steps where each charging voltage is selected to
precipitate particles smaller than the selected size. The size depends
upon the charged particle mobility in the electric field. The charges on
the lower mobility unprecipitated particles are detected by an electrometer
connected to a digital voltmeter and the aerosol computer. Particle size
distributions are determined by the differences in the concentrations of
19
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unprecipitated particles measured at each successive voltage step of the
electric field. The algorithms and constants used to compute the particle
number, surface and volume distributions are stored in the computer. They
may also be determined from the electrometer current measurements displayed
on the digital voltmeter using a programable calculator.
The Optical Particle Counter (OPC) measures the intensity of the light
scattered by individual particles as they pass through a high intensity
light beam. A photomultiplier tube detects the light scattered from the
particles and produces an electric pulse whose amplitude and frequency
corresponds to the size and number concentration respectively of the par-
ticles in the aerosol sample. The aerosol size distributions are deter-
mined by sorting the pulses that are produced according to their amplitude.
A vacuum pump within the analyzer draws the aerosol sample from the CEL
into the detecting chamber.
The Beta Mass Monitor (BMM) measures the density of the aerosol material
disposition on a filter strip. The difference in the beta radiation penetra-
ting a clean filter area and an area where aerosol particles were collected
is used to compute the mass of the aerosol sample. The amount of beta
radiation attenuation is a function of the mass of collected material over
a fixed period of time. A microprocessor in the analyzer also determines a
zero reference offset constant from a clean filter to compensate for the
de;is;ty of the filter material.
To minimize the effects of temperature and humidity changes on the
aerosol samples, the EAA and OPC instruments are housed in closed temperature
controlled cabinets with insulated stainless steel sample lines to the CEL.
Electrical signals from a temperature sensor in the CEL are compared to the
cabinet temperature which is maintained at the same level as the CEL. A
refrigeration unit in each cabinet is used to reduce the temperature rise,
due to the heat output of the instruments, to the required level.
Individual sample lines from CEL A were provided for each analyzer
since large flow volumes are required, 7 to 54 liters/minute per instrument,
and the precision of the concentration measurement is affected by the
accuracy and stability of the sample flow. During the aerosol start-up
period, the sample ports of the analyzers are switched by large bore solenoid
valves to sample lines from the start-up duct. Passive diluters are automat-
ically switched into each sample line when needed to prevent measurement
errors due to sample saturation of the analyzers.
An automatic calibration check is provided for the OPC at predetermined
intervals specified by the operator. During the calibration cycle, the
sample input port of the OPC is diverted to the output of a monodispersed
polystyrene latex aerosol generator. If the response of the OPC to the
calibration aerosol is outside the specified tolerance of a computer stored
calibration value, the OPC is automatically removed from on-line status by
the computer and replaced with the backup OPC.
20
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Due to the measurement ranges and analysis techniques, direct calibra-
tions of the EAA and BMM instruments are performed at the manufacturers
with sophisticated and expensive aerosol generation and measurement equipment.
Therefore, indirect calibration tests are conducted by comparing the results
of measurements made by the instruments on aerosols delivered to the CEL
with the chemical and physical analysis of the aerosol material collected
simultaneously on filters and cascade impactors within the CEL.
The calibration data is entered into the aerosol computer at the
beginning of an experiment when the System Configuration File (SCF) is
established. The SCF contains the exposure profiles, equipment configu-
rations, alarm limits, calibration data, and any other constants and variables
necessary for precise automatic control of the aerosol system.
Data Acquisition and Control
Precise control of the aerosol mass median diameter and mass con-
centration in CEL A is accomplished by computerized data acquisition of the
system parameters and closed loop control of the aerosol generator. Infor-
mation as to the aerosol size distribution in CEL A or the start-up duct is
obtained from the on-line EAA and OPC and used by the computer to determine
the total mass concentration of particles. The relative humidity in the
CEL is also used in the determination of mass concentration since the
generated hygroscopic materials accumulate varying amounts of water depending
upon the moisture content of the air.
The computed aerosol size distribution and mass concentration are
compared to a concentration-time profile stored in the computer. Every ten
minutes new generator and delivery damper control commands are computed
from a control algorithm. This provides sufficient delay for the system to
stabilize after a perturbation and permits a reliable measurement and
computation to be made of the new CEL concentrations.
The time-concentration profiles used for the Aerosol System are similar
to those used for the Gaseous Pollutant System. Selection and entry of the
exposure profiles into the computer are performed when the SCF is constructed
and specified. During the course of the experiment the operator can change
the profile in the SCF to meet new requirements of a protocol.
A limited manual control procedure can be used to replace the computerized
automatic control of the aerosol system in the event of a computer failure.
The manual controls are normally inoperative in the automatic mode to
prevent inadvertent override errors. But, the control mode may be switched
from automatic to manual when necessary.
Safety Features
Several safety features have been designed in the system such as
continuous computer status checks of the conductivity of the aerosol gen-
erator solution, operational checks of the aerosol monitors, position of
21
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dampers, air flows, and a sentry timer to detect computer failure. There
are several levels of audible and indicating alarms that must be acknowledged
with the proper response within a short time or the system will default to
a fail safe shut down. System limits specifications entered into the SCF
are the triggering points for the alarms. They may be set to up-dated
values as specified by the protocol.
A video display console with a hard-copy option is used by the system
operator to interact with the computer. A permanent record of the monitoring
data, status information and text entries are computer recorded on a magnetic
digital history tape.
PHYSIOLOGICAL DATA ACQUISITION SYSTEM (PDAS)
An automated system of medical instruments under operator-computer
control is utilized to provide an efficient means to perform noninvasive
cardiopulmonary function evaluations of human subjects during the performance
of an exposure protocol. Each Clinical Environmental Laboratory is assigned
an independent Physiological Data Acquisition System consisting of instrumen-
tation for standard clinical measurements (Figure 2), signal conditioning
equipment, a PDP-11/40 computer, an operator control console (Figure 8),
and acquired data displays and recording devices.
PDAS Measurements
The medical hardware interfaced with each PDAS has been designed to
measure the following on a test subject:
o Thoracic gas volume, functional residual capacity, airway resist-
ance, and static and dynamic compliance. A closed 600 liter
chamber or body plethysmograph (body box) instrumented with a
mouth shutter, a pneumotach, three pressure transducers, a con-
trolled leak vent and a calibration pump is used to perform the
measurements. The pressure transducers measure the pressure
differentials found between the mouthpiece and inside the box for
mouth pressure, inside and outside of the box for box pressure,
and the pressure differential across a fixed resistance or pneumo-
tachometer for flow. The calibration pump varies the box pressure
a known amount to test the system as it relates to various sizes
of test subjects and their displacement of the empty box air
volume.
o Forced vital capacity, vital capacity, forced inspiratory capacity,
and maximum voluntary ventilation. A 12 liter dry rolling seal
spirometer is used for these measurements of the subject's lung
volume and air moving capacity. The large low-friction piston of
the spirometer moves as the subject forces air into or removes
air from it during the tests. From the spirometer piston position
and temperature signals, the PDAS computer determines the flow
volume, the flow rate and the total volume as a result of the
subject breathing into the spirometer.
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Figure 8. Physiological data acquisition system operator control consoles.
The PDAS control consoles are positioned in front of the emergency entrance
doors of the two exposure chambers. The CEL A console is located on the left
and the CEL B console is located on the right. Each console contains a Functional
Keyboard, an intercom, two video displays, two time of day digital clocks, closed
circuit TV controls, a display scan converter and a video hardcopy unit.
The center door between the CEL's is the entrance to the Air Shower which is
the normal entrance to each CEL.
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o Pulmonary gas distribution and exchange test of oxygen single
breath, nitrogen washout, carbon monoxide diffusion, and helium
equilibration. A Medical Gas Analyzer (MGA) automatic mass
spectrometer is used for these tests. The MGA can measure the
content of oxygen (02), helium (He), carbon dioxide (C02), nitro-
gen (N2) and an isotope of carbon monoxide (C180) in a gas mixture.
o The subject's systolic and diastolic blood pressures measured
with an ultrasonic blood pressure unit under computer control.
o Cardiovascular and pulmonary measurements, including minute
ventilation, electrocardiography, respiratory flow and volume,
oxygen consumption and carbon dioxide production may be made
while the subject is exercising on a treadmill. These measure-
ments may also be made pre-exercise and during post-exercise
subject recovery.
Measurement information from the medical device hardware is acquired
by the computer and associated peripherals for processing and analysis and
then stored on a digital system history tape. Functional keyboards and
visual displays both in the exposure chamber and in the control room consoles
are used by the principal operator as the interactive point for test control
and data assessment. The displays present information in both alphanumeric
and graphical forms. Permanent records of the displayed data may also be
orDduced on paper by a hard-copy unit.
Operator-Computer Interaction
The subtle effects of professional judgements and interpretations on
the measured data are reduced to a minimum in the PDAS by computer control
of the clinical instrumentation. A minimal amount of operator intervention
between the test subject and the PDAS is provided through the Functional
Keyboards shown in Figure 9. By depressing keys under the cueing of the
computer, the operator may select a series of specially programmed clinical
tests. A flickering light in the push button indicates to the operator the
available alternative selections. Sequential operator instructions appear
on the video display associated with the keyboard after a selection has
been made. The operator then guides the test subject through the performance
of the tests based on the displayed instructions. A graphical display of
the acquired data is evaluated by the operator in reaching a decision to
keep the data or repeat the test. Joysticks, Mark, and Fine Adjust buttons
are provided to allow the operator limited interaction with the computerized
pattern recognition of the physiological data signals. In designing a
protocol, an investigator is required to select the tests that have been
preprogrammed in the computer unless he wishes to make software changes.
He can, however, arrange the sequence of tests in any order that meets the
requirements of the protocol. This flexibility was designed into the
Functional Keyboard. A possible sequence of events in following a protocol
using the Functional Keyboard might be:
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Figure 8. Physiological data acquisition system operator control consoles.
The PDAS control consoles are positioned in front of the emergency entrance
doors of the two exposure chambers. The CEL A console is located on the left
and the CEL B console is located on the right. Each console contains a Functional
Keyboard, an intercom, two video displays, two time of day digital clocks, closed
circuit TV controls, a display scan converter and a video hardcopy unit.
The center door between the CEL's is the entrance to the Air Shower which is
the normal entrance to each CEL.
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o Pulmonary gas distribution and exchange test of oxygen single
breath, nitrogen washout, carbon monoxide diffusion, and helium
equilibration. A Medical Gas Analyzer (MGA) automatic mass
spectrometer is used for these tests. The MGA can measure the
content of oxygen (02), helium (He), carbon dioxide (C02), nitro-
gen (N2) and an isotope of carbon monoxide (C180) in a gas mixture.
o The subject's systolic and diastolic blood pressures measured
with an ultrasonic blood pressure unit under computer control.
o Cardiovascular and pulmonary measurements, including minute
ventilation, electrocardiography, respiratory flow and volume,
oxygen consumption and carbon dioxide production may be made
while the subject is exercising on a treadmill. These measure-
ments may also be made pre-exercise and during post-exercise
subject recovery.
Measurement information from the medical device hardware is acquired
by the computer and associated peripherals for processing and analysis and
then stored on a digital system history tape. Functional keyboards and
visual displays both in the exposure chamber and in the control room consoles
are used by the principal operator as the interactive point for test control
and data assessment. The displays present information in both alphanumeric
and graphical forms. Permanent records of the displayed data may also be
Deduced on paper by a hard-copy unit.
Operator-Computer Interaction
The subtle effects of professional judgements and interpretations on
the measured data are reduced to a minimum in the PDAS by computer control
of the clinical instrumentation. A minimal amount of operator intervention
between the test subject and the PDAS is provided through the Functional
Keyboards shown in Figure 9. By depressing keys under the cueing of the
computer, the operator may select a series of specially programmed clinical
tests. A flickering light in the push button indicates to the operator the
available alternative selections. Sequential operator instructions appear
on the video display associated with the keyboard after a selection has
been made. The operator then guides the test subject through the performance
of the tests based on the displayed instructions. A graphical display of
the acquired data is evaluated by the operator in reaching a decision to
keep the data or repeat the test. Joysticks, Mark, and Fine Adjust buttons
are provided to allow the operator limited interaction with the computerized
pattern recognition of the physiological data signals. In designing a
protocol, an investigator is required to select the tests that have been
preprogrammed in the computer unless he wishes to make software changes.
He can, however, arrange the sequence of tests in any order that meets the
requirements of the protocol. This flexibility was designed into the
Functional Keyboard. A possible sequence of events in following a protocol
using the Functional Keyboard might be:
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CSC
COMPUTER SCIENCES CORPORATION
o
ZOOM
DISPLAY POSITION
-CURSOR POSITION
Figure 9. Typical functional keyboard layout.
25
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(Reference Figure 9)
o Press FILE OPEN.
o Press RESET and type in the operator and experiment names on the
console keyboard terminal (DEC writer).
o Press GO and type in the test subject's name. The subject's
demographic data is entered using the numeric keys on the Func-
tional Keyboard.
o Press MARK to save the above entries in the computer disk memory.
o Press GO to proceed. The keys for the menu of tests will flicker.
o Press one of the top row of keys to initiate the desired test,
i.e., Plethysmography, Spirometry, Gas Exchange, Stress Testing.
A steady light will appear in the depressed key and the other top
row key will be extinguished. The keys under the one selected
will flicker indicating their availability.
o The test is then performed in the desired sequence. The RESET
key may be used to override a selection.
o The GOOD DATA or POOR DATA keys are depressed to enter the collected
data into the computer RESULT file.
o When the test sequence is complete the FILE CLOSED key is used to
mark the end of the RESULT file.
Standard TV monitors are used for both the video displays and closed
circuit TV viewing of the subject in the CEL. Two TV monitors mounted in
the low control console next to the Functional Keyboard allow simultaneous
observation of the subject and his displayed test results. A scan converter
is used to obtain a standard TV signal from the computer display signal. A
paper hard-copy record may be produced of the pictures and data appearing
on the TV monitors by pressing the HARD COPY key on the Functional Keyboard.
As stated before, all acceptable data is recorded on a digital tape for
later retrieval and further processing at a later time.
As a backup for the PDAS or for validation of the PDAS acquired data,
all of the medical devices may be used off-line or independent of the
computer. A switch is provided on each clinical instrument for easy trans-
fer from on-line to off-line mode of operation where the manual controls on
the instrument are not inhibited. Additional computer backup is provided
through the use of a UNIBUS switching system that allows the PDAS computers
and peripherals to be interchanged from one CEL to the other. For example,
if the computer system for CEL A fails and the computer for CEL B is not in
use, it can be used for the CEL A PDAS computer. This provides continuity
without expensive redundancy.
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PDAS Calibration
Four related calibration procedures are used for PDAS to insure that
the acquired data is precise and represents the real effect of subject
exposure rather than system artifacts. The sequence of calibration pro-
cedures are:
o Engineering adjustments, where NBS traceable instrumentation or
standards accepted in clinical medicine are used in the alignment
and adjustment of the interface and signal conditioning equipment
between the electrode/transducer devices and the computer input.
All analog channel hardware such as the Analog Input Buffers
(AIB) for each medical device are included in the procedure.
o Comprehensive calibration, where a NBS traceable signal source is
used in place of the electrode/transducer to test the input-to-
output precision of the acquired data. The Analog-to-Digital
Converters and computer functions are included in this procedure
of comparing the acquisition and processing of known inputs with
numerical values entered via the PDAS keyboard directly into the
computer.
o Dynamic calibrations are performed next to characterize the
dynamic response of each channel of the PDAS.
o Time-of-Use checks utilizes built-in standard signals to provide
an automatic calibration check before and after the performance
of the subject's tests. Program software is used when necessary
to prompt the operator and generate a display of the calibration
results.
In addition to the calibration procedures, each software algorithm has
been validated by comparing data obtained by a physician using the clinical
equipment in the off-line operating mode with the on-line PDAS acquired
data.
PDAS Safety
The protection of the rights, health, welfare, and safety of the test
subjects has prime importance in the operation and maintenance of the PDAS
systems. To insure this, the following steps are mandatory prior to and
during the noninvasive physiological tests:
o All electrical equipment that is directly connected or may come
in contact with the test subjects, must pass an electrical safety
examination that has been approved for hospital equipment.
o The ECG of each test subject is continuously monitored and can
trip preset rate alarms. A wireless telemetry system is used to
allow free movement of the subjects.
27
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o The test subjects are under the constant observation of a Medical
Doctor or a medical technician with an MD on immediate call in
the building housing the CLEANS facility. A closed circuit TV,
large windows in each CEL, and a voice intercom system are used
to observe and communicate with the subjects.
o All test subjects are informed of all procedures and trained to
perform the required test maneuvers. Their performance is moni-
tored with safety limits that must not be exceeded such as a
maximum heart rate for the physical condition and age of the
subject.
o All test protocols are reviewed by the "Committee on the Pro-
tection of the Rights of Human Subjects" at the University of
North Carolina School of Medicine to insure that the risks are
comensurate with the information to be gained.
o Each candidate subject is given a physical examination before
acceptance as a participant in an experimental protocol.
A documented Quality Assurance Program for CLEANS, in addition to the
above operating prerequisites, insures safe operating conditions and that
the nreasured data contains the quality characteristics of accuracy, pre-
cision, representativeness, and completeness.
COMPUTERS AND PERIPHERALS
A total of four PDP-11/40(35) computers are used in the CLEANS system.
One for the Gaseous Pollutant and Environmental System, one for the Aerosol
Pollutant System and one for each CEL PDAS. In addition to the basic task
of system control and data acquisition, each computer must support display
and plotting peripherals that require a major part of the program running
time. Therefore, a single computer would have been inadequate to handle
the necessary tasks. To prevent catastrophic system outages due to chain
reaction failures, each computer and its peripherals function independently
of the others.
The configuration of the computer processors and peripherals was
designed for maximum efficiency in performing the data gathering tasks with
a minimum of operating personnel. Once the system software has been written,
the system operators do not require a knowledge of programming. The computer
configuration for each of the CLEANS support systems are:
Environmental and Gaseous Pollutant System:
o PDP-11/35 central processor with 64K core memory, EIS (extended
instructor set), FIS (floating point instruction set), RT-11
operating system, and memory management.
o A printer data terminal and two video display terminals.
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o A 1,200,000 word moving head storage disk. For program and
temporary data storage.
o Two nine track tape drives. Permanent data storage, history
tapes.
o Line frequency clock for time base.
o Digital inputs and buffered outputs (sixteen 16-bit words input
and twelve 16-bit words output).
o Analog-to-digital converter (88 channels).
o Digital-to-analog converter (32 channels).
Aerosol Pollutant System:
o PDP-11/35 central processor with 64K core memory, EIS, FIS, and
RSX-11M operating system.
o A printer data terminal and two video graphic display terminals
with a hard-copy printer.
o Two 2,400,000 word moving head storage disks.
o A nine track tape drive.
o Line frequency clock.
o Analog-to-digital inputs.
o Digital-to-analog outputs.
o Digital inputs and buffered outputs.
o A high speed data printer.
Physiological Data Acquisition System (two each):
o PDP-11/40 central processor with 28K core memory, EIS, FIS, and
RSX-11A operating system.
o A printer data terminal.
o A 1,200,000 word moving head storage disk.
o Two nine track tape drives.
o Line frequency clock time base.
o Video display outputs.
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o Analog-to-digital converters for PDAS Analog Input Buffers (AIB).
There are 45 AIB channels.
o Digital-to-analog converters for PDAS AIB.
o Digital inputs and outputs for PDAS Functional Keyboards.
Fortran is used in the programming of all computer systems.
The selection of the software operating system and configuration of
the peripherals for each system was based on the need and availability at
the time of the system design. A continued program of technological improve-
ment interdigitized with the exposure research studies will, as a future
goal, reduce the number of different operating systems to improve data flow
and programming efficiency.
INFORMATION SOURCES ACKNOWLEDGMENT
Some of the information in the preceding description was obtained from
Work Plans, Final Engineering Reports and Operation and Maintenance Manuals
produced by the following contractors:
o Computer Science Corporation who was the prime contractor for the
design and construction of the CLEANS facility.
o Rockwell International Corporation who designed and constructed
the Pollutant Gas System and is currently the O&M Contractor for
the CLEANS facility.
o Environmental Research and Technology Corporation who designed
and constructed the Aerosol Pollutant System.
All documents and reports are the property of the Environmental Protection
Agency and are on file at the Health Effects Research Laboratory in Chapel
Hill, North Carolina.
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REFERENCES
1. Computer Science Corp. CLEANS/CLEVER Project Final Engineering Report
(Overview & Physical Facilities). Contract No. 68-02-0768, Falls
Church, VA, 1977. 107 pp.
2. Computer Science Corp. CLEANS/CLEVER Project Work Plan, Revision 4,
Contract No. 68-02-0768, Falls Church, VA, 1975. 329 pp.
3. Rockwell International Air Monitoring Center. EPA/CEL Clinical Environ-
mental Laboratory. Final Engineering Report No. SC580.61FR, Newbury
Park, California, 1976. 329 pp.
4. Rockwell International Air Monitoring Center. EPA/CEL Clinical Environ-
mental Laboratory Pollutant Gas Control and Monitoring System Operation
and Maintenance Manual. Volume 1, No. SC580.640M, Newbury Park,
California, 1978. 445 pp.
5. Environmental Research and Technology, Inc. Aerosol Generation,
Monitoring and Control System for the Controlled Environment Labora-
tory Final Report, Contract No. 68-02-2300. Westlake Village, California,
1978. 162 pp.
6. Liu, B. Y. H, Whitby, K. T., Pui, D. Y. H. A Portable Electrical
Analyzer for Size Distribution Measurement of Submicron Aerosols.
Journal of the Air Pollution Control Association 24(11):1067-1072,
1974.
7. Climet Instruments Company. A Description of the CI-208, Technical
Note #27. Redlands, California. 18 pp.
31
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TECHNICAL REPORT DATA
(Please read 1'iitrtictions on the reverse before completing)
1 REPORT NO.
EPA-600/1-78-064
4. TITLE AND SUBTITLE
DESCRIPTION OF THE CLEANS HUMAN EXPOSURE SYSTEM
5. REPORT DATE
November 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHORfSI
Arthur A. Strong
s. PERFORMING ORGANIZATION REPORT NO.
3. RECIPIENT'S ACCESSION" NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Clinical Studies Division
Health Effects Research Laboratory
U.S. Environmental Protection Agency
10. PROGRAM ELEMENT NO.
1AA601
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
Heal til Effects Research Laboratory
Office cf Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
RTP,NC
14. SPONSORING AGENCY CODE
EPA 600/11
15. SUPPLEMt NTARY NOTES
16-ABSTRAC" Legislative mandates require the Environmental Protection Agency to
determine the levels of risk to the human population exposed to air pollu-
tants and establish standards to limit that risk. Two stainless stfcel
Controlled Environmental Laboratories (CEL) were constructed in the EPA
Clirical Studies Laboratory Facilities in Chapel Hill, North Carolina to
determine the pulmonary and cardiovascular health problems of humans ex-
posed to ambient levels of selected air pollutants. Both gaseous and water
soluble particulate pollutants can be generated in desired concentrations
in accurately controlled air flows, temperatures, humidities, and light
levels. Each CEL operates independently of the other, and the pollutants
can be introduced either singly or in combinations. Four PDP-11/40 computers
are required to automate all control, measurement, and data acquisition for
the CEL environment and the physiological measurements of the test subjects.
The exposure system was designed to house six test subjects for several
weeks without interruption of the exposure insult.
A brief description of the exposure laboratories and the support
systems including their functions is provided. The methodology used to
measure and control the conditions in each CEL is included along with a
list of the physiological capabilities.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
test chambers
humans
environmental
laboratories
air pollution
CLEANS
tests
06 F, L
14 B
13 DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19 SECURITY CLASS (This Reporr/
UNCLASSIFIED
21. NO. OF PAGES
20 SECURITY CLASS (This page)
UNCLASSIFIED
_3L
22. PRICE
EPA Form 2220-1 (9-73)
32
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