EPA-600/R-95-088
July 1995
FINAL REPORT
MICROBIOLOGICAL SCREENING OF THE INDOOR AIR QUALITY
IN THE
POLK COUNTY ADMINISTRATION BUILDING
D. W. VanOsdell, K. E. Leese, and K. K. Foarde
Center for Environmental Technology
Research Triangle Institute
P. O. Box 12194
Research Triangle Park, NC 27709-2194
EPA Cooperative Agreement No. CR-817083-01-1, Task 11
EPA Project Officer: Russell N. Kulp
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
Research Triangle Park, NC 27711
Prepared for:
U. S. Environmental Protection Agency
Office of Research and Development
Washington, D.C. 20460
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TECHNICAL REPORT DATA
{Please read Instructions on the reverse before compk ||| |([| [j |||||| I I III 1 '! II III i
1. REPORT NO. 2.
EPA-600/R-95-088
3 111 llll i: mill III III III! Mllll i
V PB95-243085 j
4. TITLE AND SUBTITLE
Microbiological Screening of the Indoor Air Quality in
the Polk County Adminstration Building
5. REPORT DATE
July 1995
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
D. W. VanOsdell, K.E. Leese, andK.K. Foarde
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME ANO ADDRESS
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, North Carolina 27709-2194
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CR817083-01-1, Task 11
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 2/94 - 2/95
14. SPONSORING AGENCY CODE
EPA/600/13
is.supplementary notes^ppqq project officer is Russell N. Kulp, Mail Drop 54, 919/541-
7980. :A/
16' ABSTRACTThe report gives results of a microbiological screening of the indoor air
quality in the Polk County (Bartow, Florida) Administration Building (PCAB), a
large negatively pressurized building, not known to be biocontaminated. The micro-
biological screening included bioaerosol, bulk material, condensate, surface, and
building floor dust samples taken at multiple locations. In general, the microbial
results were consistent with the PCAB's being a non-problem building. However,
the study was too limited in both duration and number of sample locations to com-
pletely evaluate the building. The results of a few samples indicated microbiological
conditions that might warrant further investigation, but were not of themselves ade-
quate to indicate a building-wide problem.^,.
" . \
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. cosati Field/Croup
Pollution
Buildings
Bioassay , .
Microbiology
Condensates
Dust
Pollution Control
Stationary Sources
Indoor Air Quality
Microbiological Screen-
ing
Bioaerosols
13 B
13 M
06A.06C
06M
07D
11G
13. DISTRIBUTION STATEMENT .
Release to Public
19. SECURITY CLASS (This Report/
Unclassified
21. NO. OF PAGES
36
20. SECURITY CLASS (This pagej
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
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FOREWORD
The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation's
land, air, and water resources. Under a mandate of national environmental laws, the Agency
strives to formulate and implement actions leading to a compatible balance between human
activities and the ability of natural systems to support and nurture life. To meet these mandates,"
EPA's research program is providing data and technical support for solving environmental
problems today and building a science knowledge base necessary to manage our ecological
resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for investigation of
technological and management approaches for reducing risks from threats to human health and the
environment. The focus of the Laboratory's research program is on methods for the prevention and
control of pollution to air, land, water, and subsurface resources; protection of water quality in
public water systems; remediation of contaminated sites and groundwater; and prevention and
control of indoor air pollution. The goal of this research effort is to catalyze development and
implementation of innovative, cost-effective environmental technologies; develop scientific and
engineering information needed by EPA to support regulatory and policy decisions; and provide
technical support and information transfer to ensure effective implementation of environmental
regulations and strategies.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It
is published and made available by EPA's Office of Research and Development to assist the user
community and to link researchers with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
i i i
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ABSTRACT
Designing and operating a ventilation system for increased outdoor air rates, as
required by ASHRAE Standard 62-1989, improves indoor air quality (IAQ) but is
thought to extract a high penalty in energy costs and potentially increased microbial
contamination in a hot, humid climate. The relationships between !AQ and comfort,
building energy usage/cost, and building microbial contamination have not been
studied systematically. A two-part research program into the impact of increased
outdoor air rates (per ASHRAE 62-1989) on building microbial contamination and the
cost of providing that outdoor air was initiated by RTI for the U. S. EPA. The Polk
County Administration Building (PCAB), a negatively pressurized large building, not
known to be biocontaminated and already part of a radon abatement project, was
selected for the ventilation study. The building environmental parameters, ventilation
system, and air exchange characterization planned for the radon project provided
important data to the microbiological and energy study. As planned, microbial
contamination and energy costs were to be assessed with the building in its native
state and after pressurizing and otherwise modifying it to ASHRAE 62-1989. In the
course of the radon study, however, the PCAB ventilation system was not modified as
expected, and further study of biocontamination and energy costs was deemed
unwarranted. The microbiological screening of the PCAB in its native state is the
subject of this report, and the energy / cost analysis is the subject of another report.
The microbiological screening included bioaerosol, bulk material, condensate,
surface, and building floor dust samples, most taken at 6 indoor locations on 3 floors.
A screening study is too limited in both duration and number of sample locations to
completely evaluate a building. However, in general, the microbial results were
consistent with the PCAB being a non-problem building. The results of a few samples
indicated microbiological conditions that might warrant further investigation, but were
not of themselves adequate to indicate a building-wide problem.
V_j; \ ' J
i v |
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TABLE OF CONTENTS
Section Page
Abstract i
Figures v
Tables vi
1.0 Background 1
2.0 Building HVAC System 4
2.1 Overview of Building Design 4
2.2 HVAC System Description .4
3.0 Experimental 7
3.1 Introduction 7
3.2 Procedures 7
3.2.1 Overview 7
3.2.2 Test Locations 8
3.2.3 HVAC System Sampling 10
3.2.4 Indoor Environment Evaluation 11
3.2.5 Biocontaminant Sampling 11
3.3 Data Quality Indicators 15
3.4 Quality Assurance 16
3.4.1 Cleanliness 16
3.4.2 Material Moisture 17
3.4.3 Surface and Bulk Material Microbiological Samples .... 17
3.4.4 Microbiological Air Samples 17
4.0 Results and Discussion 18
4.1 Air Samples 18
4.1.1 Total Colony Forming Units 18
4.1.2 Identification of Predominant Fungi 20
4.2 Surface and Bulk Samples 22
4.3 Moisture and Cleanliness 23
5.0 Conclusions and Recommendations 24
6.0 References 26
Appendix A. Microbiological Sampling Raw Data A-1
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FIGURES
Number Page
Figure 1. First Floor Outline Sketch and Sampling Positions 8
Figure 2. Fourth Floor Outline Sketch and Sampling Locations 9
Figure 3. Fifth Floor PCAB Outline Sketch and Sampling Positions 10
TABLES
Number Page
Table 1. Summary of Microbiological Air Samples 13
Table 2, Quality Goals for Critical Measurements 16
Table 3, Mean Total Airborne Fungi and Bacteria in CFU/m3 19
Table 4. Distribution of Predominant Airborne Xerophilic Fungi 20
Table 5. Predominant Xerophilic Fungi Genera Isolated from 4th Floor AHU Fiberglass
Liner, 23
A-1 Raw Data for Xerophilic Fungi A-1
A-2 Raw Data for General Fungi A-2
A-3 Raw Data for Bacteria A-3
A-4 Predominant Airborne General Fungi A-4
A-5 Predominant Xerophilic Fungi Isolated from AHU Condensate Samples ... A-5
A-6 Predominant Genera of Xerophilic Fungi Isolated from Swab Samples of Ceiling
Spaces A-5
A-7 Predominant Dust Xerophilic Fungi Percent A-5
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1.0 BACKGROUND
This research task was a preliminary indoor microbiological screening of the
Polk County Administration Building (PCAB) in Bartow, Florida conducted as part of
CR-817083, Task 11, "Ventilation for Improved Indoor Air Quality." Its goal was to
generate a baseline measurement that could be used, in conjunction with additional
sampling, to evaluate the impact of ventilation system design and operation on the
microbiological aspects of indoor air quality (IAQ). Indoor microbiological
contamination can be a significant cause of poor IAQ, and is known to be associated
with building ventilation systems with some frequency (Woods, 1989.) The impact of a
building's ventilation system on biocontamination is complicated. On the positive side,
building pressurization reduces the infiltration of biocontaminants while maintenance of
relatively dry indoor environmental conditions prevents the growth of the microorganism
spores inside. [Foarde et al. (1992) have shown that biocontaminants will grow and
amplify on building materials at lower moisture levels than previously reported, and the
appropriate level of moisture remains under investigation.] Filtration equipment in the
ventilation systems can similarly reduce the influx of environmental microorganisms
(Foarde et al. 1994.) On the other hand, improperly designed, maintained, or operated
ventilation systems can contribute to indoor biocontamination (Morey and Williams,
1991; Ager and Tickner, 1983.) In addition, the applicability of ASHRAE Standard 62-
1989 to hot and humid climates is being challenged. The increased outdoor air rates
called for in the Standard (necessarily related to building pressurization) are said to
both increase building energy requirements and to lead to increased microbiological
contamination in these climates.
The PCAB was chosen for this screening study primarily because an extensive
study of the building's ventilation system and indoor environment was planned as part
of a radon mitigation study. (This radon research was completely separate from the
present task). During the radon study, the PCAB's indoor environment (temperature,
1
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pressure, and relative humidity) arid HVAC system was characterized on each of the
five floors, and a detailed investigation of the building's air exchange and HVAC
characteristics was conducted.
The PCAB was not thought to have a microbiological problem, and a microbial
investigation was not included in the radon study design. However, a nearby building
of about the same age and having the same owner / operator as the PCAB was known
to have had a very significant microbial contamination problem (Fry, 1994). Thus, the
opportunity existed to incorporate a microbiological screening into the PCAB study at
modest cost, capitalizing on all the characterization work that was already planned for
the radon study. In addition, it was originally thought that the PCAB would be
pressurized to reduce radon infiltration, opening the possibility of investigating the
effects of a change in building pressurization on microbial contamination indoors.
The PCAB has some unfavorable characteristics from the standpoint of a
microbial investigation. The building had 2 or 3 air handling zones per floor, and not all
could be investigated with the resources available. The PCAB also operated under
negative pressure, which had the potential to bring in outdoor microorganisms by
infiltration or through open windows and doors. Infiltration bypasses the HVAC filters,
and tends to confound the meaning of indoor bioaerosol sampling. Indoor
biocontaminant concentrations can vary widely over short periods of time, and the
"grab-sample" nature of indoor bioaerosol samplers makes the results difficult to
analyze, particularly in a screening study. Another difficulty was that changes in the
building operation that were planned for the radon mitigation study might not affect
microbial growth within the time frame of this study. Microbiological investigations are
commonly conducted in problem buildings, and the mere presence of microorganisms
is not an indication of a problem. The indoor and outdoor levels and types of
organisms must be compared to those obtained in other buildings, with the
investigators' judgement weighing heavily in the assessment.
During this study, microbiological data was collected from bulk, surface, and
bioaerosol samples and the moisture content of some building materials was
2
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measured. Each of the measurement types approach the question of biocontamination
from different perspectives, thus addressing the problem of identifying the sources of
biocontamination.
This was a field screening study to evaluate the desirability, according to criteria
given in Section 3.1, of conducting a more complete test at a later date. These criteria
were not met, and further studies are not currently planned.
3
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2.0 BUILDING HVAC SYSTEM
2.1 OVERVIEW OF BUILDING DESIGN
The PCAB, located in Bartow, Florida, is a 5-story, 14,000 m2 (149,000 ft2} brick-
faced building constructed in 1988. It has a permanent occupancy of approximately
300 county employees and elected officials, and also has a large transient population
who come to the building to pay bills, inquire about various aspects of zoning, utilities,
building permits, and to conduct other county business. Bartow is in central Florida
and has the subtropical climate typical of that area.
The footprint of the building is approximately square, and the second floor
encloses about the same amount of area as the first. The third and fourth floors are
set-back, with reduced square floor areas, while the fifth floor area is cross-shaped. All
entrances are from ground level onto the first floor. The principal public entrances are
centered on the north and south sides, and open into a central lobby that is open
vertically to the fourth floor ceiling. Two smaller entrances are located on the east side
of the first floor and two are located on the west side.
In addition to office space and the large lobby, the first floor houses an
auditorium for public meetings. The other floors of the PCAB are devoted largely to
office space and occasional larger meeting / training rooms. An employee lounge on
the north side of the third floor has doors opening to a rooftop terrace. Some of the
PCAB's windows were operable in response to occupant request. None were open in
the rooms that were indoor test sites.
2.2 HVAC SYSTEM DESCRIPTION
The HVAC system in the PCAB utilized variable air volume delivery of
conditioned air and a plenum return. The air was conditioned in chilled water coils
located in variable air volume (VAV) air handling units (AHUs), filtered with 2-in.
ASHRAE-30 filters, then reheated as required for delivery to the space. The air was
4
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distributed to fan-powered VAV terminal boxes. The relative humidity in the building
was controlled to approximately 40 percent. Each floor had multiple HVAC zones. The
first floor of the PCAB had three AHUs and HVAC zones; the other floors had two. The
mechanical rooms were located one above the other, and formed a utilities column on
the east and west walls of the PCAB. All microbiological sampling was conducted on
the first, fourth, and fifth floors, and only those floors are detailed below.
The three HVAC zones on the first floor were partitioned approximately as
follows:
AHU1; Served the main lobby and the first floor auditorium from mechanical room
138.
AHU2: Served both interior and exterior offices on the south side of the first floor.
AHU2 was located in mechanical room 123, which was located in the
southwest quadrant of the PCAB. The outdoor air intake was adjacent to
the mechanical room in the west wall.
AHU3: Served both interior and exterior offices on the north side of the first floor
of the PCAB. AHU3 was located in mechanical room 187, which was
located in the northeast quadrant of the PCAB. The outdoor air intake for
AHU3 was close to the mechanical room in the east wall.
Two HVAC zones were utilized on the fourth floor. The office space was
arranged in a rough square, with the central opening to the atrium lobby normally
closed off with doors.
AHU 8: Served the interior office zone of the fourth floor from mechanical room
454, which was in the southwest quadrant. The outdoor air intake for
AHUS was located in the wall of the mechanical room, facing north.
AHU 9: Served the exterior office zone of the fourth floor from mechanical room
414, which was in the northeast quadrant. This large service area
required that the supply and return ducts from AHU9 encircle the building.
The outdoor air intake for AHU9 was located in the wall of the mechanical
room, facing south.
5
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Two HVAC zones were also utilized on the fifth floor, which was occupied in a
second stage of construction and thus was not numbered consistently with the
remainder of the PCAB. The central opening present on the other floors did not
penetrate through to the fifth floor, whose floor area was a Greek Cross-shaped open-
plan area and not subdivided into small offices. Given the open plan of the fifth floor,
the HVAC systems were not zoned as thoroughly as on the other floors. The HVAC
was arranged in the following manner:
AHU 10: Served the west side of the fifth floor from the (unnumbered) mechanical
room in the southwest quadrant. The outdoor air intake for AHU2 was
located in the wall of the mechanical room, facing south.
AHU 11: Served the east side of the fifth floor from the (unnumbered) mechanical
room in the northeast quadrant. The outdoor air intake for AHU1 was
located in the wall of the mechanical room, facing north.
During the microbiological screening study, the PCAB HVAC system was
operating in its normal daytime operating mode, with all air handlers on and the flows
controlled by the variable volume system.
6
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3.0 EXPERIMENTAL
3.1 INTRODUCTION
This screening study had the express purpose of obtaining enough information
to determine whether a continued investigation of the indoor microbiological levels and
contamination was warranted as part of an investigation of the effects of building
ventilation on microbial contamination. The building would have been recommended
for further study if one of the following conditions existed:
1) Notable microbial contamination was detected in the PCAB, or
2) As a result of the radon mitigation study, the PCAB owner implemented a
change in the HVAC operation that resulted in increased outdoor air or
building pressurization that might affect the microbiological situation in the
PCAB.
Since neither condition was met, the building was not recommended for further
study. Therefore, the results of the screening study have significance principally as a
baseline record of a negatively-pressurized public building in a hot and humid climate.
3.2 PROCEDURES
3.2.1 Overview
The screening study included a building walk-through, outdoor and indoor
bioaerosol sampling, bulk and surface sampling, and occasional building material
moisture measurement. Bulk samples consisted of HVAC fiberglass liner, condensate
i
from drain pans, and composite carpet dust. Surface samples included swabs from
inside selected AHUs and the back side of ceiling tiles. This study was HVAC-system
driven, and the test plan allowed some adjustment of test sites and other aspects of the
study based on conditions in the building. All microbial samples were shipped back to
7
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RTI for analysis.
3.2.2 Test Locations
A walk-through of the entire building to note any visible potential microbial
problems was the first step of the screening study. Observed problems (or potential
problems) affected the study locations, which were generally planned to coincide with
those where the environmental parameters were measured for the radon study. Each
indoor bioaerosol sampling site was paired with an outdoor bioaerosol sampling site;
that is, the outdoor site was near the outdoor air intake to the air handler serving the
zone of the indoor site. Applying these criteria, the majority of the screening samples
were collected in the following locations:
1) Room 170, which was in the northeast quadrant of the PCAB first floor,
and part of the building exterior HVAC zone served by AHU3. The
general location of all of the first floor sampling sites is shown in Figure 1.
t
Room 170
Microbial
T1 Sampling
*
North
1st Floor NE
167 Outdoor Air
Mechanical
Room, AHU3
Sampling
Site
Mechanical
Room,AHU2
Central
Atrium
1st Floor SW
Outdoor Air
Sampling
Site
Figure 1. First Floor Outline Sketch and Sampling Positions.
8
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2) Outdoors, approximately 1.5 m above ground level on the northeast
comer of the PCAB near the outdoor air intake for AHU3.
3) Room 138A, in the southwest quadrant of the first floor, and in the interior
HVAC zone of the PCAB served by AHU2.
4) Outside, approximately 1.5 m above ground level on the southwest
quadrant of the PCAB near the outdoor air intake for AHU2.
5) Room 413, in the northeast quadrant of the PCAB fourth floor, and part of
the fourth floor's exterior HVAC zone served by AHU9, The general loca-
tion of each of the fourth floor sampling sites is shown in Figure 2.
4th Floor
SW OA
Sampling Site
(at 3rd ~-
Floor Level)
Mechanical
Room, AHU8
454
t
Room 413
Microbial
Sampling
North
m
Room 440
Microbial
Sampling
4th Floor NE
OA Sampling Site
(4th Floor Roof)
/
414
Mechanical
Room, AHU9
Figure 2. Fourth Floor Outline Sketch and Sampling Locations.
6) Outside on the fourth floor roof, approximately 3 m above and 4 m north
of the fourth floor air intake for AHU9. This sample site was at the same
level and approximately 2 m north of the air intake for the fifth floor air
handler, AHU11.
7) Room 440, in the southwest quadrant of the PCAB fourth floor, and part of
the fourth floor interior HVAC zone served by AHU8.
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8) Outside on a ledge on the west side of the PCAB, approximately 2,5 m
below and 4 m north of the fourth floor air intake for AHU8 and inside the
shelter formed by the building's architecture on the west side,
9) In the northeast quadrant of the fifth floor open office space generally
served by AHU11 as shown in Figure 3. The outdoor air for AHU11
entered near the outdoor air sample site on the fourth floor roof described
under item 6, above.
Figure 3. Fifth Floor PCAB Outline Sketch and Sampling Positions.
3.2.3 HVAC System Sampling
The HVAC systems serving the test zones were inspected for visible problems
(standing water, plugged condensate drains, duct leaks, etc). Where appropriate,
surface microbial samples and material moisture measurements were obtained from the
outdoor air duct wall, the upstream duct wall, filter, downstream duct wall, and
4th Floor NE and
5th Floor Outdoor
Air Sampling Site
North
*
Microbial
Sampling
Site
Mechanical
Room
10
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condensate pan. HVAC system samples were taken and analyzed to assess their
potential for microbial contamination.
3.2.4 Indoor Environment Evaluation
3.2.4.1 Cleanliness-
Cleanliness near the air sampling regions was evaluated qualitatively by
inspection and noted on the data sheet by location. Notes concerning building cleanli-
ness were also made during the walk-through. Swab samples were collected at some
locations to qualitatively assess microbial flora. No quantitative evaluations were made
with swab samples.
3.2.4.2 Material Moisture fConductivitvV-
Building material moisture content was evaluated using a conductivity meter
internally calibrated and set on the concrete and plaster scale. The readings are
relative and the instrument was intended to identify any moist locations that might be
microbial reservoirs or have the potential to become microbial sources. Moisture
evaluations were made at various locations deemed appropriate during the walk-
through, and for the HVAC materials. The location of each measurement was noted in
the project notebook. The Delmhorst Model BD-8 Moisture Meter was calibrated before
initial reading by pressing the "CAL CHK" button and confirming that the meter read 20.
The short-pronged electrodes of the moisture meter were carefully inserted
approximately 14 inch into the material to be tested. The "READ" button was then
depressed and held down until the reading stabilized. The moisture level was read off
the "plaster/concrete" scale. Duplicate readings were taken at all locations.
3.2.5 Biocontaminant Sampling
3.2.5.1 Surface and Bulk Material Sampling-
Swab surface and bulk material samples were collected at appropriate locations
to assess microbial flora within the PCAB. The locations were identified during the
walk-through. Some were within the HVAC systems. The location of each sample was
11
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noted in the project notebook.
Swab samples were collected with sterile swabs which were wiped across the
surface to be tested. The swabs were then transferred to sterile 15 ml centrifuge tubes,
sealed and placed into resealable plastic bags. Ten to 50 ml samples of condensate
from the drain pans were pipetted directly into sterile containers which were sealed and
placed into resealable bags. Similarly, HVAC fiberglass liner was collected and placed
directly into resealable bags.
Floor surface dust was sampled on the first and fourth floors using the Oreck®
XL, Super Buster B, Compact Canister D vacuum with XL Double Wall filter bag
reported to contain particles down to 1 .Oum. A new bag was used for each sample.
Before use and between samples the machine was cleaned by removing the faceplate,
hose adaptor, and all attachments used for sampling. Inner surfaces were rinsed and
brushed with clean hot water followed by a 70% ethanol rinse. Clean gauze wrapped
around a brush was used to wipe the inside surfaces, followed by air drying when
necessary. After sample collection, the entire bag was removed, the opening taped
shut, and the vacuum bag placed in a resealable plastic bag.
3.2.5.2 Bioaerosol Samplina--
Both indoor and outdoor air sampling utilized the same sampling instruments.
All sampling was conducted in temporarily vacated offices or after work hours to avoid
disturbing the PCAB occupants. Indoor air samples were obtained with Mattson-Garvin
slit-to-agar samplers operated over 30-minute periods at each test site, and outdoor air
samples were also obtained with a Mattson-Garvin using a 5-minute sampling period.
The Mattson-Garvin sampler draws air at 28.3 Urn in through a 0.15 mm slit allowing a
broad range of airborne particles to be impacted upon the surface of a 150 mm rotating
agar plate. The sampler was disinfected with 70% ethanol before the initial sampling
and each time the test location was changed. Table 1 presents a list of all the
microbiological air samples taken. All samples were taken in duplicate sequentially.
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Table 1. Summary of Microbiological Air Samples.
Location
Sample
Duration
(min.)
Number of Runs with each Media
Fungi
Bacteria
General
Xerophilic
Room 170, inside NE
30
2
2
2
First Floor outside, NE
5
2
2
2
Room 138A, inside SW
30
2
2
2
First Floor outside, SW
5
2
2
2
Room 413. inside NE
30
2
2
2
Fifth Floor outside, NE
5
2
2
2
Room 440, inside SW
30
2
2
2
Third Floor outside, SW
5
2
2
2
Fifth Floor inside, NE
30
2
2
2
Control runs
5
1
1
1
Media Blanks
NA
0
1
0
Total Plates Evaluated
19
2
19
A complete set of samples from each of the nine locations described in Section
3.2.2 consisted of sequential duplicate fungi samples for each of two media, and
sequential duplicate bacteria samples for one media. A total of 54 Mattson-Garvin
samples were obtained. Three Mattson-Garvin control runs were made, one with each
media, as QA/QC for the sampler procedure. One fungal media blank was taken. After
sample collection at PCAB, all samples were taped closed, wrapped with packing
material, placed in sealed insulated containers containing ice, and shipped for delivery
to the RTI laboratory within 24 hours.
3.2.5.3 Media Preparation and Sample Processing-
Three media were chosen for use in this microbiological screening. All samples
-- air, bulk and surface -- were processed using these same media. Trypticase soy
agar (TSA) was employed for the isolation and enumeration of both mesophilic and
13
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thermophilic bacteria. TSA is a general purpose media developed for the isolation and
cultivation of fastidious and non-fastidious organisms. Two different media were
employed for the isolation of fungi -- Sabouraud dextrose agar (SDA) and diehloran
glycerol agar (DG18). SDA is a general purpose media developed for the isolation and
cultivation of fastidious and non-fastidious fungi (molds and yeasts). DG18 is a media
developed for the isolation of xerophilic fungi. Xerophilic organisms are those that are
able to grow under very low water conditions. Many members of the genera Aspergillus
and Penicillium are xerophiles.
All media used in this study were prepared in the RTI laboratories. All
commercial, dehydrated media components and reagents were inspected, dated, and
stored appropriately upon receipt. Ingredients were weighed on calibrated, laboratory
balances and suspended in distilled, deionized 18 megohm water. Sterilization was
conducted in a steam autoclave operating at 121 °C and 100 kPa. All media was
incubated following preparation to insure sterility, with representative samples
inoculated with known fungi and bacteria as growth controls. Organisms used included
Aspergillus versicolor, Penicillium glabrum, Staphylococcus aureus, Escherichia coli,
and Bacillus stearothermophilis. All media was inspected before use, and discarded if
found to be contaminated. Field media blanks were also utilized on-site in conjunction
with the Mattson/Garvin bioaerosol samplers.
3.2.5.4 Sample Processing -
Upon receipt of the samples at the RTI laboratory, they were checked in, entered
into the sample tracking system, and processed. Mattson-Garvin plates were
incubated at 25°C for molds and 32°C for bacteria. Surface swabs were suspended in
5 ml of phosphate-buffered saline (FTAb), vortex mixed for 1 minute, and diluted 1:10.
Aliquots of 0.1 ml of the undiluted and the diluted sample were plated in duplicate on
each of the 3 recovery media. An additional TSA plate incubated at 55°C (for
thermophiles) was only inoculated with the undiluted sample. Condensate was diluted
1:10 and plated out like the surface swabs. Duct insulation was weighed first and the
weights recorded before being suspended in 5 ml of FTAb and processed like the
14
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previous samples. In the laboratory, each composite carpet dust sample was weighed,
sieved (250 //m), and thoroughly mixed, after which 0.5 g samples of the smaller than
250 pm dust were suspended in 10 ml of FTAb, vortex mixed and diluted 1:10 and
1:100, with 0.1 m! aliquots of both dilutions plated in duplicate on the three recovery
media. Duplicate additional TSA plates were plated with 0.1 ml aliquots of the
undiluted sample and incubated at 55°C for thermophiles. Following inoculation, all
samples were incubated like the Mattson-Garvin plates. Mold samples were grown
under alternating conditions of fluorescent light and darkness for at least 10 days.
Identification of isolated fungi was based on colony morphology, pigmentation, and
microscopic examination, in accordance with standard reference texts and reference
cultures from RTI's environmental microorganism culture collection. Bacteria samples
were incubated 3-5 days. Identification of isolated bacteria was based on colony
morphology, pigmentation, microscopic examination, and biochemical testing as
needed, in accordance with standard reference texts and reference cultures from RTI's
environmental microorganism culture collection.
3.3 DATA QUALITY INDICATORS
This program was a screening study, and as such the purpose of the
measurements were generally qualitative rather than quantitative. Surface samples (for
moisture or microbial contamination) were made at selected sites within the building,
and these sites were generally selected to have a relatively high potential for microbial
contamination (i.e., wet spots, collected dirt on the floor or carpet, likely locations for
condensation). In all these cases, microbial contamination is highly site-specific, and
the variance from site-to-site is much larger than the measurement error. Swabbed
surface areas vary for each sample, and are not comparable for the broad range of
surfaces encountered during this screening study. The swab surface samples are
qualitative. Microbial growth was identified to the genus-level, with occasional semi-
quantitative evaluations of organism levels in specific, comparable locations.
15
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The same general concerns about the routine variability of indoor bioaerosol
levels apply to the air samples, though the air samples were quantitative. The
presence of microorganisms in the air does not necessarily indicate that a building is
contaminated, and their absence does not necessarily indicate that it is not
contaminated. A combination of factors must be considered. The primary indications
of a problem will be observation of a significant amplification site (for instance, visible
growth on a surface coupled with elevated indoor levels of the same organism) or a
difference in the distribution of microbial flora from outdoor to indoor. Within this
context, data quality indicators for the measurements are given in Table 2. The
microbial samplers used during this screening study readily met these DQIs.
Table 2. Quality Goals for Critical Measurements
Measurement
Reference
Method
Precision
Accuracy
Moisture by Conductivity
Gravimetric
± 5%
±10%
Mold presence on
surface*
Not Available
Not Applicable
Not Applicable
Mold presence in air*
Not Available
± 10 fold
Not Applicable
Visual determination of predominant genus, only.
3.4 QUALITY ASSURANCE
3.4.1 Cleanliness
Cleanliness was a qualitative evaluation, and no measurements were associated
16
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with that assessment.
3.4.2 Material Moisture
QA/QC for the measurement is described in Section 3.2.4.2. This
measurement was seldom used at the PCAB because only in a single case was visible
evidence of interior moisture observed, and the water-marked material in question gave
a material moisture reading below the detection limit of the instrument. Therefore, no
material moisture results are reported.
3.4.3 Surface and Bulk Material Microbiological Samples
QA/QC for the surface and bulk material microbial samples consisted primarily of
control plates and samples that were subjected to the entire analysis procedure but
never exposed to the environment being sampled, These controls were all negative
indicating the collection procedures were satisfactorily performed.
3.4.4 Microbiological Air Samples
QA/QC for the microbiological air samples consisted primarily of control
samples. One control sample of each media was exposed during the test period. This
control run consisted of preparing the sampler following standard procedures, placing
the media in the sampler, attaching a HEPA filter capsule to the Mattson-Garvin inlet,
and conducting a 5-minute test run. The control runs provided a final check to establish
the effectiveness of the disinfection procedures used between runs. The control
Mattson-Garvin runs obtained during this preliminary screening study did not indicate
any systematic error in the sampling procedure.
17
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4.0 RESULTS AND DISCUSSION
4.1 AIR SAMPLES
As described above, sequential duplicate air samples were collected for both
bacteria and fungi; and the fungi were collected on two different media, one general
purpose media and one primarily for the isolation of xerophilic molds. The results are
summarized below, and tables containing the data from the individual duplicate runs
(including the means and standard deviations) for the xerophilic and overall fungi as
well as the bacteria are included in Appendix A. A comparison of the results from the
two fungal media (SDA, or general purpose, and DG18, for xerophilic organisms)
demonstrated very little difference in the numbers of CFU/m3 or distribution of
organisms; therefore, this discussion will be confined to only the results from the
xerophilic media.
4.1.1 Total Colony Forming Units
Table 3 presents a summary of the mean levels of CFUs/m3 for the xerophilic
fungi and the bacteria at each of the nine sites sampled. Multiple outdoor locations
were sampled and the data in the table are arranged so that the results of the outdoor
air sampling is directly above the corresponding indoor sample. For example, on the
first floor both the northeast and southwest zones were sampled. Room No. 170 was
located in the northeast zone so the results in the table are paired with the outdoor
results for the northeast. For the fourth floor northeast zone inside sample, the fifth
floor outside sample is the corresponding sample.
18
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Table 3. Mean Total Airborne Fungi and Bacteria in CFU/m3.
Location
Room
Xerophilic Fungi
Bacteria
1st floor NE
Outdoor Air
1100
520
1st floor NE
Room 170
610
330
1 st floor SW
Outdoor Air
580
1900
1st floor SW
Room138A
110
270
4th floor NE*
Outdoor Air
530
250
4th floor NE*
Room 413
210
80
4th floor SW
Outdoor Air
830
440
4th floor SW
Room 440
80
190
5th floor NE*
Outdoor Air
530
250
5th floor NE*
Inside
30
30
* The Outdoor Air sample collected on the 5th floor NE was paired with both the 5th floor
inside sample and the sample collected In Room 413 because it was near both the 4th and
5th floor outdoor air intakes.
A comparison of the outdoor and indoor mean levels shows that for all the pairs
there were less organisms isolated indoors than out. This result is consistent with that
found in a non-problem building. An examination of the data for the individual samples,
shown in Tables A-1, A-2 and A-3 of Appendix A, confirms that result for most of the
sampling locations. However, for Rooms 170 and 413 there are considerable
differences between the results on both of the fungal media for the two sequential
duplicates. The first run in Room 170 for xerophilic organisms yielded 155 CFUs/m3,
while the second isolated 971 CFUs/m3 (Table A-1). Similar results were obtained on
the general purpose media (Table A-2). A less dramatic but equally noteworthy
difference was seen in the samples collected in Room 413. This difference between
sequential duplicate sampling runs in the same room requires further examination of
the data, specifically the identification of the organisms that may be responsible for the
variation measured.
19
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4,1.2 Identification of Predominant Fungi
Table 4 shows the percentage breakdown for the three most commonly isolated
molds (xerophilic media) for each of the duplicate samples from each site. The
sampling results employing the general purpose media are found in Table A-4 in
Appendix A, and again confirm the results seen with the xerophilic media.
Table 4. Distribution of Predominant Airborne Xerophilic Fungi.
Location
Room
Fungi
Cladosporium
Periicillium
Aspergillus
1st floor NE
Outdoor Air
64
11
0
72
6
0
1st floor NE
Room 170
55
7
3
43
28
28
1st floor SW
Outdoor Air
68
6
0
79
4
0
1st floor SW
Room138A
16
48
0
39
20
0
4th floor NE*
Outdoor Air
71
11
1
61
8
0
4th floor NE*
Room 413
73
14
1
26
67
1
4th floor SW
Outdoor Air
59
24
1
NA
NA
NA
4th floor SW
Room 440
42
12
2
39
25
7
5th floor NE*
Outdoor Air
71
11
1
61
8
0
5lh floor NE*
Inside
33
43
5
29
38
10
* The 5th floor NE outdoor air sample was also paired with the 4th floor NE indoor sample
because it was the accessible location closest to the 4th floor NE AHU outdoor air intake.
20
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In many regions of the world, the molds most commonly isolated outdoors
belong to the genus Cladosporium (Seller, 1984). As can be seen in Table 4,
Cladosporium spp. predominated in all the outdoor samples, with over 50% of the total
CFUs identified as belonging to that genus. The second most commonly isolated mold
in the outdoor air was Penicillium. In all cases outdoors, less than 25% of the total
colonies were identified as Penicillium spp.
It is generally expected that the numbers and distribution of indoor airborne fungi
in mechanically ventilated non-problem buildings will reflect those found in the
outdoors, but at lower levels. As with the outdoor samples, in most of the indoor
sampling locations in the Polk Administration Building, Cladosporium was the
predominant genus followed by Penicillium. In four out of five indoor locations and two
out of four outdoor locations, there were a few Aspergilli isolated.
As discussed in Section 4.1.1, the levels of total fungi isolated in the duplicate
samples for each of rooms 170 and 413 were noticeably different. In addition, there
was a change in the distribution of the predominant fungi. As can be seen in Table 4,
in Room 170 there was an increase in the percentage of Penicillium isolated. In the
first sample only 7 percent of the total fungi were Penicillium; however, in the replicate
28 percent were Penicillium. For the first sample taken in room 413, 14 percent of the
total fungi were Penicillium, while in the second 67 percent were Penicillium. The
results from both rooms give some cause for concern, but for different reasons. The 28
percent Penicillium spp. isolated from Room 170 in itself might not be excessive.
However, there was also a 10-fold increase in total Penicillium counts between the first
and second samples, from 11 CFU/m3 to 272 CFU/m3. In the same samples, the
airborne concentrations of Aspergillus spp. also increased. Combined, these data
suggest that additional investigation might be warranted. The sample plates gave no
evidence of being anomalous, and the results may be significant. In the case of Room
413, while the counts on the second replicate increased, the total CFU/m3 were only
332 and therefore are not necessarily excessively high. However, the fact that 67% of
those were Penicillium suggests further investigation may also be advisable. Again, the
21
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sample plates gave no evidence of being anomalous. Although airborne fungal
measurements are grab samples and subject to considerable variability, in both of
these rooms the increase in total counts was detected by two different samplers on two
different media at the same time. An increase in the fraction of Peniciliium was
confirmed in Room 413 by both media. For the samples collected in Room 170, an
increase in the fraction Peniciliium was detected on the xerophiiic media (DG18).
However, the second run on the general purpose media was overgrown and the actual
number of Peniciliium colonies could not be counted, though the results were not
contradictory. These results indicate that there may be potential source reservoirs of
Peniciliium contaminating the rooms.
4.2 SURFACE AND BULK SAMPLES
A number of different surface and bulk samples were collected -
condensate from drain pans, swabs of ceiling tiles and AHUs, bulk samples of
fiberglass liner, and composite carpet dust. The complete xerophiiic fungi results for
the bulk condensate and composite dust samples are presented in Tables A-5 and A-7
in Appendix A. The ceiling tile swab data is in Table A-6 in Appendix A. None of these
samples showed any remarkable levels or distribution of organisms, either bacterial or
fungi.
The other bulk samples, fiberglass liner from the 4th floor AHU and swab
samples from the 1st floor southwest AHU and the 4th floor northeast AHU, yielded
potentially significant numbers of Peniciliium in practically pure culture. Table 5
presents the results of the analysis of the wet and dry fiberglass insulation samples.
22
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Table 5. Predominant Xerophilic Fungi Genera Isolated from 4th Floor AHU
Fiberglass Liner.
Location
CFU/gram
Fungi, %
Cladosporium
Penicillium
Aspergillus
WET
1.2 X103
0
100
0
DRY
7.7 X 10s
8
92
0
Swab samples of a small patch of white mycelial-like material were taken in
AHU2 located on the 1st floor (southwest) and AHU9 located on the fourth floor
(northeast). Analysis showed a pure growth of Penicillium. Isolation of Penicillium
species from both the AHU swabs and the fiberglass liner suggest that possible source
reservoirs may have been identified. Although speciation of the Penicillium was not
performed, isolation of the colonies in some of the AHUs is consistent with the
evidence of potential contamination suggested by the elevated air sampling replicates,
though it does not confirm that the AHUs are the source reservoir.
4.3 MOISTURE AND CLEANLINESS
Moisture meter readings were taken at a variety of locations within the building.
Only one potential water stain was identified during inspection of the building. No
readings above 0 were measured. Cleanliness was also determined visually. Overall,
the impression of the building was that of a clean, well-maintained facility. Swab
samples were taken when potential biocontaminant sources were identified. These
results have already been discussed.
23
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5.0 CONCLUSIONS AND RECOMMENDATIONS
The overall impression of the Polk County Administration Building was of a
clean, well-maintained, low occupancy structure. The majority of the microbiological
screening results were consistent with those of non-problem buildings (Cole et al,
1994). The combined results of the air, bulk, and surface sampling did not indicate a
clear biocontaminant problem In the building. On the other hand, the sampling period
was short and samples were taken in only a few locations. The elevated airborne
levels for one of two sequential airborne fungi samples in each of two different rooms
(confirmed by the second fungal media), coupled with the isolation of essentially pure
Peniciilium in some of the AHUs, gives some cause for concern. Considering that the
building is located in a hot, humid climate, that biological contamination problems have
occurred in adjacent buildings, and that some occupants may have been sensitized to
fungal contamination, further investigation for potential source reservoirs might be
prudent.
The overall question to which the study was addressed -- the impact of a
building's ventilation system on microbial contamination -- could not be investigated in
the PCAB beyond the baseline level. No ventilation modifications that were expected
to be microbiologically: significant were planned for the building at the time the project
was completed. The PCAB is negatively;pressurized and appears to have restricted
outdoor air intakes. Infiltration air is therefore unfiltered and unconditioned, and the
potential exists for transport of biocontaminants in the infiltrating air, for condensation
of water vapor in infiltration paths, and consequent building contamination. On the
other hand, the PCAB is operated at a low relative humidity that tends to prevent
microbial growth, though it is presumably expensive to operate. This combination of
characteristics presents a number of research opportunities:
1) The results of this screening study are not conclusive to either identify the PCAB
as a biocontaminated problem building or to clearly show that biocontamination
24
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is not an issue in the PCAB. The study was not designed to accomplish that
task. The results do show that fungi (Penicillium spp.) have become established
in some AHUs and are either established in some parts of the ventilation system
downstream of the filters or are at least occasionally transported through the
filters to some rooms at levels above those found in most PCAB indoor locations
and roughly equivalent to outdoor levels. The building may be in transition from
non-problem to problem, and as such presents an unusual opportunity to study
some important questions, such as: a) How extensive is the HVAC system
contamination?, b) What conditions led to that contamination?, c) Is PCAB
becoming a problem building and is the contamination getting worse?, and d)
Can conditions be modified to prevent a serious contamination problem from
developing?
The PCAB could be modified physically to operate at a controlled positive
pressure to ensure that air entering the building was conditioned. This would
require both duct and control modifications. Both short- and long-term studies of
the microbial ecology in the building would provide valuable information
concerning the impact of building pressurization in a hot and humid climate.
In combination with pressurization, a reduced-energy operating mode could be
designed for the PCAB to, potentially, provide both reduced costs and reduced
microbial contamination potential.
In addition to building pressurization, the impact of building ventilation rates on
microbial contamination and general indoor air quality could be studied by
modifying the outdoor air intakes to allow increased outdoor air delivery. Such
operation should be optimized for energy efficiency consistent with prevention of
conditions conducive to microbial growth in the building.
-------
6.0 REFERENCES
Ager, B.P., arid J.A. Tickner. 1983. The Control of Microbiological Hazards Associated
with Air-Conditioning and Ventilation Systems. Ann. Occup. Hyg. 27(4):341-
358.
ASHRAE. 1989. ASHRAE Standard 62-1989: Ventilation for Acceptable Indoor Air
Quality. American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc. Atlanta, GA.
Cole, E. C. et al. 1994. Assessment of fungi in carpeted environments. In: Health
Implications of Fungi in Indoor Environments, R. A. Samson et al., eds. Elsevier,
New York, NY, pp. 103-128.
Foarde, K., D. Bush, E. Cole, D. Franke, D. VanOsdell, and J. Chang. 1992.
Characterization of Environmental Chambers for Evaluating Microbial Growth on
Building Materials. In IAQ '92: Environments for People, San Francisco, CA,
October 19-21, 1992. pp. 185-190.
Foarde, K. K., D. W. VanOsdell, J. J. Fischer, and K. E. Leese. 1994. Investigate and
Identify Indoor Allergens and Biological Toxins that Can Be Removed by
Filtration. Final Report to ASHRAE RP-760. American Society of Heating,
Refrigerating and Air-Conditioning Engineers, Inc. Atlanta, GA.
Fry, J. What's Gone Wrong? 1994. Indoor Air Review. November, 1994. pp. 12-13.
Morey, P.R., and C.M. Williams. 1991. Is Porous Insulation Inside an HVAC System
Compatible with a Healthy Building? In IAQ'91: Healthy Buildings, Washington,
DC, September 4-8, 1991, pp. 128-135.
Seller, M. R. 1984. Mould Allergy and Climate Conditions. Mould Allergy. Al-Doory
and J. F. Dawson, Eds. Lea and Febiger Publishers. Philadelphia, PA.
Woods, J.E. 1989. HVAC Systems as Sources or Vectors of Microbiological Contami-
nants. Presented at the CPSC/ALA Workshop on Biological Pollutants in the
Home, Alexandria, VA, July 10-11, 1989, pp. C-68 to C-75.
26
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APPENDIX A. MICROBIOLOGICAL SAMPLING RAW DATA
TABLE A-1. RAW DATA FOR XEROPHILIC FUNGI
Location
Room
CFU/m3
Mean
Standard
Deviation
1st floor NE
Outdoor Air
1187
1095
130
1004
1st floor NE
f""k J mmm
Room 170
155
563
576
971
1 st floor SW
Outdoor Air
551
580
40
608
1 st floor SW
Room138A
120
113
10
106
4th floor NE"
Outdoor Air
495
530
50
565
4th floor NE
Room 413
92
212
170
332
4th floor SW
Outdoor Air
827
827
NA
NA
4th floor SW
Room 440
98
75
32
52
5th floor NE
Outdoor Air
495
530
50
565
5th floor NE
Inside
25
25
0
25
The 4th floor NE outdoor air sample was the same as the 5th floor NE
outdoor air sample.
A-1
-------
TABLE A-2. RAW DATA FOR GENERAL FUNGI
Location
Room
CFU/m3
Mean
Standard
Deviation
1st floor NE
Outdoor Air
1110
901
295
693
1st floor NE
Room 170
111
1191
1527
2271
1st floor SW
Outdoor Air
664
643
30
622
1st floor SW
Room138A
86
74
17
61
4th floor NE"
Outdoor Air
410
456
65
502
4th floor NE
Room 413
61
147
121
232
4th floor SW
Outdoor Air
749
710
55
671
4th floor SW
Room 440
77
65
16
54
5th floor NE
Outdoor Air
410
456
65
502
5th floor NE
Inside
32
32
1
33
The 4th floor NE outdoor air sample was the same as the 5th floor NE
outdoor air sample.
A-2
-------
TABLE A-3. RAW DATA FOR BACTERIA
Location
Room
CFU/m3
Mean
Standard
Deviation
1st floor NE
Outdoor Air
318
523
290
728
1st floor NE
Room 170
Overgrown
325
Not Avail.
325
1 st floor SW
Outdoor Air
2688
1898
1114
1110
1st floor SW
Room 138A
265
266
2
267
4th floor NE"
Outdoor Air
240
254
20
37
4th floor NE
Room 413
79
84
7
90
4th floor SW
Outdoor Air
657
435
315
212
4th floor SW
Room 440
241
192
70
143
5th floor NE
Outdoor Air
240
254
20
37
5th floor NE
Inside
29
33
5
25
The 4th floor NE outdoor air sample was the same as the 5th floor NE
outdoor air sample.
A-3
-------
TABLE A-4. PREDOMINANT AIRBORNE GENERAL FUNGI
Location
Room
Fungi, Percent of Total
Colonies
Cladosporium
Penicillium
Aspergillus
1st floor NE
Outdoor Air
68
6
1
64
8
0
1st floor NE
Room 170
54
7
0
NA
NA
NA
1 st floor SW
Outdoor Air
68
6
0
59
0
1
1st floor SW
Room 138A
27
38
0
23
27
2
4th floor NE*
Outdoor Air
57
5
0
51
8
3
4th floor NE
Room 413
37
25
0
17
60
2
4th floor SW
Outdoor Air
50
25
25
53
14
14
4th floor SW
Room 440
32
15
2
28
26
0
5th floor NE
Outdoor Air
57
5
0
51
8
3
5th floor NE
Inside
33
33
4
25
29
0
NA results not available due to overgrowth of plate with Rhizopus.
* The 4th floor NE outdoor air sample was the same as the 5th floor
NE outdoor air sample.
A-4
-------
TABLE A-5. PREDOMINANT XEROPHILIC FUNGI ISOLATED
FROM AHU CONDENSATE SAMPLES
Location
CFU/ml
Fungi, Percent of Total Colonies
Cladosporium
Penicillium
Aspergillus
1st floor SW
40
0
0
0
4th floor NE
20
0
0
1
5th floor NE
230
0
0
0
TABLE A-6. PREDOMINANT GENERA OF XEROPHILIC FUNGI ISOLATED
FROM SWAB SAMPLES OF CEILING SPACES
Location
CFU/sample
Fungi, Percent of Total Colonies
Cladosporium
Penicillium
Aspergillus
4th floor
3
34
0
50
4th floor NE
25
52
8
8
5th floor
47
24
2
7
1st floor
18
29
13
23
TABLE A-7. PREDOMINANT DUST XEROPHILIC FUNGI PERCENT
Location
CFU/a
Fungi, Percent of Total
Colonies
Cladosporium
Penicillium
Aspergillus
1st floor
2.3 X 105
9
17
4
4th floor
1,5 X 105
29
9
8
A-5
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