Assessment of Mold and 

Indoor Environmental 

Quality in a Middle 

School – Texas

Nancy Clark Burton, PhD, MPH, CIH

John Gibbins, DVM, MPH

Health Hazard Evaluation Report

HETA 2008-0151-3134

July 2011

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

Workplace

Safety and Health

 National Institute for Occupational 

Safety and Health

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific 

facility evaluated and may not be universally applicable. Any recommendations made are not to be 

considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE 

reports are available at http://www.cdc.gov/niosh/hhe/
The employer shall post a copy of this report 

for a period of 30 calendar days at or near 

the workplace(s) of affected employees. The 

employer shall take steps to insure that the 

posted determinations are not altered, defaced, 

or covered by other material during such 

period. [37 FR 23640, November 7, 1972, as 

amended at 45 FR 2653, January 14, 1980].
Health Hazard Evaluation Report 2008-0151-3134 Page i

Report Abbreviations................................................................................................ii

Highlights of the NIOSH Health Hazard Evaluation........................iii

Summary .........................................................................................................v

Introduction ...................................................................................................1

Assessment.....................................................................................................2

Results..............................................................................................................3

Discussion.......................................................................................................7

Conclusions....................................................................................................8

Recommendations.......................................................................................8

References.................................................................................................... 10

Contents

Acknowledgments

Appendix A

Appendix B 

Indoor Environmental Quality Graphs............................................... 11

Occupational Exposure Limits and Health Effects......................... 15

Acknowledgments and Availability of Report................................ 20
Page ii Health Hazard Evaluation Report 2008-0151-3134

Abbreviations

ACGIH® American Conference of Governmental Industrial Hygienists

AIHA American Industrial Hygiene Association

ANSI American National Standards Institute

ASHRAE American Society of Heating, Refrigerating, and Air-Conditioning Engineers

CDC Centers for Disease Control and Prevention

CFM Cubic feet per minute

CFR Code of Federal Regulations

CO2 Carbon dioxide

CO Carbon monoxide

HHE Health hazard evaluation

HVAC Heating, ventilating, and air-conditioning

IEQ Indoor environmental quality

IOM Institute of Medicine

Ls-1 Liters per second

NAICS North American Industry Classification System

NIOSH National Institute for Occupational Safety and Health

OEL Occupational exposure limit

OSHA Occupational Safety and Health Administration

PEL Permissible exposure limit

ppm Parts per million

RH Relative humidity

U.S. EPA United States Environmental Protection Agency

VOC Volatile organic compound

WHO World Health Organization
Health Hazard Evaluation Report 2008-0151-3134 Page iii

The National Institute for 

Occupational Safety and 

Health (NIOSH) received a 

management request for 

a health hazard evaluation 

at a middle school in 

Texas, which we had 

evaluated a year earlier. 

The request was to look at 

the indoor environmental 

quality (IEQ) at the school 

after mold remediation 

and remodeling had been 

completed.

Highlights of the

NIOSH Health

Hazard Evaluation

What NIOSH Did

● We visited the school on April 22–24, 2008.

● We talked to employees about their health.

● We measured carbon dioxide (CO2), carbon monoxide, 

temperature, and relative humidity (RH) in the school 

throughout the day on April 23, 2008.

● We collected sticky tape samples from surfaces to look for 

mold growth.

● We used thermal detection to look at temperature differences 

around window frames in the classrooms.

● We reviewed reports from previous environmental sampling.

● We talked about the results of an investigation done by the 

city health department that looked at student health issues.

What NIOSH Found

● The CO2 levels in three classrooms were higher than 

recommended guidelines. This finding means there may be 

a problem with enough outdoor air being supplied to the 

classrooms.

● The air temperatures in the classrooms were lower than what 

is recommended as a comfortable level for indoor working 

environments.

● The RH levels in the classrooms were higher than what is 

recommended as a comfortable level for indoor working 

environments.

● The windows did not completely close at the time of our 

evaluation, so humid air could enter the building. All 

windows were replaced later in 2008.

● Small amounts of mold growth were found under wooden 

furniture and in the hallways.

● Complaints by staff about health symptoms have decreased 

following remodeling and mold remediation.

What Managers Can Do

● Provide at least the minimum recommended amount of 

outdoor air to the classrooms and library to reduce CO2

levels. These recommendations are made by the American 

National Standards Institute and the American Society of 

Heating, Refrigerating, and Air-Conditioning Engineers.
Page iv Health Hazard Evaluation Report 2008-0151-3134

Highlights of the

NIOSH Health

Hazard Evaluation

 (continued)

● Follow current comfort guidelines for temperature and RH 

in the school. These guidelines are set by the American 

National Standards Institute and the American Society of 

Heating, Refrigerating, and Air-Conditioning Engineers.

● Inform employees and students about what is being done 

to address IEQ problems and why these changes are being 

made.

● Start an IEQ management program.

What Employees Can Do

● Get medical care for symptoms potentially related to your 

work. See a healthcare provider who is knowledgeable in 

occupational medicine and IEQ issues.

● Report any concerns you have about the work environment 

to management so they can address these issues.
Health Hazard Evaluation Report 2008-0151-3134 Page v

The school district 

had made many of the 

changes we and others 

had recommended. 

However, high humidity 

levels in the school 

remained and led to 

the recurrence of mold 

growth. We recommend 

that management modify 

the ventilation systems 

to ensure that IEQ 

parameters meet current 

guidelines and establish 

an IEQ management 

program.

Summary

In March 2008, NIOSH received an HHE request from management at 

a middle school in Texas concerning a history of mold contamination. 

NIOSH had conducted an HHE at this school in September 2007; the 

school was closed from September 2007 until March 2008 for repairs 

and mold remediation. NIOSH was asked to conduct a follow-up 

evaluation to look at the current IEQ conditions at the school.

In April 2008, we visited the school and looked at building conditions. 

We met with management and employees to discuss current issues. 

We measured CO2, CO, temperature, and RH; used thermal imaging 

to look at temperature gradients; and collected sticky tape samples on 

furniture and ceiling surfaces to look for mold growth. At the request 

of the school district, the city health department conducted a parallel 

investigation to evaluate health concerns among the students.

We found that management had addressed many of the problems 

identified in the 2007 NIOSH evaluation including cleaning the 

ventilation units and repairing the annex flashing and leaking pipes 

in crawl spaces. The visible mold contamination had also been 

cleaned. However, we did find some areas of mold contamination 

on wooden furniture and in the hallways.

Air temperatures were below recommended ANSI/ASHRAE 

comfort guidelines, while RH levels were above ANSI/ASHRAE 

guidelines. Three classrooms had high CO2 concentrations, which 

indicated that not enough outdoor air was being introduced into 

the space. Several of the windows did not close tightly, resulting in 

unconditioned air entering the school. Subsequent discussions with 

the school administration officials revealed that the windows in the 

school were replaced after our site visit.

When the school first reopened in March 2008, employees had 

headaches and nausea. These symptoms resolved after a short time 

and were thought to be related to the odors from the remodeling 

work. The employees reported that the classrooms were cold.

Some employees who had pre-existing allergies moved to other 

schools. The city health department found no differences in the 

frequency or type of visit to the school nurse for the students in the 

time frame of our evaluations.

Keywords: NAICS 611110 (Elementary and Secondary Schools), 

mold, allergies, relative humidity, carbon dioxide, temperature, indoor 

environmental quality, IEQ, ventilation
Page 1 Health Hazard Evaluation Report 2008-0151-3134

Introduction

On March 18, 2008, NIOSH received an HHE request from 

school district management for a middle school in Texas. We had 

conducted an evaluation at this school in September 2007 (HHE 

2007-0380) to look at IEQ issues including mold contamination 

and an incident involving employees inhaling chlorine while 

cleaning the ventilation system vents. The school district 

implemented many of the recommendations we made, and external 

consultants and asked us to conduct a follow-up evaluation at the 

school after it reopened in March 2008. We issued an interim 

letter in June 2008 with preliminary recommendations concerning 

the HVAC systems and windows.

Facility Description

The middle school opened in 1957 as a senior high school. 

The school campus consisted of five buildings: a two-story main 

building that housed the administrative offices, auditorium, band 

rooms, and classrooms; a two-story classroom annex; a physical 

education building containing the school swimming pool; and 

two additional buildings for maintenance and facilities. The main 

building and classroom annex (the buildings of concern) were built 

of concrete block and brick with interior plaster walls. The floors 

were poured concrete on grade or on a pier and post floor support 

system. There was a crawl space for utilities. Most classrooms had 

suspended fiberglass ceiling tiles. The hallways and stairwells had 

no mechanical ventilation and relied on pedestrian traffic for air 

movement. The main hallway of the main building had terrazzo 

flooring, and the rest of the flooring was vinyl or linoleum.

The administrative offices in the main building had a separate 

ducted ventilation system. The classrooms were served by 

individual unit ventilators mounted above the suspended ceiling. 

These units were installed in 2002. They were operated by a 

centralized system using thermostats in each of the classrooms. 

The ventilation units used a closed chilled or heated water system 

from the main utility building. Outdoor air intakes were located in 

external wall openings. The classrooms had functional windows, 

which were closed during our evaluation. The school had been 

closed from September 2007 until March 2008 for repairs and 

remediation. Prior to the school’s reopening, the school district 

worked with an environmental consulting firm to ensure that the 

repairs and remediation had been completed.
Health Hazard Evaluation Report 2008-0151-3134 Page 2

On April 22–24, 2008, we made a site visit that included an 

opening meeting with school district management representatives, 

representatives from the two unions representing teachers and 

staff, the school principal and assistant principal, school nursing 

staff, and representatives from the city health department. The city 

health department conducted a parallel investigation at the request 

of the school district to look at health issues among students.

Following the opening meeting, we walked through the main 

school building and the annex to look for evidence of water 

damage, water incursion, mold, and other potential IEQ 

problems. We collected data and reports from the school district 

management and seven sticky tape surface samples (SKC Inc., 

Eighty Four, Pennsylvania) on furniture and walls of hallways. 

The tape samples were sent to a commercial laboratory for 

mold confirmation and identification using direct microscopic 

techniques with lacto phenol cotton blue stain. We used Q-TrakTM 

Plus Indoor Air Quality Monitors, Model 8554 (TSI Incorporated, 

Shoreview, Minnesota) to measure CO2, CO, temperature, and 

RH throughout the school day in five classrooms, the main office, 

and the library. The Q-TrakTM monitors were precalibrated and 

postcalibrated in our laboratory in Cincinnati, Ohio. A TRAMEX 

Moisture Encounter meter (Tramex Ltd., Littleton, Colorado) 

was used to qualitatively assess the interior wall moisture levels. A 

thermal imaging camera (Fluke FlexCam Ti55FT Thermal Imager, 

Fluke Corporation, Everett, Washington) was used to look at 

temperature differences in the exterior walls.

We interviewed 12 faculty and staff members who had been 

interviewed in 2007 to evaluate their current health concerns and 

occupational history. We also met with city health department staff 

to discuss their investigation of health symptoms and school nurse 

visits.

Assessment
Page 3 Health Hazard Evaluation Report 2008-0151-3134

Results

Building Survey

We found during the walk-though tour that some of the underlying 

moisture issues had been addressed. These included repairing the 

flashing at the back entrance of the annex to fix the ceiling leaks, 

installing a dual pipe system for the ventilation units, draining 

and sealing leaking pipes in the crawl spaces under the buildings, 

regrading the soil around the foundations, and completing the 

cleaning of the ventilation units. The visible mold contamination 

had been cleaned; however, some wooden furniture and cabinets 

and some surfaces in the unconditioned hallways looked like they 

had recurrent mold growth. We collected sticky tape samples in 

these locations (Table 1) and found active mold growth.

Table 1. Microscopic sticky tape sample results

Sample Location Genera Amount of Growth*

Room 113 – Bottom of wooden table Aspergillus/Penicillium group

Aspergillus spp.

Hyaline hyphae

Many conidia/spores

Moderate

Moderate

Room 113 – Corner end table Aspergillus/Penicillium group

Aspergillus spp.

Hyaline hyphae

Hyalodendron spp.

Ascocarps

Alternaria spp.

Many conidia/spores

Many

Many

Moderate hyaline conidia/spores

Few

Rare

Room 301 – Back of desk Aspergillus/Penicillium group

Hyaline hyphae

Aspergillus spp.

Ascopores

Moderate conidia/spores

Moderate

Few

Rare

Hallway of Annex – Under ceiling tile Hyaline hyphae

Aspergillus/Penicillium group

Cladosporium spp.

Dematiaceous hypae

Few

Rare conidia/spores

Rare

Rare

Room 306 – Door of cabinet Aspergillus/Penicillium group

Aspergillus spp.

Cladosporium spp.

Dematiaceous hypae

Hyaline hyphae

Bipolaris/Dreschslera group

Moderate conidia/spores

Moderate

Moderate

Moderate

Moderate

Rare conidia/spores

Room 306 – Desk Cladosporium spp.

Dematiaceous hypae

Many conidia/spores

Many

*Scale: many>moderate>few>rare
Health Hazard Evaluation Report 2008-0151-3134 Page 4

Results

 (continued) We noticed that two ventilation units in the annex and one in the 

library were leaking water from the drainage traps; we reported 

them to the project manager who took steps to address the leaks. 

We also observed that the windows did not close tightly, and 

caulk was missing in several areas, allowing unconditioned humid 

outdoor air into the buildings. Figure 1 is a thermal image showing 

the leakage of warm air into the classroom. A gap was also visible 

between the edge of the window and the frame.

Figure 1. Thermal image of window in Room 305 shows outdoor air 

entering the room at a higher temperature than inside.

IEQ measurements (CO2, CO, temperature, and RH) made during 

the site visit are summarized in Table 2. Graphs of the data for 

each room are in Appendix A. A spot check of outdoor conditions 

showed a CO2 concentration of 405 ppm, a temperature of 87°F, 

and a RH level of 63%. Rooms 108, 203, and 212 had CO2 levels 

above the recommended ANSI/ASHRAE guidelines [ANSI/

ASHRAE 2010a]. CO2, a normal constituent of exhaled breath, 

is not considered a building air pollutant. However, if CO2

concentrations are elevated, the amount of outdoor air introduced 

into the ventilated space may need to be increased to dilute typical 

building contaminants. Rooms 111 and 213, which had the lowest 

CO2 concentrations, were not occupied when the monitoring was 

done. The main office was on a central ventilation system and was 

operating within the ANSI/ASHRAE guidelines. CO levels were 

low, ranging from nondetected to 1.6 ppm. The presence of CO 

in the building may have come from vehicular traffic around the 

building. Additional information on IEQ including the ANSI/

ASHRAE guidelines can be found in Appendix B.
Page 5 Health Hazard Evaluation Report 2008-0151-3134

Results

 (continued) In Rooms 108, 111, 203, 212, 213, and the library, the temperatures 

and RH levels were outside comfort guidelines (Table 2). The 

ANSI/ASHRAE Standard 55-2010: Thermal Environmental 

Conditions for Human Occupancy, specifies conditions in which 

80% or more of the occupants would be expected to find the 

environment thermally acceptable [ANSI/ASHRAE 2010b]. These 

guidelines have been established for comfort levels that can affect 

productivity, not on the basis of health effects. The current ANSI/

ASHRAE guidelines also recommend maintaining RH at or below 

65% [ANSI/ASHRAE 2010a]. Excessive humidity can promote the 

growth of microorganisms and dust mites. The moisture readings 

in Room 108, the teachers’ lounge, and Room 410 showed no 

evidence of excess moisture on wall surfaces.

Table 2. Indoor environmental quality measurements made on April 23, 2008, at the middle school

Location Sampling Time

(minutes)

CO2 Range 

(ppm)

Temperature 

Range (°F)

RH Range (%)

Library (occupied) 474 402–571 64–70 60–73

Main Office (occupied) 505 657–1097 69–73 51–69

Room 108 – Classroom 

 (occupied)

399 492–1288 65–69 64–75

Room 111 – Cooking

 Lab (unoccupied)

481 395–601 67–69 59–75

Room 203 – Classroom 474 541–1153 66–69 62–83

Room 212 – Classroom

 (occupied)

475 735–2316 63–68 66–74

Room 213 – Classroom

 unoccupied 

477 440–797 64–69 65–87

Review of Consultant Report

School management hired an environmental consultant to conduct 

an in-depth IEQ assessment. That evaluation was conducted on 

March 3–25, 2008. The consultant conducted a visual assessment 

of all school buildings; evaluated the ventilation systems; checked 

building pressurization; measured CO2, CO, temperature, and RH; 

evaluated total VOCs during the remodeling process; and collected 

area air samples for mold. They identified problems with the 

ventilation systems that were addressed before the school reopened in 

March 2008. They also found fluctuations in RH levels and building 
Health Hazard Evaluation Report 2008-0151-3134 Page 6

pressurization believed to come from leakage around the windows. 

The consultant found that low levels of total VOCs (1 ppm) were 

present from the remodeling work and that the levels were decreasing 

as the work was completed. The mold sampling showed that 

concentrations were lower in the school buildings when compared to 

the outdoor concentrations and that the types of mold in both the 

indoor and outdoor samples were similar.

Employee Interviews

Seven of the 12 employees we interviewed attributed the headache and 

nausea symptoms that occurred soon after the school was reopened in 

part to odors from the recent repainting, floor stripping and waxing, 

and carpet installation. Staff complaints about odors and symptoms 

to school management reportedly decreased over time after the school 

was reopened, remodeling was completed, and odors dissipated.

Several employees who reported upper respiratory, sinus, and eye 

irritation during our September 2007 evaluation were interviewed 

again in April 2008. Most employees we interviewed who were 

symptomatic in September 2007 reported that their symptoms 

improved during the time classes were held at a different middle 

school, with recurrence of symptoms upon return to this school in 

March 2008. Most reported these symptoms improved with medical 

treatment; seven teachers were reassigned to other schools at their 

request and/or based on physician recommendations. Most staff we 

interviewed reported concerns about temperature fluctuations in 

the classrooms, with most stating the rooms were too cold and were 

uncomfortable for staff and students.

Health Department Investigation 

At the request of the school district, staff from the city health 

department investigated health symptom incidence/school nurse visits 

among students in the 3 years prior to our 2008 site visit (excluding 

the approximately 6 months from September 2007 to March 2008 

when students were relocated to another school). According to their 

records review, approximately 50% of visits to the school nurse were 

a result of injuries, and approximately 50% were due to symptoms 

such as nausea, stomachache, headache, and dizziness. Only a few 

respiratory complaints occurred over the 3-year period. Of note, the 

number of school nurse visits by students was similar in each year of 

the 3-year period.

Results

 (continued)
Page 7 Health Hazard Evaluation Report 2008-0151-3134

2010 Follow-up

In March 2010 we spoke with administrative staff at the middle school 

to learn whether the classroom windows throughout the buildings 

had been replaced, as discussed at our April 2008 closing meeting. 

Additionally, we inquired about reports of health concerns among 

staff in the year following our second evaluation. We learned that all 

windows in the facility were replaced in 2008, and the annex building 

had reopened with no apparent health concerns among staff. Some 

teachers who previously reported symptoms chose to teach in portable 

trailers on the middle school campus instead of returning to the 

regular classrooms.

Results

 (continued)

Discussion

Overall, we found that the mold contamination issues at the school 

had improved since our 2007 evaluation, although the ventilation 

units were not reducing RH to the recommended levels. These 

individual ventilation units were designed to have continuous 

temperature control but rely on the dehumidification of the 

cooling system to remove excess humidity from the air. This design 

is known to have problems maintaining humidity within suggested 

comfort guidelines in a moderate or hot, humid environment 

[ASHRAE 2006]. In a humid climate, Lstiburek recommends that 

the temperature of the outdoor air introduced into the building 

be lowered to 55°F to dehumidify the air [Lstiburek 1993]. This 

air is too cold to deliver directly to the classroom without some 

additional reheat mechanism. The windows were also in disrepair, 

which likely allowed unconditioned humid air to enter. Since our 

evaluation, the windows in the school have been replaced. During 

our evaluation we saw evidence that mold was starting to grow 

again on some wooden furniture and in unconditioned hallways, 

likely due to the high RH levels in these areas. Mold spores need 

water, food, and an acceptable temperature to grow. Because mold 

spores are always present in the environment, the easiest of these 

factors to control indoors is the water (i.e., RH). 

The ventilation units were clean; two units had water leakage 

from the drain lines, which was fixed during our visit. The CO2

levels in Rooms 108, 203, and 212 exceeded the ANSI/ASHRAE 

recommended guidelines, which can indicate insufficient 

quantities of outdoor air being introduced into the space. 

However, adding additional untreated outdoor air can compound 

the high RH problem. The ventilation units were set to low 
Health Hazard Evaluation Report 2008-0151-3134 Page 8

Discussion

 (continued) temperatures to reduce the RH levels that resulted in comfort 

issues for the staff. Maintaining comfort parameters (temperature, 

RH) at recommended levels has been shown to help resolve or 

improve symptoms among building occupants.

Employee reports of headache and nausea when the school 

was first reoccupied have resolved with time. These symptoms 

were likely due to the odors and chemicals from the remodeling 

activities that were finished just prior to the school reopening. 

Several of the employees with symptoms in September 2007 

had been reassigned to other schools. Individuals who reported 

upper respiratory, sinus, and eye irritation in September 2007 

felt better when they moved to another school and reported that 

symptoms returned when they moved back to this school. Most 

of the employees stated that the symptoms responded to medical 

treatment. The city health department study found no changes in 

the student health reports during this time period.

Conclusions

We found that the school district had implemented many of the 

recommendations for the middle school, including regrading 

soil around the building, repairing pipes in the crawl spaces, and 

remediating mold. However, work on the ventilation systems was 

still needed to address cold temperatures, high RH levels, and 

insufficient outdoor air.

Recommendations

The following recommendations were based on our survey 

observations, sampling results, and interviews.

1. Consult with a qualified ventilation engineer to provide 

conditioned 55°F outdoor air (to remove excess RH) to the 

individual ventilation units. To conserve energy and heat 

the cold dehumidified outdoor air, air could be recirculated 

from the classroom through the ventilation system or a 

heat exchanger. The amount of untreated air entering 

the classrooms from the hallways should be controlled. 

Ventilation units in the school should be set to provide 10 

CFM of outdoor air per person for classrooms as specified 

under the Texas Voluntary Indoor Air Quality Guidelines 

for Government Buildings at http://www.dshs.state.tx.us/

iaq/SchoolsGuide.shtm#HVAC_sys. The temperature 
Page 9 Health Hazard Evaluation Report 2008-0151-3134

Recommendations

 (continued) and RH should follow current ANSI/ASHRAE comfort 

guidelines. Because the air in hallways is untreated, the 

walls between the hallways and classrooms should be treated 

similarly to exterior walls. This treatment includes limiting 

the opportunity for air to migrate from the hallways to the 

classrooms and installing a vapor barrier on the hallway side 

of the wall.

2. Continue clean-up of the residual mold contamination 

using appropriate techniques as outlined in the U.S. 

EPA document “Mold Remediation in Schools and 

Commercial Buildings” at http://www.epa.gov/mold/pdfs/

moldremediation.pdf and the Texas Department of State 

Health Services mold program at http://www.dshs.state.

tx.us/mold/default.shtm.

3. Inform building occupants of the actions taken to address 

IEQ problems and the rationale for decisions made to 

address these problems.

4. Start an IEQ management program to address the 

IEQ issues that have evolved over the past several years 

and prevent them from recurring. An IEQ manager or 

administrator with clearly defined responsibilities, authority, 

and resources should be selected. This individual should 

have a good understanding of the buildings’ structure and 

function, and should be able to effectively communicate 

with occupants. Although no comprehensive regulatory 

standards specific to IEQ have been established, guidelines 

have been developed by organizations such as ASHRAE, 

NIOSH, and the U.S. EPA. An employee representative 

should assist with communication and should be included 

in the IEQ management program. The NIOSH/U.S. 

EPA document, “Building Air Quality: A Guide for 

Building Owners and Facility Managers” may be helpful. 

A companion NIOSH/U.S. EPA guide, “Building Air 

Quality Action Plan,” can serve as a checklist for developing 

and assessing an IEQ management program. Additional 

information specifically for IEQ in schools is available on 

the U.S EPA website at http://www.epa.gov/iaq/schools/

index.html.

5. Encourage employees with potential work-related health 

concerns to seek evaluation and care from a healthcare 

provider who is knowledgeable in occupational medicine 

and IEQ issues.
Health Hazard Evaluation Report 2008-0151-3134 Page 10

References

ANSI/ASHRAE [2010a]. Ventilation for acceptable indoor air 

quality. American National Standards Institute/ASHRAE standard 

62.1-2010. Atlanta, GA: American National Standards Institute/

American Society of Heating, Refrigerating, and Air-Conditioning 

Engineers, Inc.

ANSI/ASHRAE [2010b]. Thermal environmental conditions 

for human occupancy. American National Standards Institute/

ASHRAE standard 55-2010. Atlanta, GA: American National 

Standards Institute/American Society for Heating, Refrigerating, 

and Air-Conditioning Engineers, Inc.

ASHRAE [2006]. Humidity control and design guide for 

commercial and institutional buildings. Atlanta, GA: American 

Society for Heating, Refrigerating, and Air-Conditioning 

Engineers, Inc.

Lstiburek J [1993]. Humidity control in the humid south. Building 

Science Research Report 9302. [http://www.buildingscience.com/

documents/reports/rr-9302-humidity-control-in-the-humid-south] 

Date accessed: June 2011.
Page 11 Health Hazard Evaluation Report 2008-0151-3134

Appendix A: Indoor Environmental Quality Graphs

Figure A1. Graph of CO2, CO, temperature, and RH for the library.

Figure A2. Graph of CO2, temperature, and RH for the main office.*

*meter had no CO monitoring capability
Health Hazard Evaluation Report 2008-0151-3134 Page 12

Appendix A: Indoor Environmental Quality Graphs

 (continued)

Figure A3. Graph of CO2, CO, temperature, and RH for Room 108.

Figure A4. Graph of CO2, CO, temperature, and RH for Room 111.
Page 13 Health Hazard Evaluation Report 2008-0151-3134 

Appendix A: Indoor Environmental Quality Graphs

 (continued)

Figure A5. Graph of CO2, CO, temperature, and RH for Room 203.

Figure A6. Graph of CO2, CO, temperature, and RH for Room 212.
Health Hazard Evaluation Report 2008-0151-3134 Page 14

Appendix A: Indoor Environmental Quality Graphs

 (continued)

Figure A7. Graph of CO2, CO, temperature, and RH for Room 213.
Page 15 Health Hazard Evaluation Report 2008-0151-3134

Appendix B: Occupational Exposure Limits and Health Effects

Microbial Contamination

Exposure to microbes is not unique to the indoor environment. No environment, indoors or out, is 

completely free from microbes, even a surgical operating room. Remediation of microbial contamination 

may improve IEQ conditions even though a specific cause-effect relationship is not determined. NIOSH 

investigators routinely recommend the remediation of observed microbial contamination and the 

correction of situations that are favorable for microbial growth and bioaerosol dissemination.

Mold

The types and severity of symptoms related to exposure to mold in the indoor environment depend in 

part on the extent of the mold present, the extent of the individual’s exposure, and the susceptibility 

of the individual (for example, whether they have pre-existing allergies or asthma). In general, excessive 

exposure to fungi may produce health problems by several primary mechanisms, including allergy or 

hypersensitivity, infection, and toxic effects. Additionally, molds produce a variety of VOCs, the most 

common of which is ethanol, that have been postulated to cause upper airway irritation. However, as 

discussed above, potential irritant effects of VOCs from exposure to mold in the indoor environment are 

not well understood. Evidence also shows that exposure to fungal fragments that can contain allergens, 

toxins, and (1→3)-β-D-glucan may occur [Górney et al. 2002; Brasel et al. 2005; Reponen et al. 2006].

Allergic responses are the most common type of health problem associated with exposure to molds. These 

health problems may include sneezing; itching of the nose, eyes, mouth, or throat; nasal stuffiness and 

runny nose; and red, itchy eyes. Repeated or single exposure to mold or mold spores may cause previously 

nonsensitized individuals to become sensitized. Molds can trigger asthma symptoms (shortness of breath, 

wheezing, cough) in persons who are allergic to mold. In the 2004 report, “Damp Indoor Spaces and Health,” 

the IOM found sufficient evidence of an association between mold or dampness indoors and nasal and throat 

symptoms, asthma symptoms in sensitized asthmatics, wheeze, cough, and hypersensitivity pneumonitis in 

susceptible persons [IOM 2004]. The IOM found limited or suggestive evidence of an association between 

lower respiratory illness in healthy children and damp indoor spaces. There was inadequate or insufficient 

evidence to determine whether an association exists between dyspnea, airflow obstruction in healthy persons, 

mucous membrane irritation, skin symptoms, chronic obstructive pulmonary disease, asthma development, 

inhalation fevers in nonoccupational settings, fatigue, cancer, reproductive effects, neuropsychiatric effects, 

lower respiratory illness in healthy adults, gastrointestinal problems, rheumatologic or immune problems, 

or acute idiopathic pulmonary hemorrhage in infants. No health conditions met the level of evidence for 

causation. In 2009, WHO published guidelines for protection of public health from mold and other exposures 

in damp buildings [WHO 2009]. Based on its review of the scientific literature for this report, the WHO 

concluded that there was sufficient epidemiologic evidence that occupants of damp buildings are at risk of 

developing upper and lower respiratory tract symptoms (including cough, wheeze, and dyspnea), respiratory 

infections, asthma, and exacerbation of asthma. The WHO also concluded that limited evidence suggests an 

association between bronchitis and allergic rhinitis and damp buildings. They noted clinical evidence that 

exposure to mold and other microbial agents in damp buildings is associated with hypersensitivity pneumonitis.
Health Hazard Evaluation Report 2008-0151-3134 Page 16

People with weakened immune systems (immune-compromised or immune-suppressed individuals) may 

be more vulnerable to infections by molds. For example, Aspergillus fumigatus is a fungal species that 

has been found almost everywhere on every conceivable type of substrate. It has been known to infect the 

lungs of immune-compromised individuals who inhale the airborne spores [Wald and Stave 1994; Brandt 

et al. 2006]. Healthy individuals are usually not vulnerable to infections from airborne mold exposure.

No exposure guidelines for mold in air exist, so it is not possible to distinguish between “safe” and 

“unsafe” levels of exposure. Nevertheless, the potential for health problems is an important reason to 

prevent indoor mold growth and to remediate any indoor mold contamination. Moisture intrusion, 

along with nutrient sources such as building materials or furnishings, allows mold to grow indoors, so 

it is important to keep the building interior and furnishings dry. NIOSH concurs with the U.S. EPA’s 

recommendations to remedy mold contamination in indoor environments at http://www.epa.gov/iaq/

molds/mold_remediation.html [U.S. EPA 2001; Redd SC 2002]. Additional information on health effects 

and mold remediation can be found in the CDC document “Mold Prevention Strategies and Possible 

Health Effects in the Aftermath of Hurricanes and Major Floods” at http://www.cdc.gov/mmwr/preview/

mmwrhtml/rr5508a1.htm.

No standards specific to the nonindustrial indoor environment exist. Measurement of indoor 

environmental contaminants has seldom proved helpful in determining the cause of symptoms except 

where there are unusual sources or a proven relationship between specific exposures and disease. With few 

exceptions, concentrations of frequently measured chemical substances in the indoor work environment 

fall well below the recommended OELs published by NIOSH [NIOSH 2005], ACGIH [ACGIH 2011], 

and AIHA [AIHA 2010], and the mandatory PELs set by OSHA [29 CFR 1910 (general industry)]. ANSI/

ASHRAE has published recommended building ventilation and thermal comfort guidelines [ANSI/

ASHRAE 2010a; ANSI/ASHRAE 2010b]. The ACGIH and AIHA have also developed a manual of 

guidelines for approaching investigations of building-related symptoms that might be caused by airborne 

living organisms or their effluents [ACGIH 1999; AIHA 2008]. Other resources that provide guidance for 

establishing acceptable IEQ are available through U.S. EPA at http://www.epa.gov/iaq/, especially the 

U.S. EPA Indoor Air Quality Tools for Schools at http://www.epa.gov/iaq/schools/ and the joint U.S. 

EPA/NIOSH document, Building Air Quality, A Guide for Building Owners and Facility Managers at 

http://www.epa.gov/iaq/largebldgs/baqtoc.html.

Heating, Ventilating, and Air-Conditioning

One of the most common deficiencies in the indoor environment is the improper operation and 

maintenance of ventilation systems and other building components [Rosenstock 1996]. We have found 

that correcting HVAC problems often reduces reported symptoms. Most studies of ventilation rates and 

building occupant symptoms have shown that rates below 10 Ls-1

/person (which equates to 20 CFM 

per person) are associated with one or more health symptoms [Seppanen et al 1999]. Moreover, higher 

ventilation rates, from 10 Ls-1

/person up to 20 Ls-1/person, have been associated with further significant 

decreases in the prevalence of symptoms [Seppanen et al. 1999]. Thus, improved HVAC operation and 

Appendix B: Occupational Exposure Limits and Health Effects

 (continued)
Page 17 Health Hazard Evaluation Report 2008-0151-3134

maintenance, higher ventilation rates, and comfortable temperature and RH can all potentially serve to 

improve symptoms without ever identifying any specific cause-effect relationships. When conducting an 

IEQ evaluation, we often measure ventilation and comfort indicators, such as CO2

, temperature, and RH 

to provide information relative to the functioning and control of HVAC systems.

Carbon Dioxide

CO2 is a normal constituent of exhaled breath and is not considered a building air pollutant. It can be 

used as an indicator of whether sufficient quantities of outdoor air are being introduced into an occupied 

space for acceptable odor control. However, CO2

 is not an effective indicator of ventilation adequacy if 

the ventilated area is not occupied at its usual occupant density at the time the CO2

 is measured. ANSI/

ASHRAE notes in an informative appendix to standard 62.1 that indoor CO2

 concentrations no greater 

than about 700 ppm above outdoor CO2

 concentrations will satisfy a substantial majority (about 80%) 

of visitors with regard to odor from sedentary building occupants (body odor) [ANSI/ASHRAE 2010a]. 

Elevated CO2

 concentrations suggest that other indoor contaminants may also be increased. If CO2

concentrations are elevated, the amount of outdoor air introduced into the ventilated space may need to 

be increased. When CO2

 concentrations are used as an indicator to determine outdoor air requirements, 

ventilation system designs that rely on duct-mounted CO2

 sensors should have some form of ventilation 

efficiency documentation that relates concentration values observed at the duct location with those 

observed within the breathing zone of the occupied space.

Temperature and Relative Humidity

Temperature and RH measurements are often collected as part of an IEQ evaluation because these 

parameters affect the perception of comfort in an indoor environment. The perception of thermal comfort 

is related to one’s metabolic heat production, the transfer of heat to the environment, physiological 

adjustments, and body temperature [NIOSH 1986]. Heat transfer from the body to the environment is 

influenced by factors such as temperature, humidity, air movement, personal activities, and clothing. 

The ANSI/ASHRAE Standard 55-2010: Thermal Environmental Conditions for Human Occupancy, 

specifies conditions in which 80% or more of the occupants would be expected to find the environment 

thermally acceptable [ANSI/ASHRAE 2010b]. Assuming slow air movement and 50% RH, the operative 

temperatures recommended by ANSI/ASHRAE range from 68.5°F to 76°F in the winter, and from 75°F 

to 80.5°F in the summer. The difference between the two is largely due to seasonal clothing selection. 

ANSI/ASHRAE also recommends that RH be maintained at or below 65% [ANSI/ASHRAE 2010a]. 

Excessive humidity can promote the excessive growth of microorganisms and dust mites.

References

ACGIH [1999]. Bioaerosols: assessment and control. Cincinnati, OH: American Conference of 

Governmental Industrial Hygienists.

Appendix B: Occupational Exposure Limits and Health Effects

 (continued)
Health Hazard Evaluation Report 2008-0151-3134 Page 18

ACGIH [2011]. 2010 TLVs® and BEIs®: threshold limit values for chemical substances and physical 

agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental 

Industrial Hygienists.

AIHA [2008]. Recognition, evaluation, and control of indoor mold. Prezant B, Weekes DM, Miller JD, 

eds. Fairfax, VA: American Industrial Hygiene Association.

AIHA [2010]. AIHA 2010 Emergency response planning guidelines (ERPG) & workplace environmental 

exposure levels (WEEL) handbook. Fairfax, VA: American Industrial Hygiene Association.

ANSI/ASHRAE [2010a]. Ventilation for acceptable indoor air quality. American National Standards 

Institute/ASHRAE standard 62.1-2010. Atlanta, GA: American National Standards Institute/American 

Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc.

ANSI/ASHRAE [2010b]. Thermal environmental conditions for human occupancy. American National 

Standards Institute/ASHRAE standard 55-2010. Atlanta, GA: American National Standards Institute/

American Society for Heating, Refrigerating, and Air-Conditioning Engineers, Inc.

Brandt M, Brown C, Burkhart J, Burton N, Cox-Ganser J, Damon S, Falk H, Fridkin S, Garbe P, 

McGeehin M, Morgan J, Page E, Rao C, Redd S, Sinks T, Trout D, Wallingford K, Warnock D, Weissman 

D [2006]. Mold prevention strategies and possible health effects in the aftermath of hurricanes and major 

floods. MMWR 55(RR-8):1–27.

Brasel TL, Martin JM, Carriker CG, Wilson SC, Straus DC [2005]. Detection of airborne Stachybotrys

chartarum macrocyclic trichothecene mycotoxins in the indoor environment. Appl Environ Microbiol 

71(11):7376–7388.

CFR. Code of Federal Regulations. Washington, DC: U.S. Government Printing Office, Office of the 

Federal Register.

Górny RL, Reponen T, Willeke K, Schmechel D, Robine E, Boissier M, Grinshpun SA [2002]. Fungal 

fragments as indoor air biocontaminants. Appl Environ Microbiol 68(7):3522–3531.

IOM [2004]. Human health effects associated with damp indoor environments. In: Damp indoor spaces 

and health. Washington, DC: Institute of Medicine, National Academy Press, pp. 183–269.

NIOSH [1986]. Criteria for a recommended standard: occupational exposure to hot environments, revised 

criteria. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control, 

National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 86–13.

Appendix B: Occupational Exposure Limits and Health Effects

 (continued)
Page 19 Health Hazard Evaluation Report 2008-0151-3134

NIOSH [2005]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational 

Safety and Health, DHHS (NIOSH) Publication No. 2005–149. [http://www.cdc.gov/niosh/npg/]. Date 

accessed: June 2011.

Redd SC [2002]. State of the science on molds and human health. Statement for the Record Before the 

Subcommittee on Oversight and Investigations and Housing and Community Opportunity, Committee 

on Financial Services, United States House of Representatives. Atlanta, GA: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention.

Reponen T, Seo S-C, Iossifova Y, Adhikari A, Grinshpun SA [2006]. New field-compatible method for 

collection and analysis of β-glucan in fungal fragments. Abstracts of the International Aerosol Conference, 

St. Paul, Minnesota, p. 955.

Rosenstock L [1996]. NIOSH Testimony to the U.S. Department of Labor on indoor air quality. Applied 

Occupational and Environmental Hygiene 11(12):1365–1370.

Seppanen OA, Fisk WJ, Mendell MJ [1999]. Association of ventilation rates and CO2 concentrations with 

health and other responses in commercial and institutional buildings. Indoor Air 9(4):226–252.

U.S. EPA [2001]. Mold remediation in schools and commercial buildings. Washington, DC: United States 

Environmental Protection Agency, Office of Air and Radiation, Indoor Environments Division. EPA 

Publication No. 402–K–01–001.

Wald P, Stave G [1994]. Fungi. In: Physical and biological hazards of the workplace. New York: Van 

Nostrand Reinhold, p. 394.

WHO [2009]. WHO guidelines for indoor air quality: dampness and mould. Geneva, Switzerland: World 

Health Organization. [http://www.euro.who.int/__data/assets/pdf_file/0017/43325/E92645.pdf]. Date 

accessed: June 2011.

Appendix B: Occupational Exposure Limits and Health Effects

 (continued)
Health Hazard Evaluation Report 2008-0151-3134 Page 20

Acknowledgments and

Availability of Report

The Hazard Evaluations and Technical Assistance Branch 

(HETAB) of the National Institute for Occupational Safety and 

Health (NIOSH) conducts field investigations of possible health 

hazards in the workplace. These investigations are conducted 

under the authority of Section 20(a)(6) of the Occupational Safety 

and Health Act of 1970, 29 U.S.C. 669(a)(6) which authorizes 

the Secretary of Health and Human Services, following a written 

request from any employer or authorized representative of 

employees, to determine whether any substance normally found 

in the place of employment has potentially toxic effects in such 

concentrations as used or found. HETAB also provides, upon 

request, technical and consultative assistance to federal, state, and 

local agencies; labor; industry; and other groups or individuals to 

control occupational health hazards and to prevent related trauma 

and disease.

The findings and conclusions in this report are those of the 

authors and do not necessarily represent the views of NIOSH. 

Mention of any company or product does not constitute 

endorsement by NIOSH. In addition, citations to websites 

external to NIOSH do no constitute NIOSH endorsement of 

the sponsoring organizations or their programs or products. 

Furthermore, NIOSH is not responsible for the content of these 

websites. All Web addresses referenced in this document were 

accessible as of the publication date.

This report was prepared by Nancy Clark Burton and John Gibbins 

of HETAB, Division of Surveillance, Hazard Evaluations and Field 

Studies. Ventilation consultation was provided by Kenneth Mead, 

Division of Applied Research and Technology. Analytical support 

was provided by Microbiology Specialists Incorporated, Houston, 

Texas. Health communication assistance was provided by Stefanie 

Evans. Editorial assistance was provided by Ellen Galloway. 

Desktop publishing was performed by Greg Hartle.

Copies of this report have been sent to employee and management 

representatives at the middle school, the state health department, 

and the Occupational Safety and Health Administration 

Regional Office. This report is not copyrighted and may be freely 

reproduced. The report may be viewed and printed at http://www.

cdc.gov/niosh/hhe/. Copies may be purchased from the National 

Technical Information Service (NTIS) at 5825 Port Royal Road, 

Springfield, Virginia 22161.
Below is a recommended citation for this report:

NIOSH [2011]. Health hazard evaluation report: assessment of mold and indoor 

environmental quality in a middle school – Texas. By Burton NC, Gibbins J. 

Cincinnati, OH: U.S. Department of Health and Human Services, Centers for 

Disease Control and Prevention, National Institute for Occupational Safety and 

Health, NIOSH HETA No. 2008-0151-3134.

To receive NIOSH documents or information about 

occupational safety and health topics, contact NIOSH at:

1-800-CDC-INFO (1-800-232-4636)

TTY: 1-888-232-6348

E-mail: cdcinfo@cdc.gov

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NIOSH eNews by visiting www.cdc.gov/niosh/eNews.

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