Health Hazard Evaluation Report 2013-0145-3209 Page 1

Evaluation of Environmental Controls 

at a Homeless Shelter Associated with a 

Tuberculosis Outbreak – Texas 

Report No. 2013-0145-3209

May 2014

Stephen B. Martin, Jr., MS, PE

R. Brent Lawrence, MS, GSP

Kenneth R. Mead, PhD, PE

U.S. Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
Page 2 Health Hazard Evaluation Report 2013-0145-3209

Contents

Highlights .......................................................................................... i

Abbreviations.................................................................................. iv

Summary........................................................................................... 1

Introduction ..................................................................................... 2

Background ..................................................................................... 3

Assessment....................................................................................... 4

Results & Discussion ....................................................................... 5

Conclusions ....................................................................................20

Recommendations ........................................................................21

Outline of Future NIOSH Involvement...................................... 25

References.......................................................................................27

Tables...............................................................................................30

Figures .............................................................................................39

Acknowledgements ......................................................................42

The employer is required to post a copy of this report for 30 days at or near the 

workplace(s) of affected employees. The employer must take steps to ensure 

that the posted report is not altered, defaced, or covered by other material.

The cover photo is a close-up image of sorbent tubes, which are used by the HHE

Program to measure airborne exposures. This photo is an artistic representation that may

not be related to this Health Hazard Evaluation.
Health Hazard Evaluation Report 2013-0145-3209 Page i

Highlights of this Evaluation

The National Institute for Occupational Safety and Health (NIOSH) received a technical 

assistance request from the manager of a large homeless shelter in Dallas, Texas. The 

request asked NIOSH to assess the heating, ventilation, and air-conditioning systems and 

make recommendations to improve overall environmental controls, as the shelter had 

epidemiological links to an ongoing tuberculosis (TB) outbreak.

What NIOSH Did

● Visited the shelter on June 5-7, 2013.

● Met with representatives from the Dallas County Department of Health and Human 

Services to discuss the ongoing TB outbreak, and to outline our goals and objectives for 

our site visits.

● Recorded the physical sizes of occupied spaces.

● Measured ventilation air flow into/from occupied spaces.

● Collected information on all air-handling units.

What NIOSH Found

● The shelter was working closely with the Dallas County Department of Health and 

Human Services on TB outbreak response efforts, including implementation of more 

robust administrative controls. 

● Air-handling units were well maintained, fitted with proper filter configurations, and in 

good working order.

● Little outdoor air was being supplied to occupied spaces by building mechanical systems 

under certain occupancy and environmental conditions.

● There was no clearly defined area to separate guests suspected of having tuberculosis or 

other airborne infectious disease from the general guest population.

● Some medical clinic examination rooms and most bathrooms and shower rooms at the 

facility were incorrectly operating under positive pressure compared to adjacent spaces.

● A written respiratory protection plan did not exist.

What the Shelter Can Do

● Continue to work in close conjunction with the Dallas County Department of Health 

and Human Services to improve overall administrative controls to help ensure rapid 

identification of guests suspected to have tuberculosis.

● Develop a comprehensive infection control plan with input from the Dallas County 

Department of Health and Human Services.
Page ii Health Hazard Evaluation Report 2013-0145-3209

● Modify the sequence of operations for existing air-handling units and/or augment 

shelter ventilation systems to provide adequate outdoor air to all occupied spaces under 

all occupancy and environmental conditions.

● For each air-handling unit, install the highest efficiency air filter possible that is 

consistent with the proper operation of the air-handling unit.

● Create an enclosed, ventilated space in the pavilion sleeping area for use as a respiratory 

separation area, when necessary.

● Adjust or modify ventilation systems to properly maintain all medical examination 

rooms under negative pressure relative to the adjacent spaces.

● Install a properly designed upper-air ultraviolet germicidal irradiation system in the 

pavilion sleeping area.

● Repair or replace bathroom and shower room exhaust fans so those spaces are 

maintained under negative pressure relative to adjacent spaces. 

● Develop and implement a written respiratory protection program that meets the 

requirements of the Occupational Safety and Health Administration’s respiratory 

protection standard 29 Code of Federal Regulations 1910.134.

● Develop and implement a written operation and maintenance plan for shelter heating, 

ventilation, and air-conditioning systems, to include a filter replacement schedule.
Health Hazard Evaluation Report 2013-0145-3209 Page iii

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Page iv Health Hazard Evaluation Report 2013-0145-3209

Abbreviations

μm Micrometer

AHU(s) Air-handling unit(s)

ACGIH American Conference of Governmental Industrial Hygienists

ACH Air changes per hour

AII Airborne infection isolation

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

DCHHS Dallas County Department of Health and Human Services

DRDS Division of Respiratory Disease Studies

DTBE Division of Tuberculosis Elimination

FGI Facility Guidelines Institute

HEPA High-efficiency particulate air

HVAC Heating, ventilation, and air-conditioning

ICP Infection control plan

μW/cm2 Microwatts per square centimeter

mJ/cm2 Millijoules per square centimeter

MERV Minimum efficiency reporting value

nm Nanometer

NCHHSTP National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention

NIOSH National Institute for Occupational Safety and Health

O&M Operation and maintenance

OSHA Occupational Safety and Health Administration

REL Recommended Exposure Limit

RH Relative humidity

TB Tuberculosis

UV Ultraviolet

UVGI Ultraviolet germicidal irradiation 
Health Hazard Evaluation Report 2013-0145-3209 Page 1

Summary

On May 22, 2013, the National Institute for Occupational Safety and Health (NIOSH) 

received a request for technical assistance from the shelter manager at a large homeless 

shelter in Dallas, Texas, linked to an ongoing tuberculosis outbreak. The request asked 

NIOSH to assess the heating, ventilation, and air-conditioning (HVAC) systems and make 

recommendations to improve overall environmental controls at the shelter.

During an on-site evaluation of the 

homeless shelter in June 2013, we collected 

physical and ventilation measurements 

in all key areas of the facility. We focused 

on areas where shelter guests typically 

congregate or spend significant amounts 

of time. We recorded the make and model 

number of all air-handling units (AHUs) 

providing air to the facility, and visually 

inspected the units. When possible, we 

measured the air flow rate through supply 

diffusers and return grilles. 

The AHUs in place were state-of-the-art 

and were controlled by a modern building 

automation system. The ventilation systems 

were well maintained and functional during 

our visit, and all AHUs were equipped 

with proper filter configurations. Despite 

their excellent condition and maintenance, 

certain aspects of the ventilation systems’ 

operation could potentially contribute to 

airborne disease transmission among shelter guests. During our visit, it appeared the AHUs 

were not providing adequate outdoor air to the occupied spaces under certain occupancy 

and environmental conditions, as is required by the Dallas Mechanical Code and ASHRAE 

standards. In addition to alleviating odors and maintaining occupant comfort, outdoor air 

serves to dilute infectious aerosols, such as Mycobacterium tuberculosis droplet nuclei that are 

responsible for TB transmission.

Since the TB outbreak began, the shelter has taken numerous steps to improve administrative 

controls, particularly when it comes to identifying guests showing signs and symptoms of TB. 

We recommend additional improvements to the administrative and environmental controls 

at the shelter. From a ventilation standpoint, we suggest that all occupied spaces at the shelter 

complex be supplied adequate amounts of outdoor air, as prescribed by the Dallas Mechanical 

Code and ASHRAE standards. In addition, we identified an area that should be converted 

for respiratory separation purposes. This space could serve to separate a guest suspected 

of having TB or other respiratory diseases from the remainder of the guest population, 

NIOSH investigators 

conducted an assessment 

of environmental controls 

at a large Dallas, Texas, 

homeless shelter linked to an 

ongoing tuberculosis outbreak. 

The investigation revealed 

problems with the existing 

environmental controls, along 

with needed improvements 

in administrative controls and 

respiratory protection. Detailed 

recommendations are provided 

in this report to improve the 

shelter environment and 

reduce the likelihood of 

disease transmission.
Page 2 Health Hazard Evaluation Report 2013-0145-3209

until medical evaluation, transport or treatment could be obtained. We also recommend 

developing a written infection control plan, an HVAC operation and maintenance plan, and 

a written respiratory protection program. Having these plans/programs in place will help 

the shelter under normal operating conditions, and especially during future outbreaks of 

respiratory disease.

Introduction

Since the middle of 2009, Dallas County (TX) has experienced an increase in the number 

of epidemiologically-linked cases of tuberculosis (TB). Molecular analyses conducted by 

the CDC identified two separate clusters of TB in the community, and both clusters are 

disproportionately affecting the Dallas-area homeless community. Since September 2009, 58 

TB cases belonging to the G10508 genotype cluster have been identified. Of those 58 cases, 43 

(74%) had a recent history of homelessness in Dallas-area homeless shelters. Since June 2009, 

37 TB cases belonging to the G10509 genotype cluster have been identified, with 21 (57%) 

reporting recent homelessness.

The Texas Department of State Health Services and Dallas County Department of Health 

and Human Services (DCHHS), with input from CDC, identified two Dallas-area homeless 

shelters as potential sites for ongoing disease transmission. As such, the DCHHS TB 

Elimination program has conducted several mass-screenings for TB disease at the two shelters 

and is working closely with the shelters (and others in the area) to identify and evaluate 

individuals potentially exposed to TB.

In additional response to the ongoing outbreak, a team of epidemiologists from the CDC 

National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP), 

Division of Tuberculosis Elimination (DTBE) conducted an on-site investigation in January, 

2013. In their report dated April 10, 2013, the CDC team included a recommendation to 

improve environmental controls at the homeless facilities implicated in disease transmission. 

On March 21, 2013, the Division of Respiratory Disease Studies (DRDS), National Institute 

for Occupational Safety and Health (NIOSH), CDC received a request for technical 

assistance concerning the TB outbreak in Dallas County. The request was made by the Chief 

Epidemiologist of the DCHHS. The request specifically asked NIOSH to evaluate shelters’ 

heating, ventilation, and air-conditioning (HVAC) systems and make recommendations to 

improve overall environmental controls. The request was initially made for an assessment at 

another Dallas area homeless shelter. However, after subsequent discussions with DCHHS, 

a request for technical assistance was received by DRDS/NIOSH/CDC from the shelter 

manager of this second shelter on May 22, 2013. Thus, a total of two requests were received to 

assess facilities that provide assistance to the homeless and which had epidemiologic links to 

past or ongoing TB transmission.

In response to the two requests for technical assistance, a NIOSH team visited the two 

facilities in June 2013. This report describes the measurements and associated findings from 

our assessment at the second homeless shelter. It details and prioritizes our recommendations 
Health Hazard Evaluation Report 2013-0145-3209 Page 3

for improving environmental controls at the shelter and outlines the current plan for future 

NIOSH involvement. 

Background

Tuberculosis and Homeless Populations 

TB is a disease caused by Mycobacterium tuberculosis (M. tuberculosis) bacteria. When a 

person with active TB disease coughs or sneezes, tiny droplets containing M. tuberculosis

may be expelled into the air. Many of these droplets dry, and the resulting residues remain 

suspended in the air for long periods of time as droplet nuclei. If another person inhales air 

that contains the infectious droplet nuclei, transmission from one person to another may 

occur. Homeless people have been identified as a high-risk population for TB infection and 

disease since the early 1900s [Knopf 1914]. With the increase in homelessness in the United 

States since the 1980s, TB among homeless persons has become a subject of heightened 

interest and concern [CDC 1985; 1992; 2003a,b; 2005a; Barry et al. 1986; Slutkin 1986; 

McAdam et al. 1990; Nolan 1991].

The Homeless Shelter 

The homeless shelter, located in downtown Dallas, TX, was opened in May 2008, by the 

community’s homeless coalition. Unlike many homeless facilities, the shelter consists of 

all recently-constructed buildings designed for the sole purpose of providing services to 

homeless persons. The shelter is a multi-purpose facility based on a unique public-private 

partnership. It is dedicated to serving homeless men and women (≥18 years old), with the 

primary focus being the chronically homeless. Any adult client may access shelter services 

after obtaining a unique shelter identification code, as long as the client does not have active 

arrest warrants with law enforcement agencies.

The large shelter campus is home to three main buildings and a large sleeping pavilion, 

which was converted from an old warehouse. In the center of the campus is a courtyard that 

features large fans, benches and water fountains. The welcome building is an approximately 

10,000 square foot, one-story brick building that houses an intake area, a main reception 

area, counseling offices, a security office, library, laundry room, a women’s day room, a 

phone room, a personal care area, and men’s and women’s restrooms. The welcome building 

provides care management services for more than 600 people experiencing homelessness per 

week, including: jail diversion/reentry services, income seeker services, and housing seeker 

services. All clients seeking services at the shelter must be processed through the welcome 

building.

The campus is also home to a 6700 square foot, one-story brick dining building that contains 

a kitchen, separate small and large dining rooms, men’s and women’s bathrooms, and men’s 

and women’s shower rooms. The dining building currently serves three meals a day, seven 

days a week to more than 700 people per meal.
Page 4 Health Hazard Evaluation Report 2013-0145-3209

The largest building on the campus is a three-story, 40,000 square foot, brick and glass 

services building. The first floor of the building contains medical clinic facilities, including a 

waiting area, admission area, six examination rooms, counseling offices, nursing office, and 

restrooms. The first floor also houses a behavioral clinic waiting, admission, and conference 

room areas, as well as several staff offices, classrooms, and additional restrooms. Combined, 

the clinics provide medical and behavioral care for more than 600 people per week, including: 

screenings, acute disease care, chronic disease care, mental health/chemical dependency/dual 

diagnosis services, and recovery services. The second floor of the services building contains 

the women’s transition dormitory rooms, a kitchenette, as well as a pair of day rooms and 

restrooms for the women housed there. The women’s dormitory area is equipped to sleep 26 

clients nightly. The second floor also houses many client counseling offices and offices for 

shelter administrators. The third floor of the services building contains the men’s transitional 

housing units and subsequent day rooms and bathrooms, as well as the handicap housing area 

and handicap restrooms. The men’s transitional housing units are equipped to sleep a total of 

74 men, up to 14 of which can be housed in special handicap-accessible accommodations.

The sleeping pavilion is an 8600 square foot area with 17-feet tall ceilings. During the day 

this area is utilized by clients as a place to rest and relax while waiting for other shelter service 

appointments. At night, the pavilion accommodates up to 225 people sleeping on mats. Both 

men and women sleep in the pavilion, but in separate areas of the room. Men’s and women’s 

restrooms with shower facilities are also available to clients in the pavilion area of the campus.

Each day, the shelter provides services to approximately 800–850 people. Each night, around 

325 clients spend the night on campus, while nearly 500 others are placed in other Dallas-area 

shelters for the night. During periods of inclement weather, an additional 150 clients can be 

sheltered for the night in overflow areas at the shelter. 

Assessment 

On June 3, 2013, an opening meeting was held at the DCHHS. An update was given on 

the current status of the ongoing TB outbreak among the homeless population, and the 

assessment team provided background information on NIOSH, the nature of the technical 

assistance requests, and the ventilation measurements we planned to collect at each facility. 

Aside from NIOSH and DCHHS staff, representatives from each homeless facility we planned 

to visit during the week were present, as well as a representative from Parkland Hospital in 

Dallas, TX.

We arrived at the homeless shelter on Wednesday, June 5, 2013, and were met by the chief 

services officer, who briefly showed us around the campus and gave us an overview of the 

buildings on site and the services they provided. We were then introduced to the shelter 

manager who led us on a complete in-depth tour of the shelter campus. At the conclusion of 

the tour, we were introduced to the facilities director who served as our point of contact for 

the rest of our on-site assessment.
Health Hazard Evaluation Report 2013-0145-3209 Page 5

We took physical and ventilation measurements in all key areas of the campus, focusing on 

areas where shelter clients typically congregate or spend significant amounts of time. The 

dining areas, main reception areas, and dormitory and day rooms were the areas of primary 

concern. However, we took measurements throughout every building on campus.

We recorded the make and model number of all six air-handling units (AHUs) providing 

supply air to the buildings on campus: three AHUs on the roof of the services building, two 

AHUs on the roof of the dining building, and one AHU on the roof of the welcome building. 

We also visually inspected all of the units. When possible, we measured the air flow rate 

through supply diffusers and return grilles using either a TSI Incorporated (Shoreview, 

Minnesota) Model EBT731Alnor Balometer Capture Hood or a Model 8373 Accubalance 

Plus Air Capture Hood equipped with appropriately-sized capture hoods for the vents/grilles 

being measured. The Model EBT731 measures volumetric air flow rates of 25-2500 cubic 

feet per minute (cfm) with an accuracy of ±3% of the reading plus ±7 cfm for measurements 

above 50 cfm, while the Model 8373 measures volumetric air flow rates of 30-2000 cubic feet 

per minute (cfm) with an accuracy of ±5% of the reading and ±5 cfm. Both air capture hood 

models are equipped with a directional air flow indicator that provides confirmation of flow 

direction. We determined the approximate internal volume of the measured spaces with 

either a standard tape measure or a Zircon Corporation (Campbell, California) Model 58026 

LaserVision DM200 laser distance measuring device. The device accurately measures up to 

200 feet and has function keys for calculating the area and volume of a room for HVAC load 

formulas. When the existence of air flow or the air flow direction was questioned, we used a 

Wizard Stick hand-held fog generator (Zero Toys, Concord, Massachusetts) to qualitatively 

confirm and visualize the air flow pattern.

We completed taking measurements at the shelter campus on Thursday, June 6, 2013. On the 

morning of Friday, June 7, 2013, we met briefly with the services director, facilities director, 

and shelter manager to discuss our general findings from the assessment. An in-person, 

formal closing meeting for our on-site response to the technical assistance requests for 

both homeless facilities was not practical at the time of our visit. Thus, a meeting was held 

via teleconference on Wednesday, June 12, 2013. This meeting provided an opportunity to 

discuss our general findings with representatives from the DCHHS staff. 

Results and Discussion

General Tuberculosis Infection Control

All tuberculosis control programs should include three key components: administrative 

controls (e.g., intake questionnaires and policies), environmental controls (e.g., ventilation 

and filtration), and a respiratory protection program. Ideally, environmental controls and 

respiratory protection should supplement aggressive administrative controls. Detailed 

explanations for each of these key control elements, as well as a discussion on the hierarchy 

of their implementation, are outlined in CDC’s Guidelines for Preventing the Transmission 

of Mycobacterium tuberculosis in Health-Care Settings, 2005 and Prevention and Control of 

Tuberculosis in Correctional and Detention Facilities: Recommendations from CDC [CDC 
Page 6 Health Hazard Evaluation Report 2013-0145-3209

2005b, 2006]. In high risk environments, such as homeless shelters, or in areas where 

administrative controls alone are inadequate, environmental controls and respiratory 

protection should be used as secondary and tertiary levels of control, respectively.

Administrative Controls

During our visit, and in previous conversations with representatives from DTBE, the Texas 

Department of State Health Services, DCHHS, and the shelter, it was apparent that limited 

TB administrative controls were in place at the shelter prior to the current disease outbreak. 

Men and women placed in the transitional housing units were required to undergo TB testing 

prior to receiving a bed in the services building. However, little TB testing was conducted 

on the more transient client population prior to the outbreak. Since then, efforts were taken 

to improve the overall administrative controls in place by the time of the NIOSH site visit. 

Employees and volunteers were trained on symptoms of TB disease and prevention of TB 

transmission. Additionally, intake screening procedures are now in place to help identify 

guests on target screening lists, or others suspected of having TB, and refer them to DCHHS 

for critical medical screening. These procedures will help identify infected individuals more 

rapidly in the future and serve to help keep infected guests away from those that are not 

infected. 

We cannot overstate the importance of having robust administrative controls in place. As 

with most homeless facilities, this shelter provides services to a large number of clients who 

are often in very close proximity to one another. This is particularly the case in the pavilion 

sleeping area, the dining areas during meals, and the main reception area of the welcome 

building during periods of occupancy. Even the best ventilation systems are incapable of 

preventing the spread of infectious disease between clients close to one another, as is often 

the case. Thus, promptly identifying people with suspected disease, keeping them separated 

from the general client population, and following up with appropriate medical evaluations 

and treatment (if necessary) are the most important elements of reducing or eliminating the 

spread of infectious disease.

While enhancing administrative controls is a significant step, the development of a written 

TB Infection Control Plan (ICP) for the shelter should be considered. At the time of the 

NIOSH investigation, no such ICP was reported to exist. Information on creating ICPs 

and useful TB ICP templates, although not specific to homeless shelters, can be found at 

the Curry International Tuberculosis Center website at http://www.currytbcenter.ucsf.

edu/. Collaborating with DCHHS and the Texas Department of State Health Services 

would serve to further strengthen the written plan. These ICPs are particularly useful when 

overall TB infection control requires the coordination and subsequent follow-up of different 

agencies. In response to this current TB outbreak, there was good communication and 

coordination between the shelter and DCHHS. However, the process should be formally 

documented in a protocol or checklist format. This ensures that each time there is a TBrelated incident, all necessary agencies understand their responsibilities and perform their 

assigned predetermined actions in a consistent manner. A written TB ICP should be created, 

understood, and adhered to by all necessary agencies. Incorporating the input of staff 
Health Hazard Evaluation Report 2013-0145-3209 Page 7

involved in the maintenance and operation of facility ventilation systems into the overall 

infection control program can also help strengthen the program. Participation in plan 

development provides these staff members with additional insight as to what ventilation 

requirements are necessary to prevent and/or isolate TB disease and helps to ensure that 

ventilation modifications outlined in the plan are feasible. Input from the ventilation staff 

should be sought during the formal creation of the ICP and during all subsequent revisions to 

the plan.

Environmental Controls

General Ventilation System Information

General information on the AHUs at the shelter, including the areas served by each unit, 

is provided in Table 1. All six of the AHUs were rooftop units produced by McQuay 

International (Minneapolis, Minnesota). All of the AHUs were installed during construction 

of the campus and were 6-7 years old during our visit. The units provided cooling via a 

closed chilled water loop throughout the campus and heating through a separate hot water 

loop. A large chiller and multiple boilers are located on campus to support the AHU cooling 

and heating loads. All of the AHUs were controlled by a modern building automation 

system, including economizer cycles to adjust the amount of outdoor air brought into the 

buildings with changes in outdoor environmental conditions. Economizer cycles should 

generally be used to meet outdoor air requirements to each occupied space under all 

environmental conditions, while maximizing the amount of outdoor air when conditions 

make it economically feasible (i.e., when outdoor conditions are very close to desired indoor 

temperature and humidity setpoints).

Filtration

All six of the shelter AHUs contained sets of properly-sized, four-inch thick disposable panel 

filters from Glasfloss Industries (Dallas, Texas). The Glasfloss Z Line disposable panel filters 

have a published Minimum Efficiency Reporting Value (MERV) of 8. For ventilation air 

filters, the MERV value provides information on the overall filtration efficiency. A MERV 

8 filter corresponds to a single-pass removal efficiency of greater than 70% for 3.0 to 10 

micrometer (μm) particles [ANSI/ASHRAE 2012]. However, MERV 8 filters are less than 

50% efficient at filtering particles in the 1.0–3.0 μm size range, which includes droplet nuclei 

responsible for M. tuberculosis transmission [ANSI/ASHRAE 2012]. 

When part of a M. tuberculosis infection-prevention strategy, air filters should provide 

a removal efficiency of greater than 90% of particles in the 1.0–3.0 μm size range, which 

corresponds to a MERV 13 or higher. During future HVAC design modifications, system 

evaluations, or retrofits, the selection of filters for use in the AHUs should be closely 

examined for the potential to increase filtration efficiency. However, care should be taken 

when choosing more efficient filters, because increased efficiency is typically associated with 

increased pressure drop across the filter (resistance to air flow). Filters in the AHUs should 

have the highest possible efficiency (i.e., highest MERV rating) while still maintaining the air 

flow required for conditioning and outdoor air supply through each system.
Page 8 Health Hazard Evaluation Report 2013-0145-3209

Preventive Maintenance

The ventilation system preventive maintenance program at the shelter was coordinated 

by the facility director. All of the AHUs appeared clean, functional, and well maintained. 

Ventilation filters were reported to be changed monthly. Filter changes and other typical 

AHU maintenance tasks are addressed by maintenance staff employed by the shelter. Outside 

ventilation contractors are also brought in when necessary. Overall, the effectiveness of 

the HVAC preventive maintenance program was impressive, but there was no written plan 

outlining the preventive maintenance schedules and procedures for the shelter HVAC systems. 

A written HVAC Operation and Maintenance (O&M) Plan should be developed. Combining 

all maintenance tasks, schedules, procedures, and training requirements into a written plan 

would help ensure that all equipment is properly maintained at appropriate time intervals and 

that any emergency maintenance issues are addressed correctly. Consultation with the filter 

media manufacturer or their vendor representative(s) should provide the recommended filter 

replacement frequency for inclusion into the O&M plan. A detailed plan would also help 

ensure that the quality of work remains consistent as staff changes over time. Once developed, 

this written plan should be revised periodically to be current with any ventilation system and 

equipment modifications at the facility.

Ventilation Measurements and Indoor Air Quality

An adequate supply of outdoor air, typically delivered through the HVAC systems, is necessary 

within indoor environments to dilute pollutants that are released by equipment, building 

materials, furnishings, products, and people. Chapter 55, Dallas Mechanical Code, of the 

Dallas City Code regulates the “design, construction, quality of materials, erection, installation, 

alteration, repair, location, relocation, replacement, addition to, use, and maintenance of 

mechanical work in the city.” The most recent version of the Dallas Mechanical Code took 

effect on November 1, 2013 (after the NIOSH visit). That version of the Dallas Mechanical 

Code adopted the 2012 edition of the International Mechanical Code, with some minor 

Dallas-specific changes and amendments [City of Dallas 2013; ICC 2012]. When it comes 

to ventilation standards, in most cases, the Dallas Mechanical Code has adopted the same 

recommendations published in American National Standards Institute (ANSI)/ASHRAE 

Standard 62.1-2010: Ventilation for Acceptable Indoor Air Quality (which was in effect at the 

time of the NIOSH survey) and carried over into the more recent ANSI/ASHRAE Standard 

62.1-2013. These ASHRAE recommendations provide specific details on ventilation 

requirements for acceptable indoor air quality in a variety of indoor, occupied spaces [ANSI/

ASHRAE 2013a]. 

The Dallas Mechanical Code and ASHRAE 62.1-2013 recommend outdoor air supply rates that 

account for both people-related and building-related contaminant sources. Specific exhaust 

air flow rate requirements for some spaces are also listed. Although there are no specific 

guidelines for homeless shelters and related facilities, there are applicable published guidelines. 

These outdoor air supply and exhaust air requirements are summarized in Table 2. Table 2 

also lists the default occupant densities for various spaces. These default values, given in terms 

of the number of occupants per 1000 square feet, are provided by the Dallas Mechanical Code

and ASHRAE to assist building and HVAC system designers when actual occupant densities 

are unknown. Although actual occupant densities for the occupied spaces at the shelter 
Health Hazard Evaluation Report 2013-0145-3209 Page 9

are generally known, the default values still serve as a reference to determine whether the 

occupant density in a given space is higher or lower than what is considered typical.

The collected physical and ventilation measurements are presented in Table 3. The third 

column from the right of the table presents the actual occupant densities in each space. 

Values preceded by an asterisk (*) denote areas with occupant densities higher than the 

default values presented in Table 2. High occupant densities are not solely indicative of 

ventilation problems and each case must be examined individually. For example, the pavilion 

sleeping area shows a high occupant density because many people actually sleep in close 

proximity to one another. Several of the offices and the library in the welcome building, and 

many offices throughout the first floor of the services building (including those in the two 

clinics) also show high occupant densities. Much of this is because the offices are smaller 

than what is considered typical. For private offices this would be less of a concern, however, 

many of these areas also represent spaces where shelter staff members could be face-to-face 

with a potentially infectious client. In these cases, special consideration should be given to air 

flow patterns in the spaces to minimize the potential of exhalations from one person passing 

through the breathing zone of multiple other people. This is especially true when airborne 

infectious disease transmission is a concern. 

The second-to-last column in Table 3 presents the outdoor air requirements for each space, 

as established by the Dallas Mechanical Code and ASHRAE. As previously noted, all of the 

AHUs at the shelter are capable of introducing outdoor air into the occupied spaces they serve 

and the amount of outdoor air is controlled by an economizer cycle through the building 

automation system. During our assessment of the shelter AHUs, the outdoor temperature 

was nearly 90°F, and the outdoor air dampers on all of the systems were nearly closed, if not 

closed completely. We did not have instruments that allowed us to accurately quantify the 

amount of outdoor air introduced by each AHU but given the damper positions, the amount 

of outdoor air supplied by each AHU appeared to be consistently less than that prescribed by 

the Dallas Mechanical Code and ASHRAE.

One area of heightened concern was the pavilion sleeping area, since it is not ventilated by a 

mechanical ventilation system. Throughout the campus, the potential for airborne disease 

transmission was of greatest concern in this space given that 225 people (or more) sleep on 

mats in close proximity with limited control over ventilation. The space does include two large 

ceiling fans to help move air and one wall has garage doors with windows removed to allow 

for natural ventilation (even more when the garage doors are raised). Regardless, there was 

no way to verify that appropriate amounts of outdoor air are introduced and well distributed 

throughout the space during periods of high occupancy and under all environmental 

conditions. During our visit to the shelter, we were told that a capital improvement project 

was planned that would install a mechanical ventilation system in the pavilion sleeping area. 

As of February 24, 2014, a new 50-ton AHU has been installed on the roof of the pavilion. 

Installation of ductwork and electrical systems was still ongoing. Assuming the new AHU 

was properly sized to handle conditioning outdoor air under all occupancy and weather 

conditions, then adequate fresh, outdoor air could be supplied to the pavilion sleeping area 

once the system is operational. It will be key however that this outdoor air be distributed 

down low, to the occupied floor area, in order to be of benefit to room occupants. 
Page 10 Health Hazard Evaluation Report 2013-0145-3209

It is important to ensure that all occupied spaces at the shelter are receiving adequate amounts 

of outdoor air to inhibit airborne disease transmission and improve indoor air quality. In 

addition to alleviating odors and better maintaining occupant comfort, outdoor air serves 

to dilute infectious aerosols, such as M. tuberculosis droplet nuclei. While the capacity to 

introduce and temper (i.e., heat or cool and dehumidify) appropriate amounts of outdoor air 

appeared to exist within each AHU, that capacity was not being properly used at the time of 

our assessment. Each AHU should be assessed to ensure that adequate capacity does exist 

to temper the recommended amounts of outdoor air under all periods of occupancy and all 

weather conditions. If so, making necessary adjustments to the HVAC sequence of operations 

could easily ensure sufficient outdoor air to the occupied spaces at all times. 

If the capacity to temper sufficient outdoor air does not exist as the AHUs are currently 

configured, then one of two common approaches could be employed to introduce outdoor 

air into the occupied spaces (or a combination of the two). The first approach would be to 

make the necessary modifications to the existing AHUs to allow them to bring in the required 

outdoor air. This would initially require evaluation, by a knowledgeable HVAC engineer 

(a reputable ventilation or engineering design contractor that is familiar with ASHRAE, 

Facility Guidelines Institute [FGI], and CDC guidelines and recommendations), of each 

AHU’s current conditioning capacity and the amount of additional capacity needed under 

worst-case conditions of occupancy and weather. Once that information is known, various 

modifications to each AHU can be compared to determine the most cost-effective method for 

meeting outdoor air requirements. Potential modifications could range from new cooling and 

heating coils, modifications to operating temperatures in the water supply loops, new fans, 

or some combination of these options. Although incorporating outdoor air into the existing 

AHUs may be the simpler of the two solutions and could require the least capital expense, it 

may cost significantly more in energy over time. At least on hot days, as was the case during 

our assessment, the AHUs are mainly recirculating air that is relatively close to the desired 

indoor temperature and humidity conditions (since only minimal outdoor air was brought 

in). After circulating through the occupied space, this air requires less conditioning to return 

it to the desired delivery temperature and humidity levels. Once significantly more outdoor 

air is mixed with the room return air, the mixed air stream passing through each AHU will be 

further from the desired indoor conditions for most of the year. Each AHU will then need to 

work harder to temper the mixed air stream.

A second method of bringing outdoor air into the shelter would be to install dedicated 

outdoor air systems. This would involve installing a new AHU for each building, with 

ductwork extending to all occupied spaces and dedicated specifically for supplying outdoor 

air. For the welcome building, the new AHU should be sized to provide adequate outdoor air 

flow for the entire building (approximately 1500 cfm) while also providing the entire capacity 

to temper and dehumidify this outdoor air. Similarly, the new AHUs for the dining building, 

services building, and pavilion would need to provide around 1500 cfm, 3700 cfm, and 2000 

cfm of outdoor air, respectively. The new AHUs should provide tempered and dehumidified 

(supercooled to 45–50°F dew point) outdoor air to each space (or existing AHU) in quantities 

necessary to meet Dallas Mechanical Code and ASHRAE outdoor air requirements under 

worst-case conditions. Terminal reheating or blending of this air with air delivered by 
Health Hazard Evaluation Report 2013-0145-3209 Page 11

the primary AHUs may be necessary to prevent thermal discomfort from the supercooled 

outdoor air. Conversely, multiple smaller dedicated outdoor air systems could serve the 

same purpose as one large system for a given building. For example, three small dedicated 

outdoor air systems could be used in the services building, with each tailored to serve only 

one floor. Regardless of how it is accomplished, the primary advantage of the dedicated 

outdoor air systems is that they would not require major modifications to the existing AHUs, 

which would continue to recirculate air through the spaces they serve while providing air 

filtration, heating and cooling. In fact, if the dedicated outdoor air systems are designed 

properly, all of the heating and cooling loads for the required outdoor air could be transferred 

to the new AHUs. This would allow the outdoor air intakes in the existing AHUs to be closed 

permanently. The dedicated outdoor air system approach would certainly require more 

capital expense and more renovations for the required ductwork than the first option, but they 

could also provide significant energy cost savings, making it a more viable long-term solution. 

A knowledgeable HVAC engineer should be consulted to discuss these and other potential 

options for introducing outdoor air into all buildings on the shelter campus. At the same 

time, consideration should be given to optimizing air flow patterns to further protect shelter 

staff from the potential of airborne disease transmission. This is particularly important 

around reception areas in the welcome building and the two clinics in the services building, 

where staff members could come into close contact with guests having unknown cases of 

disease. While even the best ventilation system cannot guarantee prevention of disease 

transmission between people in close proximity to one another, improving air flow patterns 

could help reduce the overall transmission potential. One way that air flow patterns could be 

improved in these areas is to supply all air (fresh and recirculated) above the reception desks 

using supply diffusers designed to discharge the air in a wide, downward deflected angle. At 

the same time, return grills should be moved away from the reception desk to facilitate the 

flow of air from clean areas (the reception desks) to potentially contaminated areas (waiting 

areas). A qualified HVAC/ventilation engineer might recommend other air flow schemes that 

could be similarly effective at providing adequate ventilation while minimizing the potential 

for disease transmission. The final chosen design scheme should be smoke tested to verify 

performance.

During our visit, we collected measurements in the six medical clinic examination rooms 

on the first floor of the services building. Along with the clinic waiting area, these medical 

exam rooms are primary locations where sick and/or infectious clients might be present as 

they seek diagnoses or treatment from medical staff. As such, the waiting area and exam 

rooms should be constantly maintained under negative pressure to the adjacent admissions 

area and corridor, and the pressure relationship should be periodically tested and confirmed 

with a micromanometer or qualitative visual techniques like smoke tubes or flutter strips. 

Our measurements show (see Table 3), and ventilation fog testing confirmed, that the waiting 

area, and exam rooms #1, #2, and #5 were improperly under positive pressure compared to 

the adjacent waiting area. Thus, air from inside these areas was able to migrate out into the 

adjacent spaces. Modifications to the ventilation system should be made to create proper air 

flow patterns so that airborne infectious agents generated inside these spaces are maintained 

inside the space. The correct negative pressure could possibly be established by adjusting 
Page 12 Health Hazard Evaluation Report 2013-0145-3209

existing dampers or ductwork so more air is exhausted from the exam rooms than is being 

supplied to them. Reducing return air and/or increasing supply air from adjacent areas on 

the same HVAC system could further facilitate this approach. If negative pressure cannot 

be maintained with such adjustments, the installation of dedicated exhaust fans within each 

exam room may be required. Depending upon the frequency of patient exams, the dedicated 

exhaust fan approach could be a more energy-efficient option for maintaining negative 

pressure in these areas, as they could be turned on and off as necessary. However, prudent 

administrative or occupancy-automated procedures to ensure their use during patient exams 

would be of primary importance.

The last column in Table 3 provides the recommended exhaust flow rates from occupied 

spaces, when such recommendations exist. Values in this column preceded by an asterisk (*) 

denote areas where the measured exhaust flow rates were less than the recommended rate as 

presented in Table 2. We noticed that exhaust air from most of the bathrooms and shower 

rooms throughout the campus was less than recommended by the Dallas Mechanical Code

and ASHRAE (see Table 3). In fact, the south bathroom (Rooms S208 and S215) for the 

women’s transitional housing dorms and the bathrooms for Unit B and Unit C in the men’s 

transitional housing units were the only ones exhausting appropriate amounts of air from the 

spaces. The bathroom facilities for the guests staying in the pavilion did not have mechanical 

ventilation and did not appear to possess a reliable natural ventilation design scheme. To 

control humidity and odors, bathrooms and shower areas should exhaust more air than the 

AHU is supplying. This will maintain these areas under negative pressure. Separate exhaust 

fans should be used to exhaust air directly outside at least 25 feet from any air intakes. There 

should be no recycling or re-entrainment of return/exhaust air from the bathrooms and 

shower rooms. For high occupancy public bathrooms, the Dallas Building Code and ASHRAE 

Standard 62.1-2013 both include the same exhaust recommendations, but they differ in how 

the recommendations are applied. The Dallas Building Code states that if the exhaust fans are 

operated continuously, 50 cfm per water closet should be exhausted. If the exhaust fans are 

operated intermittently (e.g., fans activated by a light switch), 70 cfm per water closet should 

be exhausted. The ASHRAE Standard 62.1-2013 recommendation for public bathrooms is 

based on expected usage. It states that 70 cfm per water closet should be exhausted when 

periods of heavy use are expected to occur. If periods of heavy use are not anticipated, then 

exhausting 50 cfm per water closet is sufficient. For private toilets in bathrooms intended 

to be occupied by only one person at a time, both codes specify that the exhaust ventilation 

should be 25 cfm if the exhaust fan is designed to operate continuously or 50 cfm if the 

exhaust fan only operates during periods of occupancy (e.g., exhaust fan controlled by a wall 

switch). The exhaust fans in all bathroom and shower areas on the shelter campus should be 

checked to ensure functionality and their exhaust rates should be verified for compliance with 

the Dallas Mechanical Code. [Note: The kitchen hood exhaust systems in the dining building 

were not evaluated at the time of the NIOSH site visit. These systems are not discussed in this 

report.]

While not a major concern from an airborne disease transmission standpoint, temperature 

and relative humidity (RH) 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 
Health Hazard Evaluation Report 2013-0145-3209 Page 13

heat to the environment, physiological adjustments, and body temperature. Heat transfer 

from the body to the environment is influenced by factors such as temperature, humidity, 

air movement, personal activities, and clothing. ANSI/ASHRAE Standard 55-2013: Thermal 

Environmental Conditions for Human Occupancy specifies the combinations of indoor 

thermal environmental and personal factors that produce acceptable thermal environmental 

conditions to a majority of occupants within a space [ANSI/ASHRAE 2013b]. Assuming 

slow air movement (less than 40 feet per minute) and 50% RH, the operative temperatures 

recommended by ASHRAE range from 68.5oF–75oF in the winter, and from 75oF–80.5oF 

in the summer. The difference between the two temperature ranges is largely due to 

seasonal clothing selection. ASHRAE also recommends that RH be maintained at or below 

65% [ANSI/ASHRAE 2013b]. The U.S. Environmental Protection Agency recommends 

maintaining indoor relative humidity between 30–50% because excessive humidity can 

promote the growth of microorganisms [EPA 2012]. Temperature and RH levels were not 

recorded during our visit. Regardless, we recommend maintaining the indoor temperature 

and RH levels within the ranges established by ASHRAE to provide the most comfortable 

environment to shelter clients. 

Respiratory Separation Areas

Currently, the shelter does not have areas set aside for separating clients suspected of having 

TB or other respiratory diseases from the remainder of the guest population. Rapidly 

identifying people with suspected TB disease and keeping them separated from others until 

appropriate medical evaluations and treatments are initiated is one of the most important 

elements in reducing or eliminating the spread of airborne disease. Excluding those clients 

in the transitional housing units, the background and medical status may be largely unknown 

for guests seeking shelter in the pavilion sleeping area. Given this fact, as soon as the new 

mechanical ventilation system is installed and operational, we strongly recommend creating 

an area inside the pavilion (or some other suitable location) which can be used for respiratory 

separation when needed. It is important to recognize that respiratory separation is not an 

alternative to medical evaluation. Rather, it is proposed to be a temporary holding area 

for guests awaiting transport for medical evaluation. It may also be used to house guests 

exhibiting signs of respiratory distress without having identified disease. When respiratory 

separation is not required, the areas can be used for normal clients’ housing, as is typically the 

case.

A respiratory separation area is not intended to be equivalent to an airborne infection 

isolation (AII) patient room found in hospitals and other healthcare settings. However, it 

can be designed using some of the same protective concepts, namely negative room pressure 

and elevated ventilation rates. The respiratory separation area should be maintained under 

negative pressure relative to the adjacent spaces. This means that air from outside the 

respiratory separation area should migrate inwards into the respiratory separation area and 

not in the opposite direction. This is easily maintained by exhausting more air from the 

respiratory separation area than is being supplied. Operable windows, either within the 

respiratory separation area or in adjacent areas, should not be allowed to interfere with this 

intent. Negative pressure helps reduce the potential that a guest housed in the respiratory 

separation area with active TB disease (or any other disease where airborne infection is a 
Page 14 Health Hazard Evaluation Report 2013-0145-3209

concern) could expose other healthy individuals in adjacent areas. In addition to maintaining 

negative pressure, all return air from the respiratory separation area should preferably be 

exhausted directly outside. In no circumstances should air from the respiratory separation 

area be allowed to re-infiltrate the building or go back through an AHU without first having 

passed through a high-efficiency particulate air (HEPA) filter.

For true AII rooms in healthcare facilities, the CDC and FGI recommend a differential 

pressure of > 0.01 inches of water gauge (2.5 Pascals [Pa]) across the closed door between 

the isolation area and adjacent areas [CDC 2005b; FGI 2010]. Although the minimum 

pressure difference needed for maintaining airflow into a room is quite small (about 0.001 

inches of water gauge), the higher prescribed pressure differential is easier to measure and 

maintain as the pressure in surrounding areas changes due to the opening and closing of 

doors, ventilation system fluctuations, and other factors. The FGI and CDC also recommend 

a total of 12 air changes per hour (ACH) through the isolation room (CDC allows 6 ACH for 

existing AII rooms) and at least 2 ACH of fresh outdoor air. True AII rooms are designed 

to house individuals with confirmed respiratory disease. A respiratory separation area at 

the shelter would not be used to house guests with confirmed disease, so it would not be 

necessary to meet the strict air flow and differential pressure requirements detailed above. 

However, knowledge of the AII design strategies could be useful in designing a respiratory 

separation area. It is vastly more important to establish a negative pressure area that can be 

used for respiratory separation than it is to focus on the respiratory separation area meeting 

quantitative ventilation requirements.

Since the pavilion houses all guests in the same large, open sleeping area, ideally a small room, 

complete with its own solid ceiling, should be constructed in a far, rear corner (away from the 

wall that contains the garage doors) specifically for respiratory separation. Having a sealed, 

separate room would allow the space to be used for separation purposes by: 1) installing 

a new dedicated exhaust fan through the outside wall of the room to provide the required 

exhaust air flow when the room was in use for respiratory separation, and 2) installing tightclosing dampers (or some other mechanism) to completely seal all air returns from the room 

to the new pavilion AHU (if you would choose to provide mechanical ventilation to the space 

with the new pavilion AHU). An exhaust fan should be chosen that is capable of maintaining 

the room under negative pressure relative to the adjacent, larger pavilion sleeping area at 

all times, with minimal noise. The fan could be mounted directly in the wall or on the roof 

with ductwork running through the wall and up to the fans on the outside of the shelter. It is 

imperative that exhaust air from the new exhaust fans is directed away from all current/future 

AHU air intakes and gathering areas outside the shelter.

When a client checks in for night shelter and while presenting symptoms of respiratory 

disease, they should be allowed to sleep inside the new respiratory separation area until they 

can be evaluated by medical personnel. To prepare the room for respiratory separation, 

the room’s dedicated exhaust fan should be activated to maintain the space under negative 

pressure. When respiratory separation is not required, the room can be used for another 

purpose (e.g., storing sleeping mats) by simply deactivating the exhaust fan.
Health Hazard Evaluation Report 2013-0145-3209 Page 15

If construction of a separate room inside the pavilion is impractical, an alternative (but lessdesirable) approach is to install impervious retractable partitions (e.g. accordion-type room 

dividers) that could be used to enclose a far, rear corner of the sleeping area when respiratory 

separation is warranted. The partitions should touch the floor and extend as close to the roof 

deck as possible. An exhaust fan would need to be installed through one of the solid outside 

walls enclosed by the partitions. Again, the fan could be mounted directly in the wall or 

on the roof with ductwork running through the wall and up to the fan on the outside of the 

building. Since there would be more leakage into the separation area around the partition 

walls, and because of the high ceiling in the pavilion, a larger fan would likely be required to 

maintain negative pressure over that required for a solid room. One way to reduce the size 

of the exhaust fan would be to install a small false ceiling that the retractable partitions could 

seal around, thus reducing the overall volume of the separation area.

If a retractable partition enclosure is selected for respiratory separation, the partitions should 

fit as snug to the floor and ceiling as possible. The new exhaust fan should be activated to 

maintain the enclosed space under negative pressure any time the space is used for separation 

purposes. For the majority of the time, when respiratory separation is not required, the 

corner of the room can be used as normal by shutting down the exhaust fan and pushing the 

retractable partitions out of the way.

For any respiratory separation area, a written plan for testing and operating the space is 

strongly recommended. At the shelter, a detailed written plan should be developed for the 

rapid conversion of the space from standard usage to use for respiratory separation. The plan 

should include steps for cleaning and refurnishing the area for separation purposes, and stepby-step procedures for shelter staff to follow to effectively initiate respiratory separation.

When occupied for separation purposes, all respiratory separation areas should be visually 

tested daily to ensure negative pressure is being maintained. Testing can be done cheaply 

and easily with tissue flutter strips or smoke tubes. The results of the testing should be 

documented each day when in use. When the spaces are being used for other purposes, they 

should be tested a minimum of once per month to ensure proper operation in the event they 

would be needed for respiratory separation.

In addition to providing respiratory separation for a shelter guest staying overnight in the 

pavilion area, it could also serve as an area to temporarily separate a guest presenting in the 

welcome center with symptoms of disease during the day. If this arrangement is not feasible, a 

separate respiratory separation area could be established inside the welcome building itself.

Auxiliary HEPA Filtration

The higher the dilution ventilation rate within a given respiratory separation area, the faster 

the room air will be cleared of existing airborne pathogens. In order to increase effective 

ventilation within a separation area, in-room HEPA filtration units may be used. These units 

may be portable or permanently-mounted within the space. Some models can be ceiling 

mounted, which could reduce the potential for tampering. If such units are used, their 

placement and discharge orientation must be selected, installed, and maintained carefully 
Page 16 Health Hazard Evaluation Report 2013-0145-3209

to maximize room air mixing effectiveness without disrupting the desired flow of air into 

the respiratory separation area. These criteria become even more important if a retractable 

partition enclosure is used to establish a respiratory separation area.

One unique use of portable HEPA filtration units is through the use of a ventilated headboard. 

The ventilated headboard is a NIOSH-developed technology that consists of lightweight, 

sturdy & adjustable aluminum framing with a retractable plastic canopy sheeting that can 

extend over the pillow area of a cot, mat or bed. Low-velocity airflow into the canopy is 

created using a high-efficiency fan/filter exhaust unit. This local control technique allows for 

near-instant capture of aerosol originating from the patient while simultaneously providing 

air cleaning to the entire room. NIOSH engineers are available to provide additional 

information or to assist in the selection and acquisition of ventilated headboards. 

Ultraviolet Germicidal Irradiation

Ultraviolet germicidal irradiation (UVGI) is the use of ultraviolet (UV) energy 

(electromagnetic radiation with a wavelength shorter than that of visible light) to kill or 

inactivate viral, bacterial, and fungal organisms. The UV spectrum is commonly divided 

into UVA (wavelengths of 400-315 nm), UVB (315-280 nm), and UVC (280-200 nm). The 

entire UV spectrum can kill or inactivate microorganisms, but UVC energy provides the 

most germicidal effect, with 265 nm being the optimum wavelength [ASHRAE 2011, 2012]. 

Modern UV lamps primarily create UVC energy at a near-optimal 254 nm by electrical 

discharge through low-pressure gas (including mercury vapor) enclosed in a quartz tube. 

UVC from mercury lamps is often referred to as UVGI to denote its germicidal properties. 

Although UVC is invisible to the human eye, small amounts of energy released at visible 

wavelengths produce the blue glow commonly associated with UVC lamps.

Research has demonstrated that UVGI is effective in killing or inactivating M. tuberculosis

under experimental conditions [Riley et al. 1957, 1962; Riley and Nardell 1989; Xu et al. 

2003]. UVGI has also proven effective in reducing the transmission of other infectious agents 

in hospitals, military housing units, and class rooms [Willmon et al. 1948; Wells and Holla 

1950; McLean 1961]. Due to the results of controlled studies and the experiences of clinicians 

and engineers, UVGI has been recommended as a supplement to other TB infection-control 

and ventilation measures to kill or inactivate M. tuberculosis [David 1973; Riley et al. 1976; 

CDC 2005b, NIOSH 2009].

Representatives from the shelter have reported that the new 50-ton AHU being installed 

above the pavilion sleeping area is equipped with an in-duct air disinfection system designed 

to inactivate M. tuberculosis as it travels through the ventilation system. Actual design details 

are unknown to NIOSH at this time; however, if appropriately designed and maintained, 

this in-duct UV system, coupled with particulate filtration, may provide a higher “effective” 

filtration rate than filters alone. The new in-duct UV system represents a prudent control that 

may help prevent the spread of airborne disease among clients in the pavilion sleeping area.

The addition of a well-designed upper-room UVGI system could provide additional 

protection to pavilion clients at the shelter. In congregate settings typical in homeless shelters 

and healthcare facilities, upper-room UVGI systems (often called upper-air systems) are 
Health Hazard Evaluation Report 2013-0145-3209 Page 17

often used to interrupt the transmission of airborne infectious pathogens within the occupied 

spaces themselves. Upper-room UV lamp fixtures are suspended from the ceiling and/or 

mounted on walls at a minimum height of 7 feet above the floor (Figure 2) [Riley and Nardell 

1989; Brickner et al. 2003; NIOSH 2009; ASHRAE 2011, 2012]. Lamps are shielded to direct 

radiation upward and outward to create an intense zone of UVC in the upper portion of the 

room while minimizing UVC levels in the lower occupied spaces. These fixtures inactivate 

airborne microorganisms by irradiating them as air currents move them into the path of the 

UV energy. Some upper-room lamp fixtures utilize small fans to enhance air mixing (right 

photograph in Figure 2) [First et al. 1999a,b; CDC 2005b; NIOSH 2009; ASHRAE 2011, 

2012]. The overall effectiveness of upper-room UVGI systems improves significantly when 

the space is well mixed [Riley and Nardell 1989; Brickner et al. 2003]. Although convection 

air currents created by occupants and equipment can provide adequate air circulation in some 

settings, mechanical ventilation systems and/or ceiling fans that maximize air mixing are 

preferable. Floor fans can also be placed in the room to ensure adequate mixing.

Application and placement criteria for upper-room UV fixtures are provided in various 

publications, and manufacturer-specific advice on placement and operations should 

always be followed [First et al. 1999a,b; Riley and Nardell 1989; Brickner et al. 2003; CDC 

2005b; NIOSH 2009; ASHRAE 2011, 2012]. For decades, a rule of thumb for upper-air 

installations has been one 30-watt (nominal input) fixture for every 200 square feet of 

floor space to be irradiated [Riley and Nardell 1989]. Many effective systems have been 

designed to this criterion, yet it is important to note that not all 30-watt lamps provide the 

same output of UVC energy. Ultimately, UVC output is dependent on the type of lamp, the 

lamp manufacturer, the ballast used to power the lamp, the complete fixture design, and 

other factors. A more recent study has suggested installing fixtures to maintain a uniform 

UV distribution of around 30-50 microwatts of UVC energy per square centimeter (μW/

cm2) in the upper portion of the room [Xu et al. 2003]. While essentially “normalizing” the 

recommended output over all lamps and fixture designs, this level of irradiance should be 

effective at inactivating most airborne droplet nuclei containing Mycobacterium, and would 

presumably be effective for inactivation of most viruses as well. Using the results of the 

Xu et al. study, NIOSH developed guidelines for designing upper-room UVGI systems for 

controlling the spread of tuberculosis [NIOSH 2009]. While the guidelines were specifically 

targeted for healthcare settings, they are just as applicable to congregate sleeping areas in 

homeless facilities.

We recommend consulting with a qualified UVGI fixture manufacturer or system engineer, 

familiar with the NIOSH upper-room UVGI guidelines, to design and install an upper-air 

UVGI system in the pavilion sleeping area. The 17-feet ceiling height in that space provides 

an excellent opportunity to utilize a variety of commercially-available fixtures to create a large 

irradiance zone in the upper portion of the room. The ability to mount the fixtures at higher 

heights will also help prevent the fixtures from being tampered with. The two large ceiling 

fans will also provide air mixing within the entire space that is critical for optimum upper-air 

UVGI system performance. Representatives from the shelter also reported that an upperroom UVGI system is currently being installed inside the large reception area in the welcome 

building. Another area where upper-air UVGI should be considered is the main large circular 
Page 18 Health Hazard Evaluation Report 2013-0145-3209

dining area in the dining building. Like the pavilion sleeping area, these spaces have relatively 

tall ceilings that would help maximize UVGI effectiveness while minimizing the likelihood 

of guests tampering with the lamp fixtures. All of the upper-air UVGI systems should be 

designed to provide UV irradiance levels of at least 30-50 μW/cm2 in the upper portion 

of the room while limiting UVC exposure to occupants in the space. If desired, NIOSH 

engineers are available to review proposed UVGI design strategies prior to their purchase and 

installation.

In humans, UVGI may be absorbed by the outer surfaces of the eyes and skin. Shortterm overexposure may result in photokeratitis (inflammation of the cornea) and/or 

keratoconjunctivitis (inflammation of the conjunctiva). The NIOSH Recommended Exposure 

Limit (REL) for ultraviolet irradiation (254 nm) is 6.0 millijoules per square centimeter (mJ/

cm2) for an 8-hour exposure time [NIOSH 1972; ACGIH 2012]. This REL corresponds to a 

maximum continuous exposure of 0.2 μW/cm2 of irradiation to a person inside the room over 

the 8-hour period. If periods of longer potential exposures are anticipated, the measured UV 

irradiance in the lower portion of the room should be lower than 0.2 μW/cm2. The NIOSH 

guidelines clearly explain calculating permissible exposure times given actual irradiance levels 

in the occupied zone. Actual UVC irradiance levels in the occupied portion of the room, 

along with corresponding permissible exposure times, should be measured and documented 

by the system designer/installer prior to initial system use.

Once the upper-air UVGI system is in place and working properly, the fixtures should be 

operated any time occupants are in the pavilion sleeping area. It is preferable to operate the 

system 24 hours a day every day. As with any environmental control system, the new upperair UVGI system will require periodic maintenance. The output from UV lamps naturally 

decreases over time as the lamps are burned. Frequently turning the lamps off and on also 

shortens the useful life of the lamps. The UV output from lamps will also decrease due to 

accumulated dust. Therefore, lamps should be inspected periodically (e.g., quarterly) and 

cleaned when necessary. UV lamps are typically cleaned by wiping the lamp tubes with 

isopropyl alcohol (rubbing alcohol) and a clean, lint-free cloth. Cleaning the lamps with 

water can result in smearing of the dust that can further reduce lamp performance. The 

fixtures housing the UV lamps should be inspected and cleaned as well. Typical UVGI lamps 

are rated for around a year of continuous use. Lamps should be replaced annually, or in 

accordance with appropriate manufacturer recommendations.

IMPORTANT SAFETY PRECAUTION: All UVGI systems must be inactivated before 

workers enter the irradiated upper portion of the space. All maintenance personnel that 

might spend time in the pavilion sleeping area should be trained in exposure hazards posed 

by the UVGI fixtures. Employees responsible for lamp and fixture maintenance should 

receive additional safety training, including appropriate lockout/tagout procedures to prevent 

accidental UV exposures during maintenance tasks. All initial maintenance and training 

requirements should be explained by the UVGI system designer/installer. The required 

maintenance tasks and service logs, along with training requirements and logs should be 

included in the written O&M plan recommended above. A subcomponent of this plan should 

include a UVGI safety plan. Complete information on upper-room UVGI system design, 
Health Hazard Evaluation Report 2013-0145-3209 Page 19

operation, maintenance, and safety can be found in the NIOSH guideline document available 

online at: http://www.cdc.gov/niosh/docs/2009-105/pdfs/2009-105.pdf [NIOSH 2009].

Respiratory Protection

During an outbreak of airborne infectious disease, there could be instances when shelter 

staff members or volunteers find themselves in close contact with guests suspected of being 

infectious. Ideally, these cases would be identified during the administrative screening 

process and appropriate precautions initiated, but when these circumstances cannot be 

avoided, it is wise to consider the availability of respiratory protection to protect staff 

and volunteers. The first step toward the implementation of respirator use is to develop a 

document that clearly outlines a formal respiratory protection program. The Occupational 

Safety and Health Administration (OSHA) Respiratory Protection standard (29 Code of 

Federal Regulations [CFR] 1910.134) outlines the requirements for comprehensive respiratory 

protection programs. In accordance with 29 CFR 1910.134, a written Respiratory Protection 

Program, with an identified program administrator, is required for any facility that requires 

employees to wear respirators. The program must include training, medical evaluations, and 

respirators at no cost to employees or staff required to wear respirators on the job. Initial 

fit testing by a trained individual is required for all employees that will potentially wear a 

respirator. Annual fit testing is required after that, with additional fit testing upon major 

changes to the facial features of the respirator user (i.e. major weight gain/loss, change in 

facial hair, scarring, etc.). 

To comply with applicable OSHA regulations regarding respiratory protection, we 

recommend that the shelter create a written respiratory protection program as outlined in 29 

CFR 1910.134, appoint a program administrator, and initiate training and initial fit testing 

for employees. Many online resources exist to assist in the development of a respiratory 

protection program. OSHA has published a Respiratory Protection informational booklet 

online (http://www.osha.gov/Publications/OSHA3079/osha3079.html) and a more detailed 

Small Entity Compliance Guide for the Revised Respiratory Protection Standard (http://

www.osha.gov/Publications/3384small-entity-for-respiratory-protection-standard-rev.pdf) 

to explain all parts of an appropriate respiratory protection program and how to comply. 

The Small Entity Compliance Guide also contains a sample respiratory protection program 

in Attachment 4 that can be used as a model program. The Washington State Department 

of Labor and Industries has also developed a user-friendly, fillable template that is helpful 

in developing a respiratory protection program at http://www.lni.wa.gov/Safety/Basics/

Programs/Accident/Samples/RespProtectguide2.doc.

The DCHHS, Texas Department of State Health Services, local healthcare facilities or fire/

ambulance stations can potentially assist with training and fit testing the employees required 

to wear respirators. Alternatively, qualitative fit testing kits (BitrixTM) can be purchased for 

around $200.00 each. One kit would likely be enough to conduct all necessary fit testing 

at the shelter for an entire year or more. When paired with a trained and competent fit test 

administrator (see 29 CFR 1910.134), these kits would allow cost-effective, on-site fit testing 

annually.
Page 20 Health Hazard Evaluation Report 2013-0145-3209

Conclusions 

Since the increase in cases of TB disease in 2009, the shelter has taken significant steps to 

improve the administrative controls at the shelter. The shelter has developed important 

lines of communication with DCHHS and improved staff training and awareness of TB 

symptoms. Identifying guests with symptoms of TB disease or those listed on the DCHHS 

target screening lists will help further reduce the potential for future cases of TB disease and 

bring the ongoing outbreak under control. Having consistent protective strategies upon 

suspect case identification is also important. While enhanced administrative controls are now 

in place, there was no written ICP established for the campus, and shelter administrators are 

encouraged to promptly coordinate with DCHHS and the Texas Department of State Health 

Services to establish one. 

Overall, the campus was clean and well maintained. From an environmental control 

perspective, the six rooftop AHUs servicing the welcome building, dining building, 

and services building were all operational, well maintained, and fitted with proper filter 

configurations during our visit. The HVAC preventive maintenance program in place at 

the shelter is managed by the current facility manager and his maintenance staff. While the 

results were impressive, developing a written preventive maintenance or O&M plan for the 

shelter AHUs would further strengthen the preventive maintenance program, particularly as 

staff members change. 

The amount of outdoor air distributed to each occupied space by each AHU is controlled 

by a modern building automation system, including economizer cycles. We were unable 

to accurately determine the amount of outdoor air being introduced by each AHU, but 

given the damper positions witnessed, the amount of outdoor air appeared to be less than 

that required by the Dallas Mechanical Code and ASHRAE guidelines. Additionally, the 

pavilion sleeping area was not ventilated by a mechanical ventilation system at the time of the 

NIOSH survey. Given the number of guests served at the shelter and the close proximity of 

guests to one another within many of the occupied spaces, it is important that these spaces 

consistently receive adequate amounts of outdoor air. In addition to alleviating odors and 

better maintaining occupant comfort, outdoor air serves to dilute infectious aerosols, such as 

M. tuberculosis droplet nuclei responsible for TB transmission. With renovations, the existing 

AHUs might be made to provide the necessary outdoor air, or they could be augmented with 

the installation of new, dedicated outdoor air systems to provide the necessary outdoor air. 

A knowledgeable HVAC engineer should be consulted to discuss options for introducing 

outdoor air throughout the shelter complex. At the same time, consideration should be 

given to improving the air flow patterns in the various living and sleeping areas within the 

complex. Once these changes have been implemented, other ventilation equipment and/or 

supplemental ultraviolet germicidal irradiation systems could be investigated if additional 

environmental controls are desired.

During our visit, we learned that the men and women housed in the transitional housing 

units on the second and third floors of the services building were required to undergo TB 

testing prior to placement in the program. However, the shelter did not have an area set aside 
Health Hazard Evaluation Report 2013-0145-3209 Page 21

for separating more transient, overnight guests suspected of having TB or other respiratory 

diseases from the remainder of the guest population. The background and medical status of 

these overnight guests may be largely unknown. Therefore, it would be prudent to modify 

an area in the pavilion sleeping area for use as a respiratory separation area in the event 

an overnight guest presented with symptoms of respiratory infection. When respiratory 

separation is not required, the area could be used for some other purpose. 

The pavilion sleeping area houses approximately 225 guests, or more, nearly every night. 

Given the occupant density, along with the benefit of the 17-feet ceiling height, a complete 

upper-room UVGI system could be installed in the space to further reduce the potential for 

airborne disease transmission. A qualified UVGI system designer or fixture manufacturer 

should be consulted for options. The system should be designed, operated, and maintained in 

accordance with NIOSH guidelines available online at: http://www.cdc.gov/niosh/docs/2009-

105/pdfs/2009-105.pdf [NIOSH 2009]. Upper-air UVGI systems should also be considered 

for the main reception area of the welcome building and the large dining room in the dining 

building. Once all changes and improvements to environmental controls at the shelter have 

been implemented, the shelter should develop a written preventive maintenance or O&M plan 

for the shelter. 

For instances where improvements to administrative and environmental controls do not 

sufficiently mitigate the risk for disease transmission, respiratory protection might be 

necessary. There was no formal respiratory protection program in place during our visit, 

but such a program should be implemented at the shelter. Having this program in place will 

provide additional protection to shelter staff and volunteers working in close proximity to 

guests with suspected TB or other airborne diseases. All respirator use at the shelter should 

be covered by an OSHA-mandated respiratory protection program.

Administratively, a positive approach is being taken toward reducing the likelihood of future 

TB transmission at the shelter. However, the ventilation systems need some attention to 

further reduce the risk. While ventilation systems and other environmental control systems 

cannot guarantee prevention of future TB disease transmission, improving the environmental 

controls will reduce the potential for airborne disease transmission, along with providing 

better indoor air quality throughout each building. The following recommendations are 

aimed at improving the overall infection control program at the shelter, with emphasis on 

improvements to the existing environmental controls so they meet all applicable standards 

and guidelines.

Recommendations 

Based on our assessment of environmental controls at the shelter, we have developed the 

following list of recommendations, in order of priority:

1. Continue to improve and enhance the TB administrative controls at the complex 

and develop a written Infection Control Plan.
Page 22 Health Hazard Evaluation Report 2013-0145-3209

•	 Continue working with the DCHHS to screen campus staff, volunteers, and 

guests for TB disease.

•	 With input from DCHHS, develop specific procedures for handling a 

suspected or confirmed case of TB disease.

•	 Continue educating staff and volunteers on the signs and symptoms of TB 

disease so they can readily identify suspect cases and implement established 

precautions.

•	 Consider displaying informational posters about TB signs and symptoms to 

educate guests.

•	 Consider displaying signs encouraging proper cough etiquette and hand 

hygiene.

•	 Develop a formal written TB Infection Control Plan. Seek guidance and input 

from DCHHS and the Texas Department of State Health Services. The plan 

should include:

	All aspects of the TB infection control program and associated 

responsibilities (to include reasonable scenarios of guests presenting 

with symptoms and associated response requirements), especially those 

functions requiring coordination with other agencies, such as the local 

and state health departments.

	The improved administrative controls put in place at the shelter since 

the beginning of the TB outbreak.

	Input from ventilation staff and/or guests tasked with servicing 

ventilation systems. Obtaining input from ventilation maintenance 

staff serves to strengthen the environmental control section of the plan 

while giving maintenance staff additional insight into the ventilation 

requirements for reducing or preventing airborne disease transmission.

	Schedule for updating and revising the ICP.

2. Create a respiratory separation area in the pavilion sleeping area.

•	 Choose a reputable ventilation or engineering design contractor that is familiar 

with current Dallas Mechanical Code, ASHRAE, FGI, and CDC guidelines and 

recommendations. Ideally a small enclosed room should be constructed in a 

far, rear corner of the sleeping area specifically for respiratory separation. If 

construction of a separate room is impractical, a less-desirable approach is to 

install impervious retractable partitions that could be used to enclose a corner 

of the sleeping area when respiratory separation is warranted. The partitions 

should touch the floor and extend as close to the ceiling as possible. While 

there are various ways to develop a respiratory separation area, it should 

include the following:

	Ensure that all supply and return ductwork for the AHU serving the 

newly-constructed room or area enclosed by partitions (if any) is 

intact and sealed. Install tight-sealing return dampers on each return 

from the room or enclosure (if any) to eliminate return air flow when 

the space is used for respiratory separation. Ensure that supply air 

diffusers provide good air mixing and air flow patterns in a newly-
Health Hazard Evaluation Report 2013-0145-3209 Page 23

constructed room.

	Design and install an auxiliary exhaust system that enables the 

respiratory separation area to be maintained under negative pressure 

when housing guests for separation purposes. One approach to 

this requirement would be to select and install exhaust fans directly 

through the outside wall of the room or space enclosed by partitions. 

The fan can be mounted through the wall itself or mounted on the roof 

with ductwork through the wall to the fan.

	Install the highest efficiency air filters in the AHU that will still allow 

adequate airflow to meet the AHU’s conditioning requirements. Adjust 

and balance the system as necessary to ensure proper air flows at all 

times when the room or curtain enclosure is used for respiratory 

separation and normal purposes. Ensure that adequate outdoor air is 

supplied to each space at all times (see Recommendation 7 below).

	Develop a detailed written plan for the conversion of the room or 

partition enclosure from normal functions to use for respiratory 

separation. The plan should include:

•	 Procedures for staff to follow to establish the respiratory 

separation area (if partitions are used), start the exhaust fan, 

close the return air dampers (if any), and test for negative 

pressure.

•	 Measures for preparing the area for back-to-back occupants 

requiring separation.

•	 Procedures for cleaning and returning the area to normal use 

after the need for respiratory separation has passed.

	Operate the new system as designed and according to the written plan. 

When in use, the respiratory separation area should be visually tested 

with smoke tubes or flutter strips daily to ensure negative pressure is 

being maintained while the space is occupied for separation. When the 

area is being used for normal purposes, it should be tested monthly to 

ensure proper operation in the event it would be needed for respiratory 

separation. The results of all pressure testing should be documented.

3. Make necessary ventilation changes so all medical clinic examination rooms 

are properly maintained under negative pressure in relation to the adjacent 

waiting area. Negative pressure might be established by adjusting existing dampers 

or ductwork so more air is exhausted from the exam rooms than is being supplied 

to them. If negative pressure cannot be maintained with such adjustments, the 

installation of separate exhaust fans from each space may be required. If new exhaust 

fans are required, they should be operated any time the examination rooms are 

occupied.

4. Repair, replace, or install new bathroom exhaust fans. Ensure that air is being 

exhausted from each bathroom and shower facility and that each area is under 

negative pressure, in accordance with the Dallas Mechanical Code and ASHRAE 
Page 24 Health Hazard Evaluation Report 2013-0145-3209

requirements. Ensure that all exhaust air from bathrooms and shower facilities is 

exhausted directly outside and that no return air from bathrooms is recirculated back 

to an AHU or entrained in the outdoor air entering any current or future AHU.

5. Develop a comprehensive, written HVAC O&M plan. This plan should be updated 

as improvements to HVAC systems are being made. The O&M Plan should include:

•	 Preventive maintenance schedules and all regularly scheduled maintenance 

tasks (filter changes, fan belt inspections, UV lamp changes, etc.) and who is 

responsible for conducting each task.

•	 Written procedures for each maintenance task to ensure the work is done 

properly each time, regardless of who performs the work.

•	 Training requirements for maintenance staff.

•	 A method for logging maintenance activities for each AHU.

•	 A method for updating or revising the O&M Plan as procedures or systems 

change.

6. Install an upper-room UVGI system in the pavilion sleeping area.

•	 Choose a qualified UVGI fixture manufacturer or system engineer, familiar 

with the NIOSH upper-room guidelines, to design, install and test the 

system. The system designer/installer should also provide initial training 

on exposure hazards, safety, and system maintenance.

•	 The system should be designed to provide UV irradiance levels of at least 

30–50 μW/cm2 in the upper portion of the room while limiting UVC 

exposure to occupants in the area to a level below the NIOSH REL for 

UVC of 6.0 mJ/cm2 for an 8-hour exposure time.

•	 Operate the upper-room UVGI system all day, every day, or at least at all 

times the pavilion is occupied.

•	 Establish a UVGI safety, operation, and maintenance program.

•	 Conduct training and maintenance in accordance with NIOSH guidelines 

(http://www.cdc.gov/niosh/docs/2009-105/pdfs/2009-105.pdf) [NIOSH 

2009] and/or applicable manufacturer recommendations.

7. Introduce the required amounts of fresh outdoor air to all occupied spaces under 

all occupancy and environmental conditions.

•	 There are multiple options that can allow adequate outdoor air to be supplied 

to the occupied spaces of the campus. If capacity exists in the current AHUs, 

the easiest method would be to make necessary adjustments to the existing 

HVAC sequence of operations so that appropriate amounts of outdoor air are 

brought in at all times. Other options are also available and discussed in this 

report. All options, including the associated capital, maintenance, and annual 

operating costs should be considered. Work with a reputable ventilation or 

engineering contractor familiar with the current Dallas Mechanical Code, 

ASHRAE, FGI, and CDC guidelines to select the best option for the shelter.

•	 Improve air flow patterns within all occupied spaces, particularly around 

reception areas in the welcome building and the two clinics in the services 
Health Hazard Evaluation Report 2013-0145-3209 Page 25

building. Air flow patterns should provide effective ventilation and 

temperature control while flowing from clean areas to areas more likely to be 

contaminated.

8. Improve filtration efficiency in all AHUs. Select higher efficiency filters (higher 

MERV ratings) for use in each AHU, as long as the new filters do not adversely impact 

the required air flow delivery capacity of the AHUs.

9. Develop and implement an OSHA respiratory protection program in accordance 

with 29 CFR 1910.134. To meet the OSHA requirements, you must:

•	 Designate a program administrator who is qualified by appropriate training 

or experience to administer or oversee the program and conduct the required 

program evaluations.

•	 Provide respirators, training, and medical evaluations at no cost to employees 

or staff required to wear respirators on the job.

•	 Develop a written program with worksite-specific procedures when respirators 

are necessary or required by the employer. The written respiratory protection 

program needs to include:

	Respirator types and proper respirator selection.

	Required medical evaluations for employees prior to respirator use.

	Procedures for initial and annual respirator fit testing.

	Instructions for proper respirator use.

	Information on appropriate respirator maintenance and care.

	Initial and yearly training requirements for respirator users.

	Procedures for evaluating the effectiveness of the respiratory protection 

program.

•	 Update the respiratory protection program as necessary to reflect changes in 

workplace conditions that affect respirator use.

Outline of Future NIOSH Involvement

This report will serve to close out NIOSH Technical Assistance at the shelter. However, we 

understand that the work outlined in the recommendations above will take several months to 

complete and will represent a significant investment of time and financial resources. As the 

work proceeds, NIOSH could assist by:

● Reviewing Requests for Proposal developed to initiate the bidding process.

● Reviewing bids received in response to Requests for Proposals for technical 

content.

● Providing technical assistance related to environmental control strategies, 

including upper-room UVGI systems.
Page 26 Health Hazard Evaluation Report 2013-0145-3209

It is not necessary for NIOSH to be on-site during ventilation renovations. Yet, as projects are 

initiated, we can assist you by reviewing:

● Proposed modification strategies for outdoor air introduction or respiratory 

separation area designs.

● Preliminary design schematics or equipment selection documents. 

● Air flow testing and balancing reports.

Once the renovations are complete, if additional NIOSH assistance is desired or warranted, 

the request for technical assistance can be reopened.
Health Hazard Evaluation Report 2013-0145-3209 Page 27

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Page 30 Health Hazard Evaluation Report 2013-0145-3209 Tables Table 1. General air-handling unit (AHU) information NIOSH AHU Identifier Physical Location of AHU (floor/building) Main Location Served by AHU (floor/building)A AHU ManufacturerB AHU Model NumberB Proper Filter Configuration in AHUC,D Actual Filter Configuration in AHUB,D AHU-D1 Roof of Dining Building Large and Small Dining Areas of Dining Building McQuay OAH021GDAC (4) 20×24×4 & (4) 20×20×4 (4) 20×24×4 & (4) 20×20×4 AHU-D2 Roof of Dining Building Kitchen in Dining Building McQuay OAH021GDAC (4) 20×24×4 & (4) 20×20×4 (4) 20×24×4 & (4) 20×20×4 AHU-S1 Roof of Services Building Entire first floor of the Services Building McQuay OAH030GDAC (8) 20×24×4 & (4) 12×24×4 (8) 20×24×4 & (4) 12×24×4 AHU-S2 Roof of Services Building Entire second floor of the Services Building McQuay OAH030GDAC (8) 20×24×4 & (4) 12×24×4 (8) 20×24×4 & (4) 12×24×4 AHU-S3 Roof of Services Building Entire third floor of the Services Building McQuay OAH046GDAM (12) 20×24×4 & (3) 24×24×4 (12) 20×24×4 & (3) 24×24×4 AHU-W1 Roof of Welcome Building Entire Welcome Building McQuay OAH030GDAC (8) 20×24×4 & (4) 12×24×4 (8) 20×24×4 & (4) 12×24×4 A May not represent all locations served by the AHU. B Information collected during visual inspection of AHU. C Information gathered from product data specific to each AHU model published by respective AHU manufacturer. D Value in parenthesis represents the number of filters; dimensions are width × height × depth in units of inches.
Health Hazard Evaluation Report 2013-0145-3209 Page 31 Table 2. Applicable outdoor air supply flow rates, minimum exhaust air flow rates, and default occupancy densities from the Dallas Building Code (Chapter 55, effective November 1, 2013) and ASHRAE Standard 62.1-2013A Occupancy Category People Outdoor Air Flow Rate (cfm/person)B Area Outdoor Air Flow Rate (cfm/ft2)C Minimum Exhaust Air Flow RateD Default Occupant Density (#/1000 ft2)E Barracks/Dormitory Sleeping Areas 5 0.06 — 20F Bedrooms/Living Rooms 5 0.06 — 10F Office Spaces 5 0.06 — 5 Conference Rooms 5 0.06 — 50 Multipurpose Assembly Spaces 5 0.06 — 120F Reception Areas 5 0.06 — 30 Break RoomsF 5F 0.12F — 50F Central Laundry RoomsF,G 5 (7.5)F,G 0.12 (0.06)F,G — 10 (20)F,G Occupiable Dry Storage RoomsF 5F 0.06F — 2F Unoccupiable Storage RoomsH — 0.12H — — Lobbies/Prefunction Spaces 7.5 0.06 — 30F Library 5 0.12 — 10 Lecture Classrooms 7.5 0.06 — 65 Computer Labs 10 0.12 — 25 Dining Rooms 7.5 0.18 — 70 Central KitchensF 7.5F 0.12F 0.7 cfm/ft2 C,F 20F Barber Shops 7.5 0.06 0.5 cfm/ft2 C 25 Beauty and Nail Salons 20 0.12 0.6 cfm/ft2 C 25 Public Bathrooms — — 50 or 70 cfm/toilet and/or urinalI — Private Bathrooms — — 25 or 50 cfmJ,K — Shower RoomsH — — 20 or 50 cfm/shower headH,K — Locker Rooms — — 0.25 cfm/ft2 C — A Requirements published in: Dallas Building Code: Mechanical (CHAPTER 55: 2012 International Mechanical Code with Dallas Amendments), effective November 1, 2013, and American National Standards Institute (ANSI)/ASHRAE Standard 62.1-2013: Ventilation for Acceptable Indoor Air Quality. In most cases, the Dallas Building Code has adopted ventilation recommendations directly from ASHRAE Standard 62.1. B cfm/person = cubic feet per minute (also commonly shown as ft3/min) per person typically in the occupied space C cfm/ft2 = cubic feet per minute (also commonly shown as ft3/min) per square foot of occupied space
Page 32 Health Hazard Evaluation Report 2013-0145-3209

D Mechanical exhaust should be released directly outdoors at least 25 feet away from air intakes. Recirculating exhaust air back into the building should be avoided, but is permissible under some circumstances.E #/1000ft2 = number of people per 1000 square feet of occupied space. These values are typical maximum occupant densities in spaces that are useful for building/HVAC system 

design. If actual occupant densities are known, they should be used instead of these default values. F Requirements are only published in ASHRAE Standard 62.1-2013. No directly corresponding values appear in the Dallas Building Code.

G The Dallas Building Code and ASHRAE Standard 62.1-2013 both include identical recommendations for “coin-operated laundries.” Those values are shown in parentheses. H Requirements are only published in the Dallas Building Code. No directly corresponding values appear in ASHRAE Standard 62.1-2013.I The Dallas Building Code and ASHRAE Standard 62.1-2013 both include the same exhaust recommendations for public bathrooms, but they differ in how the recommendations 

are applied. The Dallas Building Code applies the recommendations based on exhaust fan type. If exhaust fans are operated continuously, the lower rate may be used. If exhaust fans are operated intermittently (e.g., fans activated by a light switch), the higher rate should be used. The ASHRAE Standard 62.1-2013 recommendation is based on expected usage. Provide the higher rate when periods of heavy use are expected to occur (e.g. prior to guests leaving in the morning). If periods of heavy use are not anticipated, the lower rate may be used.

J These rates are for bathrooms intended for use by one person at a time.K If exhaust fans are operated continuously, the lower rate may be used. If exhaust fans are operated intermittently (e.g., fans activated by a light switch), the higher rate should be 

used.
Health Hazard Evaluation Report 2013-0145-3209 Page 33 Table 3. Total air delivered by ventilation systems, occupant densities, and recommended outdoor air and exhaust flow SpaceA AHU Serving Space Supply Air Flow (cfm)B Exhaust Air Flow (cfm)B Approximate Area (ft2)C Typical OccupantsD Occupant Density (#/1000 ft2) D,E,F Recommended Outside Air Flow (cfm)B,G Recommended Exhaust Air Flow (cfm)B,F,G Welcome Building Intake Area W101 AHU-W1 885 600 710 6 8 70 N/AH Main Reception Area W102I AHU-W1 2230 1390 2360 60 25 440 N/AH Office W103 AHU-W1 180 350 125 1 *8 10 N/AH Office W104 AHU-W1 160 350 125 1 *8 10 N/AH Office W105 AHU-W1 160 380 125 1 *8 10 N/AH Security Office W106 AHU-W1 110 375 125 1 *8 10 N/AH Library W107 AHU-W1 535 385 970 15 *15 190 N/AH Women’s Services Day Room W108J AHU-W1 365 340 775 10 13 100 N/AH Women’s Bathroom W110 AHU-W1 300 225 550 6 11 N/AH,K *720 (420)K,L Laundry Room W119 AHU-W1 1095 235 470 4 9 60 (80)M N/AH Personal Care Area W121 AHU-W1 250 150 360 6 17 70 *180 Phone Room W127 AHU-W1 40 80 115 2 17 20 N/AH Men’s Bathroom W130 AHU-W1 290 35 615 8 13 N/AH,K *1140 (840)K,L Dining Building Large Dining Area D100 AHU-D1 3400 0N,O 2500 120 48 1350 N/AH Small Dining Area D115 AHU-D1 2555 1850 890 25 28 350 N/AH Women’s Bathroom Alcove D116 AHU-D1 75 0N 60 1 17 N/AH,K *50 Women’s Bathroom D117 AHU-D1 100 NMFP 40 1 25 N/AH,K *50 Women’s Shower Room D118 AHU-D1 MNTQ MNTQ 70 1 14 N/AH,K *100 (0)K,L Men’s Bathroom Alcove D119 AHU-D1 75 0N 60 1 17 N/AH,K *50 Men’s Bathroom D120 AHU-D1 90 -35R 40 1 25 N/AH,K *50 Men’s Shower Room D121 AHU-D1 80 -80R 70 1 14 N/AH,K *100 (0)K,L Pavilion Sleeping Area Pavilion Area D100 None None None 8655 250 *29 1770 N/AH Outdoor Women’s Bathroom None None None 660 10 15 N/AH,K *790 (490)K,L Outdoor Men’s Bathroom None None None 660 10 15 N/AH,K *1210 (910)K,L
Page 34 Health Hazard Evaluation Report 2013-0145-3209 Table 3 (continued). Total air delivered by ventilation systems, occupant densities, and recommended outdoor air and exhaust flow SpaceA AHU Serving Space Supply Air Flow (cfm)B Exhaust Air Flow (cfm)B Approximate Area (ft2)C Typical OccupantsD Occupant Density (#/1000 ft2) D,E,F Recommended Outside Air Flow (cfm)B,G Recommended Exhaust Air Flow (cfm)B,F,G Services Building – First Floor Main Women’s Bathroom AHU-S1 130 NMFP 200 2 10 N/AH,K *280 Main Men’s Bathroom AHU-S1 70 NMFP 200 2 10 N/AH,K *280 Medical Clinic Waiting Area S125 AHU-S1 720 410 490 10 20 80 N/AH Medical Clinic Admission S124S AHU-S1 360 125 510 1 2 40 N/AH Medical Clinic Exam Room 1 AHU-S1 150 55 110 2 18 N/A (30)H,T N/AH Medical Clinic Exam Room 2 AHU-S1 130 75 110 2 18 N/A (30)H,T N/AH Medical Clinic Exam Room 3 AHU-S1 40 45 110 2 18 N/A (30)H,T N/AH Medical Clinic Exam Room 4 AHU-S1 NMFP 115 110 2 18 N/A (30)H,T N/AH Medical Clinic Exam Room 5 AHU-S1 165 45 110 2 18 N/A (30)H,T N/AH Medical Clinic Exam Room 6 AHU-S1 NMFP NMFP 100 2 20 N/A (30)H,T N/AH Medical Clinic Counseling Office 1 AHU-S1 70 NMFP 60 1 *17 10 N/AH Medical Clinic Counseling Office 2 AHU-S1 50 50 60 1 *17 10 N/AH Medical Clinic Nursing Office AHU-S1 NMFP 220 110 1 *9 10 N/AH Medical Clinic Provider Office S135 AHU-S1 75 40 80 1 *13 10 N/AH Medical Clinic Patient Restroom AHU-S1 NMFP NMFP 60 1 17 N/AH,K *50 Medical Clinic Staff Restroom AHU-S1 NMFP NMFP 60 1 17 N/AH,K *50 Behavioral Clinic Waiting Area S161 AHU-S1 450 115 285 6 21 50 N/AH Behavioral Clinic Admission S160S AHU-S1 110 135 595 1 2 40 N/AH Behavioral Clinic Conference Room S144 AHU-S1 155 275 330 8 24 60 N/AH Behavioral Clinic Office S145 AHU-S1 40 90 110 2 *18 20 N/AH Behavioral Clinic Office S146 AHU-S1 NMFP 30 110 2 *18 20 N/AH Behavioral Clinic Office S147 AHU-S1 40 55 110 2 *18 20 N/AH Behavioral Clinic Office S148 AHU-S1 40 60 110 2 *18 20 N/AH Behavioral Clinic Office S149 AHU-S1 45 70 110 2 *18 20 N/AH
Health Hazard Evaluation Report 2013-0145-3209 Page 35 Table 3 (continued). Total air delivered by ventilation systems, occupant densities, and recommended outdoor air and exhaust flow SpaceA AHU Serving Space Supply Air Flow (cfm)B Exhaust Air Flow (cfm)B Approximate Area (ft2)C Typical OccupantsD Occupant Density (#/1000 ft2) D,E,F Recommended Outside Air Flow (cfm)B,G Recommended Exhaust Air Flow (cfm)B,F,G Services Building – First Floor (continued) Behavioral Clinic Office S150 AHU-S1 45 50 110 2 *18 20 N/AH Behavioral Clinic Office S151 AHU-S1 90 NMFP 110 2 *18 20 N/AH Behavioral Clinic Office S152 AHU-S1 60 NMFP 110 2 *18 20 N/AH Behavioral Clinic Office S153 AHU-S1 70 65 110 2 *18 20 N/AH Behavioral Clinic Office S154 AHU-S1 35 100 110 2 *18 20 N/AH Behavioral Clinic Office S159 AHU-S1 NMFP 0N 110 2 *18 20 N/AH Behavioral Clinic Women’s Bathroom AHU-S1 NMFP NMFP 40 1 25 N/AH,K *50 Behavioral Clinic Men’s Bathroom AHU-S1 60 NMFP 40 1 25 N/AH,K *50 Office S100 AHU-S1 145 125 105 2 *19 20 N/AH Office S101 AHU-S1 140 110 120 2 *17 20 N/AH Office S102 AHU-S1 190 95 120 2 *17 20 N/AH Office S103 AHU-S1 NMFP 110 95 2 *21 20 N/AH Office S104A AHU-S1 NMFP 100 95 2 *21 20 N/AH Office S104 AHU-S1 35 45 95 2 *21 20 N/AH Office S105 AHU-S1 170 100 100 2 *20 20 N/AH Office S106 AHU-S1 205 95 100 2 *20 20 N/AH Classroom S107 AHU-S1 135 175 450 10 22 100 N/AH Executive Staff Meeting Room S108 AHU-S1 1330 475 585 20 34 140 N/AH Computer Training Room S109 AHU-S1 520 455 610 15 25 220 N/AH Classroom S110 AHU-S1 720 290 475 20 42 180 N/AH
Page 36 Health Hazard Evaluation Report 2013-0145-3209 Table 3 (continued). Total air delivered by ventilation systems, occupant densities, and recommended outdoor air and exhaust flow SpaceA AHU Serving Space Supply Air Flow (cfm)B Exhaust Air Flow (cfm)B Approximate Area (ft2)C Typical OccupantsD Occupant Density (#/1000 ft2) D,E,F Recommended Outside Air Flow (cfm)B,G Recommended Exhaust Air Flow (cfm)B,F,G Services Building – Second Floor Women’s North Day Room S221 AHU-S2 NMFP 240 275 3 11 N/A (30)H,U N/AH Women’s North Bathroom S207 and S216 AHU-S2 NMFP 190 275 3 11 N/AH,K *240 (140)K,L Women’s Dorm Room #1 AHU-S2 270 165 155 2 13 20 N/AH Women’s Dorm Room #2 AHU-S2 265 145 145 2 14 20 N/AH Women’s Dorm Room #3 AHU-S2 275 165 145 2 14 20 N/AH Women’s Dorm Room #4 AHU-S2 295 165 145 2 14 20 N/AH Women’s Dorm Room #5 AHU-S2 670 100 190 2 11 20 N/AH Women’s Dorm Room #6 AHU-S2 90 210 170 3 18 30 N/AH Women’s Dorm Room #7 AHU-S2 115 140 170 3 18 30 N/AH Women’s Dorm Room #8 AHU-S2 555 245 165 2 12 20 N/AH Women’s Dorm Room #9 AHU-S2 460 200 150 2 13 20 N/AH Women’s Dorm Room #10 AHU-S2 420 165 150 2 13 20 N/AH Women’s Dorm Room #11 AHU-S2 410 175 150 2 13 20 N/AH Women’s South Bathroom S208 and S215 AHU-S2 NMFP 290 275 3 11 N/AH,K 240 (140)K,L Women’s South Day Room S219 AHU-S2 730 310 295 3 10 N/A (30)H,U N/AH Women’s Central Kitchenette S220 AHU-S2 NMFP 45 290 2 7 N/A (30)H,U N/AH Counseling Office S241 AHU-S2 120 130 110 2 *18 20 N/AH Counseling Office S251 AHU-S2 120 95 110 2 *18 20 N/AH Counseling Office S252 AHU-S2 125 145 110 2 *18 20 N/AH Counseling Office S253 AHU-S2 110 90 110 2 *18 20 N/AH Counseling Office S254 AHU-S2 85 140 110 2 *18 20 N/AH Counseling Office S255 AHU-S2 100 135 110 2 *18 20 N/AH Counseling Office S256 AHU-S2 110 120 110 2 *18 20 N/AH Counseling Office S257 AHU-S2 125 130 110 2 *18 20 N/AH Counseling Office S260 AHU-S2 NMFP 185 110 2 *18 20 N/AH Counseling Office S262 AHU-S2 70 NMFP 110 2 *18 20 N/AH
Health Hazard Evaluation Report 2013-0145-3209 Page 37 Table 3 (continued). Total air delivered by ventilation systems, occupant densities, and recommended outdoor air and exhaust flow SpaceA AHU Serving Space Supply Air Flow (cfm)B Exhaust Air Flow (cfm)B Approximate Area (ft2)C Typical OccupantsD Occupant Density (#/1000 ft2) D,E,F Recommended Outside Air Flow (cfm)B,G Recommended Exhaust Air Flow (cfm)B,F,G Services Building – Third Floor Men’s Housing Unit B AHU-S3 6655 1605 3850 40 10 430 N/AH Unit B Day Room S338 AHU-S3 850 285 465 6 13 N/A (60)H,U N/AH Unit B Bathroom and Shower Room AHU-S3 175 585 350 6 17 N/AH,K 550 (350)K,L Men’s Housing Unit C AHU-S3 3085 1205 2265 22 10 250 N/AH Unit C Day Room S300 AHU-S3 390 135 300 6 20 N/A (50)H,U N/AH Unit C Bathroom and Shower Room AHU-S3 320 415 285 3 11 N/AH,K 240 (140)K,L Handicap Room #1 AHU-S3 180 100 105 2 19 20 N/AH Handicap Room #2 AHU-S3 200 100 105 2 19 20 N/AH Handicap Room #3 AHU-S3 145 90 105 2 19 20 N/AH Handicap Room #4 AHU-S3 135 65 105 2 19 20 N/AH Handicap Room #5 AHU-S3 130 70 105 2 19 20 N/AH Handicap Room #6 AHU-S3 130 50 105 2 19 20 N/AH Handicap Room #7 AHU-S3 185 100 105 2 19 20 N/AH Hallway Outside Handicap Rooms AHU-S3 150 0N 465 0 0 30 N/AH Handicap Bathroom #1 AHU-S3 NMFP 75 55 1 18 N/AH,K *150 (50)K,L Handicap Bathroom #2 AHU-S3 NMFP 75 40 1 25 N/AH,K *100 (50)K,L Handicap Bathroom #3 AHU-S3 NMFP 60 40 1 25 N/AH,K *100 (50)K,L A May not represent all locations served by the AHU. B cfm = cubic feet per minute (also commonly shown as ft3/min). C ft2 = square feet. D Occupant numbers estimated by visual observation during NIOSH visit. E #/1000 ft2 = number of occupants per 1000 ft2 of occupied floor space. Calculated by dividing the number of typical occupants in the space by the approximate area of the space and multiplying by 1000. F Entries preceded by an asterisk (*) represent spaces where the actual occupant density likely exceeds the default occupant density or where the measured exhaust flow rate is lower than the required exhaust flow rate for typical occupancy levels, as shown in Table 2.
Page 38 Health Hazard Evaluation Report 2013-0145-3209

G Calculated based on recommendations published in: Dallas Building Code: Mechanical (CHAPTER 55: 2012 International Mechanical Code with Dallas Amendments), effective 

November 1, 2013, and American National Standards Institute (ANSI)/ASHRAE Standard 62.1-2013: Ventilation for Acceptable Indoor Air Quality. In most cases, the Dallas Building Code has adopted ventilation recommendations directly from ASHRAE Standard 62.1. Values have been rounded to the nearest 10 cfm. H N/A = not applicable. 

I Values presented for the Main Reception Area (W102) include ventilation and physical measurements for Hallway W102 and the adjoining part of hallway W109 to the closed 

door.

J Values presented for the Women’s Services Day Room (W108) exclude the private bathroom in the area.K Neither the Dallas Building Code nor ASHRAE Standard 62.1-2013 include outdoor air recommendations for restrooms, bathrooms, and shower facilities, but they both include 

exhaust recommendations for public bathrooms. The Dallas Building Code applies the recommendations based on exhaust fan type. If exhaust fans are operated continuously, 50 cfm per water closet should be exhausted. If exhaust fans are operated intermittently (e.g., fans activated by a light switch), 70 cfm per water closet should be exhausted. The ASHRAE Standard 62.1-2013 recommendation is based on expected usage. 70 cfm per water closet should be provided when periods of heavy use are expected to occur (e.g. prior to guests leaving in the morning). If periods of heavy use are not anticipated, 50 cfm per water closet is prescribed. For private bathrooms (i.e., bathrooms meant to be occupied by only one person at a time), the Dallas Building Code and ASHRAE Standard 62.1-2013 both specify 50 cfm per water closet if the exhaust fan is operated intermittently and 25 cfm per water closet for continuously operated exhaust fans. For shower facilities, the Dallas Building Code prescribes 20 cfm per shower head if exhaust fans are operated continuously or 50 cfm per shower head if exhaust fans are operated intermittently. ASHRAE Standard 62.1-2013 does not provide exhaust air flows for shower rooms. L The required exhaust flow according to the Dallas Building Code is shown first and the ASHRAE Standard 62.1-2013 requirement is shown in parentheses (assuming no exhaust requirement for the shower heads). M Requirements for central laundry facilities are only published in ASHRAE Standard 62.1-2013. No directly corresponding values appear in the Dallas Building Code. However, the Dallas Building Code and ASHRAE Standard 62.1-2013 both include identical recommendations for “coin-operated laundries.” That value is shown in parentheses. N There were no exhaust grilles in this area.

O All exhaust air from the large dining room was exhausted through exhaust grilles in the kitchen meal service area. These exhaust flows were not measured.P NMF = no measureable flow. The air capture hoods used to determine air flow measurements were unable to accurately read volumetric air flow rates less than 30 cfm. When 

the actual flow is below 30 cfm, the air capture hoods typically read 0 cfm, although the true value could be anywhere between 0 and 30 cfm. Q MNT = measurements not taken. This room was locked.

R The exhaust grilles were actually serving to supply air to the space.S The area and ventilation measurements for this space includes the adjacent hallway.T Neither the Dallas Building Code nor ASHRAE Standard 62.1-2013 include outdoor air recommendations for medical examination rooms. However, ANSI/ASHRAE Standard 

170-2013: Ventilation of Health Care Facilities does address medical examination rooms. In that standard, a ventilation rate of 6 total air changes per hour is recommended for examination rooms with at least 2 air changes per hour of outdoor air. That translates to approximately 30 cfm of outdoor air in each of the six examination rooms in the medical clinic. This number is reflected in parentheses. U These spaces were classified as break rooms. The Dallas Building Code does not provide an outdoor air requirement for these spaces, so that value is shown as “N/A.” The ASHRAE Standard 62.1-2013 requirement is shown in parentheses.
Health Hazard Evaluation Report 2013-0145-3209 Page 39

Figures

Figure 1. Typical upper-air UVGI installations: Left–Wall-mounted fixture with louvers 

installed in a health clinic; Right–Ceiling-mounted fixture with an internal fan 

installed in a homeless shelter.
Page 40 Health Hazard Evaluation Report 2013-0145-3209

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Health Hazard Evaluation Report 2013-0145-3209 Page 41

Keywords: NAICS 624221 (Temporary Shelters), tuberculosis, environmental controls, 

ventilation, homeless shelter, airborne infection, airborne transmission, respiratory
Page 42 Health Hazard Evaluation Report 2013-0145-3209

The Health Hazard Evaluation Program investigates possible health hazards in the workplace 

under the authority of the Occupational Safety and Health Act of 1970 (29 U.S.C. § 669(a)

(6)). The Health Hazard Evaluation Program also provides, upon request, technical assistance 

to federal, state, and local agencies to investigate occupational health hazards and to prevent 

occupational disease or injury. Regulations guiding the Program can be found in Title 42, 

Code of Federal Regulations, Part 85; Requests for Health Hazard Evaluations (42 CPR Part 

85).

Disclaimer 

The recommendations in this report are made on the basis of the findings at the workplace 

evaluated and may not be applicable to other workplaces.

Mention of any company or product in this report does not constitute endorsement by the 

National Institute for Occupational Safety and Health (NIOSH).

Citations to Web sites external to NlOSH do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or products. NIOSH is not responsible for the 

content of these Web sites. All Web addresses referenced in this document were accessible as 

of the publication date.

Acknowledgments

Desktop Publisher: Tia McClelland

Availability of Report

Copies of this report have been sent to representatives from the shelter, DCHHS, the Texas 

Department of State Health Services, CDC/NCHHSTP/DTBE, and the OSHA Regional 

Office. This report is not copyrighted and may be freely reproduced. This report is available 

at http://www.cdc.gov/niosh/hhe/reports/pdfs/2013-0145-3209.pdf.

Recommended citation for this report:

NIOSH [2014]. Health hazard evaluation report: evaluation of 

environmental controls at a homeless shelter associated with a 

tuberculosis outbreak – Texas. By Martin, Jr. SB, Lawrence RB, Mead 

KR. Morgantown, WV: U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, NIOSH HETA No. 2013-0145-3209.
To receive documents or other information about

occupational safety and health topics, contact NIOSH

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

TTY: 1-888-232-6348

email: cdcinfo@cdc.gov

or visit the NIOSH website at http://www.cdc.gov/niosh

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