Health Hazard Evaluation Report 2013-0110-3218 Page 1

Evaluation of Environmental Controls at a 

Faith-Based Homeless Shelter Associated 

with a Tuberculosis Outbreak – Texas

Report No. 2013-0110-3218

August 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 2013-0110-3218

Contents

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

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

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

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

Background.......................................... 2

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

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

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

Recommendations............................. 22

Outline of Future Involvement......... 26

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

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

Figures................................................ 38

Acknowledgements........................... 45

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 2013-0110-3218 Page i

NIOSH investigators 

conducted an assessment of 

environmental controls at a 

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.

Highlights of this Evaluation

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

assistance request from the Executive Director of a large faith-based homeless shelter 

in Dallas, Texas. The request asked NIOSH to assess the heating, ventilation, and airconditioning 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 3-5, 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 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 ranged from newer, well 

maintained systems to old, inoperable systems. 

Ventilation filters were often missing or 

installed in incorrect configurations.

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

in their current configurations.

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

other airborne infectious disease from the general guest population.

● 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.

 
Page ii Health Hazard Evaluation Report 2013-0110-3218

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 written comprehensive infection control plan with input from the Dallas 

County Department of Health and Human Services.

● Repair or replace existing air-handling units, as necessary to ensure all occupied spaces 

of the facility are served by mechanical ventilation.

● Make additional ventilation system changes to ensure all occupied areas of the shelter 

receive outdoor air in amounts that meet Dallas Mechanical Code and ASHRAE 

standards.

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

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

● Create an enclosed, ventilated space at the shelter for use as a respiratory separation 

area.

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

chapel/gymnasium.

● 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 for shelter staff 

and volunteers 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 2013-0110-3218 Page iii

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Page iv Health Hazard Evaluation Report 2013-0110-3218

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 2013-0110-3218 Page 1

Summary

On March 21, 2013, the National Institute for Occupational Safety and Health (NIOSH) 

received a request for technical assistance from the Chief Epidemiologist of the Dallas County 

Department of Health and Human Services, on behalf of the Executive Director of a large 

faith-based homeless shelter in Dallas, Texas, which was one of two shelters linked to an 

ongoing tuberculosis outbreak among homeless people in the Dallas area. 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 air-handling units (AHUs) providing air to the facility, and visually 

inspected the units, when possible. We also measured the air flow rate through all supply 

diffusers and return grilles. 

Over the last two decades, the shelter has acquired all of the pieces of a former commercial 

office building. Thus, the shelter inherited HVAC equipment from various manufacturers. 

We were able to identify ventilation quipment from at least 13 different manufacturers during 

our assessment (see Table 1). Air-handling units ranged from newer, well maintained systems 

to old, inoperable systems. Ventilation filters were often missing or installed in incorrect 

configurations. Certain aspects of the ventilation systems’ operation could potentially 

contribute to airborne disease transmission among shelter guests. Some areas of the shelter 

were not being served by mechanical ventilation during our visit, because various AHUs were 

not functional. Additionally, it appeared the AHUs were not providing adequate outdoor 

air to the occupied spaces, 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 

be served by mechanical ventilation and all areas supplied with adequate amounts of outdoor 

air, as prescribed by the Dallas Mechanical Code and ASHRAE standards. In addition, we 

identified areas, at least one of which 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, 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.
Page 2 Health Hazard Evaluation Report 2013-0110-3218

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, have identified two large 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 the 

faith-based shelter’s heating, ventilation, and air-conditioning (HVAC) systems and make 

recommendations to improve overall environmental controls. DCHHS persuaded the second 

shelter to submit a request for technical assistance to DRDS/NIOSH/CDC 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 first homeless shelter. It details and prioritizes our recommendations 

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
Health Hazard Evaluation Report 2013-0110-3218 Page 3

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 shelter is a faith-based provider of food, beds and clothing to the homeless men, women 

and children in Dallas County, TX. The men’s shelter and administrative offices opened at 

its current location in the outskirts of Dallas, TX, in 1993. It is for men only and is the oldest 

homeless service provider in Dallas. It has a daily census of approximately 335 people, and 

has been at capacity every night since 2008. Women and children are referred to the other 

branches of the shelter. Homeless services are provided to over 4,000 men, women and 

children per year. 

Our site visit included only the men’s shelter, which moved into what was an existing twostory commercial office building. A one-million dollar donation made the move possible 

from the shelter’s former location in downtown Dallas. Since the building consisted of several 

smaller offices and shops, renovations were necessary to transform the space into areas useful 

for a homeless shelter. The renovations began almost immediately, and continue to this day. 

The shelter recently purchased more “storefront space” and created a dorm with 68 additional 

beds in March 2013. There is a current renovation project for an additional 130 beds in 

development. After that addition is complete, the entire facility will have 465 beds. The 

renovations have primarily been to the inside physical layout of the building with walls being 

torn down or erected to create useful space for the shelter’s many programs. The piecemeal 

nature of the ventilation systems remains virtually untouched by the renovations, with many 

small areas (e.g., a former office or shop) still being served by its own air handling unit(s). 

However, the shelter has installed some new ventilation systems to occupied spaces that 

replace multiple older units that still exist on the roof and are intentionally no longer used.

Daily intake of overnight clients staying at the men’s shelter is processed through another of 

Dallas’ homeless services providers, and takes place between 4:30-6:30 p.m. daily, seven days 

a week (new clients need to be in line by 4:00 p.m.). As part of the intake process, a client 

is assigned a particular bed at the men’s shelter we visited or another area shelter. Clients 

receiving a bed at the men’s shelter are bussed to the shelter during the late afternoon to early 

evening and bussed back to the intake processing facility the following morning. Any client 

receiving a bed at the men’s shelter is guaranteed that same bed as long as he continues to 

show up each night. Once onsite, overnight clients relinquish clothing, shower, and are issued 

temporary clothes for the night. The facility has secure lockers, where clients are allowed 

to store any personal possessions. Clients sleep in bunk beds in three large dormitory-style 

rooms with varying ceiling heights up to 9-foot ceilings. During periods of bad weather or 
Page 4 Health Hazard Evaluation Report 2013-0110-3218

increased need, the shelter provides additional clients with sleeping bags and houses them in a 

large, open room used as a gymnasium and chapel area.

Aside from overnight clients, other guests live at the shelter and are enrolled in long-term 

programs. A long-term faith-based program is designed to increase the clients’ spirituality 

and teach the skills necessary to reintegrate into society and live an independent life. The 

program is self-paced, and usually takes between eighteen months and two years to complete. 

Clients in the initial stages of the program have their own dormitory area on the second 

floor of the facility. Clients that are fully-committed to the program have their own separate 

dormitory area, also on the second floor of the facility. The shelter also supports homeless 

veterans through the Veterans Administration (VA) per diem program. These veterans stay 

in two separate, second-floor dormitory areas. Through this program, administered by the 

Dallas VA, veterans who are “formerly homeless or in danger of becoming homeless” are 

sent to the shelter to live in a transitional living environment for up to two years. The shelter 

is approved to have up to 40 veterans in the program at any one time. Since the program’s 

inception, there have been between 34-40 veterans living at the shelter at all times.

The first-floor of the shelter is equipped with a fully-functional commercial kitchen and 

dining area. Dinner is served to all overnight guests, along with breakfast the following 

morning. Clients enrolled in the faith-based program and veterans get additional meals. 

The facility’s lock-out hours are from 7:30 p.m. to 8:30 a.m. the following morning. Clients 

enrolled in the faith-based program and veterans are permitted to be inside the shelter at any 

time, but the shelter is mostly empty during the day. 

Since March 2010, the shelter has had an onsite health clinic operated by the Department of 

Family and Community Medicine at the University of Texas Southwestern Medical Center. 

The clinic is free and open to clients on Tuesdays and Thursdays of every week. Physician’s 

Assistants and interns staff the clinic, but no medication is dispensed from the facility. When 

the clinic is open, clients suspected of having respiratory disease are referred to Parkland 

Hospital for medical testing. Engineered infection control measures are minimal for airborne 

infection control.

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 shelter on Monday, June 3, 2013, soon after the opening meeting was 

completed. We were met by the facilities manager and members of the facilities staff, 
Health Hazard Evaluation Report 2013-0110-3218 Page 5

who briefly showed us around the facility and gave us an overview of typical client flow 

and the services provided. At the conclusion of the tour, we began taking physical and 

ventilation measurements in all key areas of the facility, focusing on areas where clients 

typically congregate or spend significant amounts of time. The dining areas, main reception 

areas, dormitories, and day rooms were the areas of primary concern. However, we took 

measurements throughout the building.

We visually inspected all of the rooftop air-handling units (AHUs) and recorded the make 

and model number, when possible. We were unable to inspect AHUs mounted above the 

drop ceilings during our visit. When possible, we measured the air flow rate through supply 

diffusers and return grilles using either a TSI Incorporated (Shoreview, Minnesota) Model 

EBT731 Alnor 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 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 around midday on Wednesday, June 

5, 2013. Before leaving the facility, we met briefly with the Executive Director 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 
Page 6 Health Hazard Evaluation Report 2013-0110-3218

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 

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 shelter administrators, we learned that 

skin tests and chest x-rays for TB were conducted at the shelter quarterly in conjunction 

with DCHHS prior to the outbreak (the testing is done every 60 days since the outbreak). 

Otherwise, it was apparent that limited TB administrative controls were in place at the shelter 

prior to the current disease outbreak. 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 were adopted 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 should 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 active and robust administrative controls in 

place. As with most homeless facilities, the men’s 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 various dormitory-style sleeping areas, the dining areas during meals, and the chapel/

recreation area during periods of high occupancy. Even the best ventilation systems are 

incapable of preventing the spread of infectious disease between clients close to one another. 

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 first step, the development 

of a written comprehensive TB Infection Control Plan (ICP) for the shelter should be 

considered. The administrative controls program would be just one part of the overall ICP. 

At the time of the NIOSH investigation, no such ICP was reported to exist. Information 

on creating detailed ICPs and TB ICP templates for 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 shelter administrators and DCHHS. However, the process should be formally 

documented in a protocol or checklist format. This ensures that each time there is a TB-
Health Hazard Evaluation Report 2013-0110-3218 Page 7

related incident, all necessary agencies understand their responsibilities and should 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 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 shelter’s AHUs is provided in Table 1. Unfortunately, a 

combination of scheduling conflicts and the lack of availability of the knowledgeable facilities 

manager resulted in our inability to gather all pertinent information for many of the AHUs. 

While the employee that escorted us during our inspection of the rooftop units did his best to 

assist us, we were unable to obtain specific information for all of the above-ceiling HVAC fan 

units associated with each of the 12 condensing-only units mounted on the roof. Since some 

of the older ventilation systems had been intentionally deactivated and their function replaced 

by newer equipment, it was unclear which existing systems should be functional and which 

were no longer necessary. Additionally, many of the rooftop units had labels that were faded 

or missing, so the make and model of the units could not be identified. Since our site visit, 

follow-up attempts to obtain the missing information have been unsuccessful.

As mentioned previously, the shelter has acquired various pieces of a former commercial 

office building since 1993. Thus, the shelter inherited HVAC equipment from various 

manufacturers as it expanded into all of the areas of the building. We were able to identify 

ventilation equipment from at least 13 different manufacturers during our assessment (see 

Table 1). The age of the equipment ranged from around 5 years to systems that were at least 

two decades old. Cooling to the shelter is provided by direct-expansion air conditioning with 

equipment using one or more refrigerants. Heating is predominantly, if not entirely, provided 

by natural gas. 

We were unable to identify any outdoor air intakes on the perimeter of the building that could 

be attached to the above-ceiling HVAC fan units we were unable to inspect. So, it is unlikely 

those units were providing any outdoor air to the occupied spaces. Most of the AHUs on 

the rooftop were also configured so that no outdoor air was being supplied to the occupied 

spaces they served, either because the outdoor air dampers were sealed closed or no outdoor 

air dampers existed. However, some of the systems on the roof were providing some outdoor 

air to the facility when they were operational. AHUs 1-B, 7, 29, 31, and 32 did have outdoor 

air dampers that were at least partially open so that fresh air was being provided to the spaces 

they serve (see Table 1). 
Page 8 Health Hazard Evaluation Report 2013-0110-3218

Filtration

The ventilation filters used at the shelter consisted of a combination of disposable filters 

from various manufacturers (see Table 1). While most of the filters were either Glasfloss 

Z-Line (ZL) filters (Glasfloss Industries, Dallas, TX) or Flanders Pre-Pleat 40 filters (Flanders 

Corporation, Washington, NC), there were AAF StrataDensity filters (American Air Filter 

International, Louisville, KY) and other unidentifiable filters being used as well. In some 

cases, the filters installed inside the AHUs were appropriately sized and fit tightly within 

the filter rack. However, there were multiple instances of the filters being either improperly 

sized, loose in the filter rack, or both. For instance, Figure 1 shows a large gap between 

filters installed inside AHU 12 serving offices on the second floor. Figure 2 shows the filters 

installed inside AHU 19 serving the Full Program dormitory on the second floor. Here, 

it is clear that improperly sized filters were forced into the AHU. In both cases, there was 

likely significant filter bypass (air passing between the filters instead of through the filters), 

which should be eliminated to the extent possible. All AHUs should be equipped with a 

configuration of filters that matches that prescribed by the AHU manufacturer. If a proper 

filter configuration still exhibits gaps between the filters, gasketed blanks can be inserted into 

the ends of the filter racks to better seal the filters to one another and the sides of the AHU, 

which will eliminate bypass.

In addition to the ventilation filters in the AHUs, several return grilles on the second floor of 

the building had ventilation filters installed behind them. As an example, Figure 3 shows a 

Glasfloss Z-line filter installed behind a return grille in the Initial Program dormitory area. 

Many other return grilles on the second floor, particularly in the library and lounge area, had 

True Blue Filters (True Blue Company, Laporte, IN) behind them as well. While these filters 

likely provided some filtration, it was unclear whether these filters were used as replacements 

for filters in AHUs or in conjunction with AHU filters. If the filters behind return air grilles 

were meant as replacements for AHU filters, the deviation from intended design provides 

ample opportunity for filter bypass and air to be pulled into the AHU in the space between 

the return grilles and the AHU itself. 

The Glasfloss Z Line and Flanders Pre-Pleat 40 disposable panel filters both 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 not rated against particles 

in the 1.0–3.0 μm size range, which includes droplet nuclei responsible for M. tuberculosis

transmission [ANSI/ASHRAE 2012]. The AAF StrataDensity filters have a reported MERV 

of 4, which provides a filtration efficiency of less than 20% against 3.0 to 10.0 μm particles and 

are unrated for particles in the 1.0–3.0 μm size range [ANSI/ASHRAE 2012]. The True Blue 

filters have a reported MERV of 7, so their filtration efficiency would fall somewhere between 

that reported for MERV 4 and MERV 8 filters. The filtration efficiencies for the unidentified 

filters are unknown. 
Health Hazard Evaluation Report 2013-0110-3218 Page 9

When part of an 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. Selecting filters from only one manufacturer 

that provides all the necessary sizes might also help alleviate confusion during filter changes 

and save money on bulk filter purchases. 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.

Preventive Maintenance

The ventilation system preventive maintenance program at the shelter was coordinated by 

the facilities manager. The AHUs that we could visually assess ranged from newer, wellmaintained units to older units in various states of disrepair. There were also at least three 

rooftop units serving a portion of the second floor Client A Sleeping Area (AHU 6), the 

second floor library (AHU 15), and a portion of the first floor learning center (specific 

AHU unclear), that were reported to be nonfunctional. It was not clear whether this was 

due to equipment failure or intentional deactivation. Filter changes and other typical AHU 

maintenance tasks are addressed by facility staff employed by the shelter. Outside ventilation 

contractors are also brought in when necessary. Overall, the HVAC preventive maintenance 

program was generally effective (i.e., most systems were operational), 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 
Page 10 Health Hazard Evaluation Report 2013-0110-3218

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 published guidelines applicable 

to the shelter. 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 of the shelter 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 

overnight client dormitory areas and the Initial Program dormitory area show high occupant 

densities because many people actually sleep in close proximity to one another in these 

spaces. On the other hand, several of the offices throughout the facility also show high 

occupant densities. Much of this is because the offices are smaller than what is considered 

typical. For private offices, a high occupant density 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, only some 

of the AHUs at the shelter were even capable of introducing outdoor air into the occupied 

spaces they served, and many of those had the outdoor air dampers closed. 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 

was anticipated to be below that prescribed by the Dallas Mechanical Code and ASHRAE.
Health Hazard Evaluation Report 2013-0110-3218 Page 11

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. To supply appropriate levels 

of outdoor air, it is essential that all occupied spaces of the shelter are mechanically ventilated. 

This would require repairing existing equipment that is in disrepair or totally nonfunctional. 

Otherwise, new AHUs should be purchased to replace the damaged and inoperable AHUs. 

It is unlikely that the capacity to introduce and temper (i.e., heat or cool and dehumidify) 

appropriate amounts of outdoor air exists with every AHU in their current state, particularly 

given the heat and humidity typical of Dallas summers. Regardless, each AHU should be 

assessed to determine if adequate capacity does exist to temper the recommended amounts of 

outdoor air under all periods of occupancy and all weather conditions. If so, after repairing 

and replacing AHUs as necessary, opening existing outdoor air intakes and installing new 

intakes where none exist may be all that is necessary to meet required outdoor air levels. 

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 additional 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 outdoor 

air intakes, new cooling and heating coils, 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 

expenses 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 a dedicated 

outdoor air system. This would involve installing at least one new AHU, with ductwork 

extending to all occupied spaces and dedicated specifically for supplying outdoor air. This 

new AHU should be sized to provide adequate outdoor air flow for the entire building 

(approximately 5000 cfm) while also providing the entire capacity to temper and dehumidify 

this outdoor air. The new AHU should provide tempered and dehumidified (supercooled 

to 45–50°F dew point) outdoor air to each space (or existing AHU) in quantities necessary 
Page 12 Health Hazard Evaluation Report 2013-0110-3218

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 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 example, two smaller dedicated outdoor air systems could be used to 

provide outdoor air to individual floors of the building. Regardless of how it is accomplished, 

the primary advantage of the dedicated outdoor air system is that it would not require major 

modifications to the existing AHUs (aside from repairing systems in need of repair and 

replacing inactive ones), 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 system is designed properly, all of the heating and cooling loads for the required outdoor 

air could be transferred to the new AHU(s). This would allow the outdoor air intakes in the 

existing AHUs to be closed permanently. Depending on the available capacity in the existing 

AHUs, the dedicated outdoor air system approach may require more capital expense and 

more renovations for the required ductwork than the first option, but it 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 occupied spaces at the shelter. At the same 

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

guests and staff from the potential of airborne disease transmission. The air flow pattern 

is important in any occupied space, but it is particularly important in areas where clients 

congregate, and especially in the overnight client sleeping areas. The overnight guests are not 

integrated into shelter programs so their backgrounds and medical status may be unknown. 

While even the best ventilation system cannot guarantee preventing disease transmission 

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

reduce the overall transmission potential among guests in each sleeping area. A qualified 

HVAC/ventilation engineer should be consulted for the design of air flow schemes that will 

provide adequate ventilation to room occupants while minimizing the potential for disease 

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

We noticed another issue affecting air flow patterns in other occupied spaces as well. Shortcircuiting of air is a concern in some areas. An extreme example is shown in Figure 4, where 

a supply vent and return grille are directly next to one another in the second floor lounge 

area. The close proximity of the supply to the return can easily result in short-circuiting of 

air, where supply air is immediately pulled into a return grille without providing any useful 

ventilation to room occupants. Many other areas of the shelter had similar configurations, 

although not as extreme. Regardless, to alleviate this concern, the distance between the 

supply vent and return grille should be maximized to the extent possible and supply air 

discharge directed in such a manner to inhibit short-circuiting.

We observed 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. 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 
Health Hazard Evaluation Report 2013-0110-3218 Page 13

where the measured exhaust flow rates were less than the recommended rate as presented in 

Table 2. 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 of the facility 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 

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. Nevertheless, we recommend maintaining the indoor temperature 

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

environment to clients and employees at the shelter. 

 
Page 14 Health Hazard Evaluation Report 2013-0110-3218

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 

enrolled in shelter programs, the background and medical status may be largely unknown for 

guests seeking shelter in the Overnight Client Dormitory areas. Given this fact, we strongly 

recommend creating an area inside the facility 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 traditional client 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 

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. 
Health Hazard Evaluation Report 2013-0110-3218 Page 15

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 overnight dormitories house all overnight guests in the large, open sleeping areas, 

ideally a small room, complete with its own solid ceiling, should be constructed in one 

corner of one of the dormitory rooms 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 new 

room to the AHU serving that space (if necessary). An exhaust fan should be chosen that 

is capable of maintaining the room under negative pressure relative to the adjacent, larger 

sleeping area at all times, with minimal noise. The fan could be mounted directly through 

the wall of the building or on the roof with ductwork running through the wall and up to the 

fan 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 into the shelter for overnight shelter while presenting symptoms of 

respiratory disease, they could 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.

If construction of a separate room inside one of the overnight dormitory rooms is impractical, 

an alternative (but less-desirable) approach is to install impervious retractable partitions 

(e.g. accordion-type room dividers) that could be used to enclose a corner of the sleeping 

area when respiratory separation is warranted. Another area in the shelter that could be 

considered for this purpose is the weight room and/or small area off the chapel/gymnasium. 

These spaces already had retractable partitions that could be used to separate them from the 

larger space. Additionally, this area is well away from the overnight guest population during 

normal operations. Regardless, the partitions should touch the floor and extend as close to 

the ceiling 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, a larger fan would likely be required to maintain negative pressure over that required 

for a solid room.

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 
Page 16 Health Hazard Evaluation Report 2013-0110-3218

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. 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 step-by-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.

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 

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]. 
Health Hazard Evaluation Report 2013-0110-3218 Page 17

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].

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

to clients in key locations within the shelter. In congregate settings typical in homeless 

shelters and healthcare facilities, upper-air UVGI systems (often called upper-room systems) 

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

occupied spaces themselves. Upper-air UV lamp fixtures are suspended from the ceiling 

and/or mounted on walls at a minimum height of 7 feet above the floor (Figure 5) [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-air lamp fixtures utilize small fans to enhance air mixing 

(right photograph in Figure 5) [First et al. 1999a,b; CDC 2005b; NIOSH 2009; ASHRAE 2011, 

2012]. The overall effectiveness of upper-air 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-air 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 
Page 18 Health Hazard Evaluation Report 2013-0110-3218

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-air 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-air UVGI guidelines, to design and install an upper-air UVGI 

system in the chapel/gymnasium area. The high 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 and prevent unnecessary 

UV exposures to people using the stairs to the second floor in the area. The existing 

ventilation systems will also provide air mixing within the entire space that is critical for 

optimum upper-air UVGI system performance. Other areas where upper-air UVGI should be 

considered are all dormitory sleeping areas and the dining room. However, unlike the chapel/

gymnasium, these spaces have shorter ceiling heights, so decisions on fixture selection and 

placement would be more critical. 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 respective areas. It is preferable to operate the system 

24 hours a day every day. As with any environmental control system, the new upper-air 

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 
Health Hazard Evaluation Report 2013-0110-3218 Page 19

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 chapel/gymnasium 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-air UVGI system design, 

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 
Page 20 Health Hazard Evaluation Report 2013-0110-3218

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/TrainingPrevention/Programs/Respiratory.asp.

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. 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.

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 facility was clean and well maintained. However, from an environmental control 

perspective, the gradual inheritance of dozens of AHUs from various manufacturers has 

resulted in some nonfunctional or ineffective ventilation equipment. The HVAC preventive 

maintenance program in place at the shelter is managed by the current facilities manager and 

his maintenance staff. While the results were generally effective given the complexities they 

must deal with, developing a written preventive maintenance or O&M plan for the shelter’s 

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

members change. 

Most of the ventilation systems are not capable of providing outdoor air to the occupied 

spaces in their current configurations. Among those systems with outdoor air capability, most 

of them had their outdoor air dampers sealed closed during our visit. For those few units 

with outdoor air dampers at least partially open, we were unable to accurately determine the 

amount of outdoor air being introduced by each AHU, but the amount was anticipated to be 

less than that required by the Dallas Mechanical Code and ASHRAE guidelines. Given the 
Health Hazard Evaluation Report 2013-0110-3218 Page 21

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. This will require repairing or replacing current 

ventilation systems that do not work or fail to work as necessary. Then, with renovations, 

the other existing AHUs might be made to provide the necessary outdoor air. If not, they 

could be augmented with the installation of a new, dedicated outdoor air system to provide 

the necessary outdoor air. A knowledgeable HVAC engineer should be consulted to discuss 

options for introducing outdoor air throughout the shelter. At the same time, consideration 

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

within the building. 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.

The shelter did not have an area set aside 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 overnight dormitory or 

in the chapel/gymnasium 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. 

Given that the chapel/gymnasium is used for large client gatherings and has a high ceiling, 

a complete upper-air 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 all dormitory areas and the dining room. 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 significant 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 
Page 22 Health Hazard Evaluation Report 2013-0110-3218

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 will 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.

•	 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, including skin tests and chest x-rays 

offered every 60 days and the new TB Card (green card) identification 

process for ensuring every client has been tested for TB prior to 

housing at the shelter, which were implemented after the NIOSH visit.

	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.
Health Hazard Evaluation Report 2013-0110-3218 Page 23

2. Create a respiratory separation area at the shelter.

•	 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 specifically 

for respiratory separation should be constructed in one of the corners along 

an exterior wall inside one of the overnight client dormitories. 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 one 

of the overnight client dormitories when respiratory separation is warranted. 

Another possible area for a separation area with partitions is the weight 

room/meeting room adjacent to the large chapel. Regardless of location, 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 HVAC 

return (if any) from the room or enclosure 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 newlyconstructed 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 2 above).

	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.
Page 24 Health Hazard Evaluation Report 2013-0110-3218

	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 repairs to AHUs requiring maintenance and/or replace 

nonfunctional equipment so all occupied spaces in the shelter are served by a 

mechanical ventilation system. This is the first critical step in improving overall 

environmental controls at the shelter. Once all areas are served by mechanical 

ventilation, improvements to meet outdoor air requirements (see Recommendation #7 

below) can be investigated and final decisions made.

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 

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-air UVGI system in the chapel/gymnasium.

•	 Choose a qualified UVGI fixture manufacturer or system engineer, familiar 

with the NIOSH upper-air 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-air UVGI system all day, every day, or at least at all 

times the area is occupied.
Health Hazard Evaluation Report 2013-0110-3218 Page 25

•	 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 available that can allow adequate outdoor air to be 

supplied to the occupied spaces of the facility. If capacity exists in the current 

AHUs after repairs and replacements are made (see Recommendation #3 

above), the easiest method would be to make necessary adjustments to existing 

outdoor air dampers and install new outdoor air intakes, where necessary, 

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 in areas 

where clients congregate, such as dormitories, the dining room, and the 

chapel/gymnasium. 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.
Page 26 Health Hazard Evaluation Report 2013-0110-3218

•	 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-air UVGI systems.

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 2013-0110-3218 Page 27

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Tables Table 1. General air-handling unit (AHU) information AHU Identifier Main Location Served by AHUA AHU ManufacturerB AHU Model NumberB Brand of Filters Installed in AHUB Actual Filter Configuration in AHUC NotesB

RTU-1 2nd Floor Full Program Dormitory Trane YSC120A3ELA1Z0000000000 Glasfloss Z-Line (4) 20×25×2

RTU-2 2nd Floor Full Program Dormitory Trane YSC120A3ELA1W0000000000 Glasfloss Z-Line (4) 20×25×2

1-B

2nd Floor Locker Room, Shower Area, and Restrooms for Overnight Guests

Carrier 

(Bryant) 580DPV120180AAAA Flanders Pre-Pleat 40 and Glasfloss Z-Line (4) 20×20×2 Some Outdoor Air

2 Condenser Only3 York Condenser Only4 York Condenser Only6 2nd Floor Client A Sleeping Area Not Functional7 2nd Floor Client A and B Sleeping Areas Carrier 580DPV150220AAAA Flanders Pre-Pleat 40 (4) 20×20×2 Some Outdoor Air

New #1 1st Floor Seniors’ Sleeping Area (West Side) York ZS-10N18ATAAA5A Could Not Get Inside – Probably Same as New #3 Filters in return grilles as wellNew #2 1st Floor Seniors’ Locker Room, Entryway, Restroom and Showers Coleman TCJD6054153A Condenser OnlyNew #3 1st Floor Senior Citizens’ Sleeping Area (East Side) York ZS-10N18ATAAA5A American Air Filter (4) 20×24×2New #4 2nd Floor Chaplain’s Office off Game Room Goodman GSC130483BB Condenser Only
Health Hazard Evaluation Report 2013-0110-3218 Page 31 Table 1 (continued). General air-handling unit (AHU) information AHU Identifier Main Location Served by AHUA AHU ManufacturerB AHU Model NumberB Brand of Filters Installed in AHUB Actual Filter Configuration in AHUC NotesB 11 Flanders Pre-Pleat 40 (2) 14×25×1 12 2nd Floor Rooms 223-232 Carrier 580DPV150220AAAA Flanders Pre-Pleat 40 (4) 20×20×2 13 Clothing Office York H1DB036506A Condenser Only 14 Trane BTD748A100B0 Condenser Only 15 2nd Floor Library Climate Control Flanders Pre-Pleat 40 (2) 14×25×1 Not Functional 16 Carrier (Day & Night) 590ANK024000AAAA Condenser Only 17 2nd Floor Game Room Carrier None None Filters in return grilles 18 Chapel Area Carrier (Bryant) 580DPV120180AAAA Flanders Pre-Pleat 40 (4) 20×20×2 19 2nd Floor Full Program Dormitory Glasfloss Z-Line (2) 20×25×1 20 2nd Floor Hallway, Stairwell, and Initial Program Restroom Climate Control None None 21 Snyder General 3WA0368 None None 22 Payne None None 23 1st Floor Learning Center and/or Dining Room Carrier (Bryant) 580DPV120180AAAA Glasfloss Z-Line (4) 20×20×2
Page 32 Health Hazard Evaluation Report 2013-0110-3218 Table 1 (continued). General air-handling unit (AHU) information AHU Identifier Main Location Served by AHUA AHU ManufacturerB AHU Model NumberB Brand of Filters Installed in AHUB Actual Filter Configuration in AHUC NotesB 24 1st Floor Kitchen Carrier (Bryant) 580DPV090125AAAA Flanders Pre-Pleat 40 (4) 20×20×2 25 2nd Floor Director’s Conference Room Frigidaire None None 26 Chapel Area Carrier (Bryant) 580DPV120180AAAA Flanders Pre-Pleat 40 (4) 20×20×2 27 1st Floor Rooms 102-111 Ruud UKKA-A060CK10E Glasfloss Z-Line (2) 16×25×1 28 2nd Floor Director’s Office Carrier (Bryant) 580DPV090125AAAA Flanders Pre-Pleat 40 (4) 16×20×2 29 2nd Floor Rooms 204-210 Glasfloss Z-Line and Clarcor (1) 20×25×1 & (1) 14×25×2 Some Outdoor Air 30 1st Floor Learning Center Carrier (Bryant) 580JP05A072A2A0AAA American Air Filter (2) 16×25×2 31 2nd Floor Chaplain Offices Carrier (Bryant) 580DPV090125AAAA Flanders Pre-Pleat 40 (4) 16×20×2 Some Outdoor Air 32 2nd Floor Hallway Carrier (Bryant) 580DPV036074AAAA Glasfloss Z-Line (2) 16×25×2 Some Outdoor Air 33 Rheem Condenser Only 3435 Goodman CK60-1 Condenser Only 36 Goodman CK30-1A Condenser Only 37 2nd Floor Full Program Dormitory Janitrol Condenser Only A Based on reported information from facility staff during the NIOSH visit. May or may not be entirely correct.

B Information collected during visual inspection of AHU, when possible.C Value in parenthesis represents the number of filters; dimensions are width × height × depth in units of inches.
Health Hazard Evaluation Report 2013-0110-3218 Page 33 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 (CONTINUED ON NEXT PAGE)
Page 34 Health Hazard Evaluation Report 2013-0110-3218 Table 2 Footnotes continued:

C cfm/ft2 = cubic feet per minute (also commonly shown as ft3/min) per square foot of occupied space 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 2013-0110-3218 Page 35 Table 3. Total air delivered by ventilation systems, occupant densities, and recommended outdoor air and exhaust flow SpaceA 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 Chapel/Recreation Facility Chapel/Recreation Area 6120 4470 2955 30 10 330 N/AH First Floor Main Entrance/Lobby 2240 1860 1410 4 3 110 N/AH Game Room/Clinic Waiting Area 1345 NMFI 1670 5 3 130 N/AH Dining Area 5120 2025 1995 8 4 420 N/AH Barber Room 155 0I 195 2 10 30 *100 Senior Sleeping Area 3860 3865 4235 64 15 570 N/AH Senior Locker Room 440 750 610 30 49 N/AH,J 150J Senior Shower/Bathroom 530 0I 460 15 33 N/AH,J *1160 (560)J,K Intake Administrator Office (#128) 735 0I 180 2 *11 20 N/AH Intake Assistant Office #1 (#134) 140 0I 210 1 5 20 N/AH Intake Assistant Office #2 (#127) 180 0I 175 2 *11 20 N/AH Computer Training Room 525 830 675 12 18 200 N/AH Computer Room Bathroom NMFI 35 55 1 18 N/AH,J *50J Overnight Client Dormitory A 1375 1200 2980 102 *34 690 N/AH Overnight Client Dormitory B 1710 1250 1690 62 *37 410 N/AH Overnight Client Dormitory C 1185 925 1425 58 *41 380 N/AH Overnight Client Bathroom 290 NMFI 280 10 36 N/AH,J *1050J Overnight Client Sink Room 290 0I 300 8 27 N/AH,J N/AH,J Overnight Client Shower Room 0I NMFI 405 20 49 N/AH,J *400 (N/A)H,J,K Overnight “Cage” Storage Area 105 0I 70 2 29 10 N/AH Overnight Client Locker Room 1500 850 810 80 99 N/AH 200 Security Room 295 NMFI 180 1 *6 20 N/AH Veterans South Dormitory 770 580 825 16 19 130 N/AH Veterans North Dormitory 1150 1315 1200 24 20 190 N/AH
Page 36 Health Hazard Evaluation Report 2013-0110-3218 Table 3 (continued). Total air delivered by ventilation systems, occupant densities, and recommended outdoor air and exhaust flow SpaceA 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 Second Floor (continued) Eugene Ford Library 805 670 700 6 9 110 N/AH Initial Program Dormitory 1115 185 480 20 *42 130 N/AH Initial Program Bathroom 210 NMFI 110 3 27 N/AH,J *210J Initial Program Shower Room 0I NMFI 160 6 38 N/AH,J 220 (N/A)H,J,K Chaplain’s Office #224 395 620 215 2 *9 20 N/AH Mens Lounge 1300 NMFI 1240 10 8 120 N/AH Chaplain’s Office #217 220 220 180 2 *11 20 N/AH Veterans Affairs Office #216 240 0I 155 2 *13 20 N/AH Waiting Area Outside #216 and #217 365 1430 415 2 5 30 N/AH Chaplain’s Office #213 255 230 225 2 *9 20 N/AH Chaplain’s Office #212 290 0I 185 2 *11 20 N/AH Full Program Library 725 0I 435 3 7 70 N/AH Full Program Dormitory 6385 >5000 3500 46 13 440 N/AH Full Program Bathroom/Shower Room 0I 1085 740 15 20 N/AH,J 960 (560)J,K Director of Development’s Office 150 NMFI 170 1 *6 20 N/AH Chief Administrator’s Office 185 35 170 1 *6 20 N/AH Executive Director’s Waiting Area 195 NMFI 230 3 13 30 N/AH Executive Director’s Boardroom 285 NMFI 375 8 21 60 N/AH Executive Director’s Office 165 NMFI 235 1 4 20 N/AH 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.
Health Hazard Evaluation Report 2013-0110-3218 Page 37 Footnotes for Table 3 Continued: 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 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. If there were no supply vents and/or return grilles in the space, the flow is reported as 0 cfm. J 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 intermit- tently 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. K 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).
Page 38 Health Hazard Evaluation Report 2013-0110-3218

Figures

Figure 1. Filters installed inside AHU 12 at the shelter showing a significant gap 

between individual filters that will allow air to pass between the filters instead of 

through them.
Health Hazard Evaluation Report 2013-0110-3218 Page 39

Figure 2. Incorrect filters installed and subsequently distorted and rendered 

ineffective inside AHU 19 at the shelter.
Page 40 Health Hazard Evaluation Report 2013-0110-3218

Figure 3. Ventilation filter installed directly behind a return air grille in the Initial 

Program Dormitory Area of the shelter.
Health Hazard Evaluation Report 2013-0110-3218 Page 41

Figure 4. Supply vent and return grille directly next to one another in the second 

floor lounge area at the shelter. This configuration will lead to short-circuiting of air 

in the occupied space.
Page 42 Health Hazard Evaluation Report 2013-0110-3218

Figure 5. 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.
Health Hazard Evaluation Report 2013-0110-3218 Page 43

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Page 44 Health Hazard Evaluation Report 2013-0110-3218

Keywords: NAICS 624221 (Temporary Shelters), tuberculosis, environmental controls, 

ventilation, homeless shelter, airborne infection, airborne transmission, respiratory.
Health Hazard Evaluation Report 2013-0110-3218 Page 45

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 invest igate 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. The report may be viewed and 

printed at www.cdc.gov/niosh/hhe/. Copies may be purchased from the National Technical 

Information Service (NTIS) at 5825 Port Royal Road, Springfield, Virginia 22161.

This report is available at http://www.cdc.gov/niosh/hhe/reports/pdfs/2013-0110-3218.pdf.

Recommended citation for this report:

NIOSH [2014]. Health hazard evaluation report: evaluation of 

environmental controls at a faith-based 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. 2013-0110-3218.
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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