Health Hazard Evaluation Report 2012-0265-3183 Page 1

Evaluation of Environmental Controls at a Homeless 

Shelter (Trinity Rescue Mission) Associated with a 

Tuberculosis Outbreak – Florida

Report No. 2012-0265-3183

July 2013

Stephen B. Martin, Jr., MS, PE

Kenneth R. Mead, PhD, PE

R. Brent Lawrence, MS, GSP

Michael C. Beaty

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 2012-0265-3183

Contents

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

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

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

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

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

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

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

Conclusions ................................................... 18

Recommendations ...................................... 19

Outline of Future NIOSH Involvement .... 24

References ..................................................... 26

Tables ............................................................. 29

Figures ........................................................... 35

Acknowledgements .................................... 38

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.
Health Hazard Evaluation Report 2012-0265-3183 Page i

Highlights of this Evaluation

The National Institute for Occupational Safety and Health received a technical assistance request from the Duval County Health Department in Florida. The request asked that we assess 

the heating, ventilation, and air-conditioning systems and make recommendations to improve 

overall environmental controls at Trinity Rescue Mission, a local homeless shelter with epidemiological links to an ongoing tuberculosis outbreak.

What NIOSH Did

● We visited Trinity Rescue Mission on August 23, 2012.

● We met with representatives from the Duval County Health Department to discuss the 

ongoing tuberculosis outbreak.

● We recorded the physical sizes of occupied spaces.

● We measured ventilation air flow into/from occupied spaces.

● We collected information on all shelter air-handling units.

What NIOSH Found

● Trinity Rescue Mission did not have administrative controls in place to identify guests 

on priority screening lists or those with symptoms of tuberculosis.

● The shelter was not working closely with the Duval County Health Department on 

outbreak response efforts. 

● Air-handling units were generally in good working order, but some had improper filter 

configurations and low-efficiency filters.

● No fresh outdoor air was being supplied to the occupied spaces by building mechanical 

systems.

● There were no clearly defined areas to separate guests suspected of having tuberculosis 

from the general guest population.

● Clinic examination rooms in the women’s facility were incorrectly operating under 

positive pressure compared to the adjacent waiting area.

● A written respiratory protection plan did not exist.

● Some bathroom exhaust fans were not functional.

What Trinity Rescue Mission Should Do

● Work in close conjunction with the Duval County Health Department to improve 

overall administrative controls and help ensure rapid identification of guests suspected 

to have tuberculosis.

● Develop and implement a comprehensive infection control plan with input from the 

Duval County Health Department and Florida Department of Health.

● Modify or augment shelter ventilation systems to provide adequate fresh outdoor air to 
Page ii Health Hazard Evaluation Report 2012-0265-3183

all occupied spaces using a strategy compatible with existing system capacities.

● Strategically reposition supply and exhaust grill locations to improve air flow patterns in 

occupied spaces, particularly in the three large guest sleeping areas.

● Install the highest efficiency air filters possible that is consistent with the proper 

operation of each air-handling unit.

● Modify at least one area in each of the men’s and women’s shelters for alternate use as 

respiratory separation areas.

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

men’s barracks-style sleeping area.

● Make ventilation changes to properly maintain medical examination rooms under 

negative pressure relative to the waiting area.

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

requirements of the Occupational Safety and Health Administration’s respiratory 

protection standard 29 Code of Federal Regulations 1910.134.

● Repair or replace all bathroom exhaust fans which are not functioning properly.

● 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 2012-0265-3183 Page iii

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Page iv Health Hazard Evaluation Report 2012-0265-3183

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

DCHD Duval County Health Department

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 2012-0265-3183 Page v

Mention of any company or product does not constitute endorsement by NIOSH. In 

addition, citations to websites external to NIOSH do not constitute NIOSH endorsement 

of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not 

responsible for the content of these websites. All web addresses referenced in this document 
Health Hazard Evaluation Report 2012-0265-3183 Page 1

Summary

In May 2012, the National Institute for Occupational Safety and Health (NIOSH) received a 

request for technical assistance from the Duval County Health Department as part of its response to an ongoing tuberculosis (TB) outbreak among homeless persons in Florida. The request asked NIOSH to assess heating, ventilation, and air-conditioning (HVAC) systems and 

make recommendations to improve overall environmental controls at four homeless facilities 

with epidemiologic links to past or ongoing TB disease transmission.

During an on-site evaluation of the Trinity Rescue Mission homeless shelter in August 2012, 

we collected physical and ventilation measurements in all key areas of the facility. We focused on areas where shelter guests typically 

congregate or spend significant amounts 

of time. We recorded the make and model 

number of all air-handling units (AHUs) 

providing supply air to the facility, and visually inspected the units. When possible, we 

measured the air flow rate through supply 

diffusers and return grilles. 

The ventilation systems in place could have 

contributed to airborne disease transmission 

among shelter guests. With the exception 

of some improper filter configurations and 

the use of inefficient filters in AHUs, the 

units typically used at the shelter appeared 

adequately maintained and were fully operational. Unfortunately, none of the AHUs 

provided fresh outdoor air to the occupied 

spaces, as required by the Florida Building 

Code and the American Society of Heating, Refrigerating and Air-Conditioning 

Engineers design 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, Trinity Rescue Mission reportedly has not made any significant improvements to their administrative controls, particularly when it comes to identifying 

guests showing signs and symptoms of TB. We recommend that Trinity start working closely 

with Duval County Health Department to make improvements to the administrative controls 

at the shelter. From an environmental control standpoint, we suggest that all occupied spaces 

in the shelter are supplied adequate amounts of outdoor air based upon occupancy and room 

use. In addition, areas within the men’s and women’s facilities should be converted for use 

as respiratory separation areas, when necessary. These spaces could serve to separate guests 

NIOSH investigators conducted an assessment of environmental controls in the Trinity 

Rescue Mission, 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.
Page 2 Health Hazard Evaluation Report 2012-0265-3183

suspected of having TB or other respiratory diseases from the remainder of the guest population, until medical evaluation or treatment could be obtained. To provide additional protection to the 104 guests typically housed in the men’s sleeping area, we recommend installing an 

upper-room ultraviolet germicidal irradiation system. We also recommend developing a written infection control plan, HVAC operation and maintenance plan, and a written respiratory 

protection program for the shelter. Having these plans/programs in place will help Trinity 

Rescue Mission under normal operating conditions, and especially during future outbreaks of 

respiratory disease.

Introduction

Since 2004, the Duval County Health Department (DCHD), in conjunction with the Florida 

Department of Health and U.S. Centers for Disease Control and Prevention (CDC), has linked over 

100 cases of active tuberculosis (TB) disease, resulting in 14 deaths, to a cluster having matching 

genotype results (PCR00160 or FL0046) in Duval County, Florida. Roughly half of the cases of active 

TB disease have been identified since 2010. Of the 100 cases, 79% had a history of homelessness, 

incarceration, or substance abuse, with 43% being homeless within one year of diagnosis.

In 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 February and March 2012. In their report 

dated April 5, 2012, the CDC team included a recommendation to improve environmental controls 

at homeless facilities implicated in possible disease transmission. On May 22, 2012, 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 Duval County. The 

request was made by a CDC Public Health Advisor temporarily assigned to Duval County. The 

request specifically asked NIOSH to evaluate shelters’ heating, ventilation, and air-conditioning 

(HVAC) systems and make recommendations to improve overall environmental controls. The request 

was initially made for an assessment at one homeless shelter. However, in subsequent discussions with 

the TB Program Manager at DCHD, a CDC Public Health Advisor with the Florida Department of 

Health, and representatives from CDC/NCHHSTP/DTBE, the request was expanded to include four 

facilities that provide assistance to the homeless and which had epidemiologic links to past or ongoing 

TB disease transmission.

In response to the expanded request, a NIOSH team visited the four facilities in August 2012. This 

report describes the measurements and associated findings from our assessment at the Trinity Rescue 

Mission. It details and prioritizes our recommendations for improving environmental controls at the 

shelter, and outlines the current plan for future NIOSH involvement. 

Keywords: NAICS 624221 (Temporary Shelters), tuberculosis, environmental controls, ventilation, homeless shelter, airborne infection, airborne transmission, respiratory
Health Hazard Evaluation Report 2012-0265-3183 Page 3

Background

Tuberculosis and Homeless Populations 

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

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

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

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

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

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

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

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

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

McAdam et al. 1990; Nolan 1991].

Trinity Rescue Mission 

The Trinity Rescue Mission was established by the congregation of the Trinity Baptist 

Church to provide faith-based programs and services to homeless people in the Jacksonville 

community. The mission is comprised of two shelter facilities that serve the homeless yearround. The men’s facility is a 12,000 square foot, single-story masonry building. Aside from a 

reception area and several staff offices, the building is essentially split in half by a long hallway. 

On one side of the hallway was a kitchen and a large open area used as a dining room and 

assembly space for worship services and shelter meetings. On the other side of the hallway 

is a large barracks-style sleeping area with an attached bathroom and shower room, laundry 

room, and storage areas. A total of 104 beds were available in the men’s sleeping area, with 

22 double bunk beds (44 total beds) located in the center of the room and 20 triple bunk beds 

(60 total beds) constructed along the exterior walls of the space. Four rooftop AHUs serve the 

spaces occupied by guests in the men’s facility.

In 2006, Trinity opened a new 14,000 square foot, two-story brick Women and Children’s 

Center to specifically meet the needs of homeless women and mothers with small children. 

The first floor of the facility houses a reception area, staff offices, conference room, medical 

clinic, dining/education area, nursery, overnight sleeping area, and six dormitory-style 

bedrooms, each with their own bathroom. The women’s overnight sleeping area had nine 

bunk beds (18 total beds) for women requiring an overnight stay. The dormitory- style 

bedrooms were set up for between one and five guests, depending on needs. Three central 

AHUs located in a mechanical room provide ventilation to all occupied spaces on the first 

floor. The second floor of the Women and Children’s Center houses 13 dormitory-style 

bedrooms and two larger barracks-style sleeping areas. All women living on the second floor 

share a large central bathroom and shower room along with a small laundry room. Four 

central AHUs installed in the attic provide ventilation to the occupied spaces on the second 

floor of the facility.

The men’s facility at Trinity is usually at full capacity between men seeking overnight stays and 

those enrolled in the various shelter programs. When necessary, the dining/assembly area can 

be used to house men in excess of the 104 available beds. The Women and Children’s Center 
Page 4 Health Hazard Evaluation Report 2012-0265-3183

had the capacity to house 100 guests or more, but only 50-60 guests reside there on average.

Assessment 

On August 20, 2012, an opening meeting was held at the Duval County Health Department. 

An update was given on the current status of the ongoing TB outbreak among the homeless 

population, and we provided background information on NIOSH, the nature of the technical 

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

Aside from NIOSH and DCHD staff, representatives from three other homeless facilities to 

be visited during the week were in attendance. There was not a representative from Trinity 

Rescue Mission present at the meeting.

We arrived at Trinity Rescue Mission on Thursday, August 23, 2012, and met briefly with 

the Director of Operations. After we unloaded our ventilation equipment, a member of the 

maintenance staff provided a tour of the men’s facility and led us across the parking lot to the 

Women and Children’s Center. While there, staff members provided a tour of both floors, 

and we began taking physical and ventilation measurements in all key areas of the facility. We 

focused on areas where Trinity guests typically congregate or spend significant amounts of 

time.

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

supply air to the two buildings, and we visually inspected all of the units. When possible, 

we measured the air flow rate through supply diffusers and return grilles using a TSI 

Incorporated (Shoreview, Minnesota) Model 8373 Accubalance Plus equipped with air 

capture hood appropriately sized to accommodate each supply diffuser and return grille. The 

Model 8373 measures volumetric air flow rates of 30–2000 cubic feet per minute (cfm) with 

an accuracy of ±5% of the reading and ±5 cfm. The Accubalance Plus is also 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 confirm and visualize the air flow pattern.

After recording our measurements, we intended to meet briefly with the Trinity Director of 

Operations to discuss our general findings. However, he was out of the office and unavailable 

at the time, so a meeting did not occur. A formal closing meeting for our on-site response 

to the technical assistance request for all four facilities was held on August 23, 2012, at the 

DCHD. This meeting provided us an opportunity to discuss our general findings with 

representatives from the Duval County Health Department. There was not a representative 

from Trinity Rescue Mission present at the meeting.
Health Hazard Evaluation Report 2012-0265-3183 Page 5

Results and Discussion

General Tuberculosis Infection Control

All tuberculosis control programs should include three key components: administrative controls (e.g., intake questionnaires and policies), environmental controls (e.g., ventilation and 

filtration), and a respiratory protection program. Ideally, environmental controls and respiratory protection should supplement aggressive administrative controls. Detailed explanations 

for each of these key control elements, as well as a discussion on the hierarchy of their implementation, are outlined in CDC’s Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005 and Prevention and Control of Tuberculosis 

in Correctional and Detention Facilities: Recommendations from CDC [CDC 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

Limited administrative controls for preventing the transmission of airborne diseases were 

in place at the shelter prior to the current disease outbreak. Shelter staff confirmed this fact 

during our visit, and staff members also reported that Trinity had not implemented any new 

administrative procedures or policies in response to the ongoing outbreak. Unlike many 

other homeless facilities in the area, we also learned that Trinity elected not to participate in 

response efforts by DCHD or the Jacksonville Community Tuberculosis Coalition. 

As with most homeless facilities, Trinity frequently provides services to large numbers of 

guests in close proximity to one another. This is particularly the case in the congregate sleeping areas and dining/assembly areas in the men’s and women’s facilities. Even the best ventilation systems are incapable of preventing the spread of disease between guests close to one 

another. Thus, establishing policies and procedures to rapidly identify people with suspected 

disease, keep them separated from the general guest population, and follow up with appropriate medical evaluations and treatment (if necessary) is the most important element in reducing or eliminating the spread of disease. We recommend taking steps to train employees and 

volunteers on symptoms of TB disease and the prevention of TB transmission. Additionally, 

screening procedures should be developed and implemented to help identify guests on target screening lists, or others suspected of having TB. These guests should then be referred to 

DCHD for critical medical testing and care. While enhanced training and detailed administrative policies would help identify guests at risk for disease during the current TB outbreak, 

having new controls in place would reduce the likelihood of airborne disease transmission at 

the shelter in the future as well.

While taking critical steps to enhance the administrative controls at Trinity would be a significant step, the development of a written TB Infection Control Plan (ICP) for the shelter is 

strongly recommended. 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 DCHD and the Florida Department of Health would serve to 
Page 6 Health Hazard Evaluation Report 2012-0265-3183

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. For 

an ICP to be effective, the process should be formally documented in a protocol or checklist 

format. This ensures that each time there is a TB-related incident, all necessary agencies understand their responsibilities and perform their necessary predetermined actions in a consistent manner. Incorporating the input of staff involved in the maintenance and operation of 

facility ventilation systems into the overall infection control program strengthens the program 

and provides these staff members with additional insight as to what ventilation requirements 

are necessary to prevent and/or isolate TB disease. Input from the ventilation staff should be 

sought during the formal creation of the ICP and during subsequent revisions to the plan. 

Environmental Controls

General Ventilation System Information

General information on the AHUs at Trinity, including the areas served by each unit, is provided in Table 1. Of the 11 total AHUs, 10 of the units were produced by Carrier Corporation 

(Farmington, Connecticut). AHU Men-3 was produced by Goodman Manufacturing (Houston, Texas). The four AHUs serving the guest areas of the men’s facility are mounted on the 

roof of the men’s facility. In the women’s facility, three AHUs provide ventilation for the first 

floor of the building. Those units are all located in a large mechanical room on the first floor 

of the Women and Children’s Center. Four additional AHUs are mounted in the attic of the 

women’s facility to provide ventilation to the living areas on the second floor of the building. 

All 11 AHUs supply air to occupied spaces through galvanized steel and flexible fiberglass 

supply ducts. The return air flows back to the units through ducted returns or ceiling plenums. None of the AHUs delivered fresh outdoor air into the buildings.

On the day of our visit, AHU Men-1, AHU Men-2, and AHU Men-4 on the roof of the men’s 

facility were operational and capable of maintaining temperature set points and air flow. It 

was reported that AHU Men-4, serving the men’s kitchen, is rarely used. This was confirmed 

by the cleanliness of the filters inside that unit when compared to filters in the others. During 

our visit, AHU Men-4 was not powered on, so we could not confirm the operational status 

of the unit. The seven AHUs in the Women and Children’s Center were fairly new, and they 

were all operational and capable of maintaining temperature set points and air flow. The mechanical room housing the three AHUs on the first floor of the women’s facility was clean and 

free of clutter, which allowed unfettered access to the three units. The four units in the attic 

were easily accessible via a wooden walkway constructed in the attic space. 

Filtration

As shown in Figure 1, AHU Men-1, AHU Men-2, and AHU Men-4 had ventilation filters that 

appeared to be homemade and not commercially-available. Each of the AHUs had four of the 

homemade filters inside. While the manufacturer prescribes four filters installed in each unit, 

the size of the homemade filters did not match the prescribed filter size. While the homemade filters provided some level of filtration, the level of efficiency was uncertain as the deviation from intended design provided ample opportunity for filter failure and bypass. AHU 

Men-3 contained a set of four properly-sized disposable panel filters from Glasfloss Industries 

(Dallas, Texas). The Glasfloss disposable panel filters do not have a published American Soci-
Health Hazard Evaluation Report 2012-0265-3183 Page 7

ety of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Minimum Efficiency Reporting Value (MERV), which relates to filtration efficiency. However, disposable panel 

filters typically fall into a MERV range of 4 to 6, which corresponds to a removal efficiency of 

up to 50% for 3.0 to 10 micrometer (μm) particles [ANSI/ASHRAE 2007]. However, MERV 

4-6 filters are less than 20% efficient at filtering particles in the 1.0–3.0 μm size range, which 

includes droplet nuclei responsible for M. tuberculosis transmission [ANSI/ASHRAE 2007]. 

All of the ventilation filters used in the Women and Children’s Center were Flanders Corporation (Washington, North Carolina) EZ-Flow disposable panel filters. The EZFlow filters have 

an established ASHRAE MERV of 4, so their efficiency is likely comparable to the disposable 

panel filters described above. 

To prevent the spread of M. tuberculosis, air filters should provide a removal efficiency of 

greater than 90% of particles in the 1.0–3.0 μm size range (corresponding to a MERV 13 or 

higher). During any future HVAC design modifications, system evaluations, or retrofits, the 

selection of filters for use in the AHUs, especially those serving the three main overnight 

sleeping areas, should be closely examined. 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 Trinity was coordinated by shelter 

administrators. With the exception of the homemade and low-efficiency filter issues, all of the 

AHUs were clean and appeared to be adequately maintained. We were unable to determine 

the frequency of ventilation filter replacement. Unfortunately, there is 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. 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 system, is necessary 

in any indoor environment to dilute pollutants that are released by equipment, building 

materials, furnishings, products, and people. In the State of Florida, the 2010 Florida 

Building Code mandates “minimum requirements to safeguard the public health, safety and 

general welfare through structural strength, means of egress facilities, stability, sanitation, 

adequate light and ventilation, energy conservation, and safety to life and property from fire 
Page 8 Health Hazard Evaluation Report 2012-0265-3183

and other hazards attributed to the built environment and to provide safety to fire fighters 

and emergency responders during emergency operations [ICC 2011].” The Florida Building 

Code applies to the “construction, alteration, movement, enlargement, replacement, repair, 

equipment, use and occupancy, location, maintenance, removal and demolition of every 

building or structure or any appurtenances connected or attached to such buildings or 

structures” throughout the state. The Code is based on a variety of model building codes and 

consensus standards from national organizations, which have been modified to fit Florida’s 

specific needs, when necessary. When it comes to ventilation standards, in most cases, the 

Florida Building Code has adopted the recommendations published in American National 

Standards Institute (ANSI)/ASHRAE Standard 62.1-2010: Ventilation for Acceptable Indoor 

Air Quality. These ASHRAE recommendations provide specific details on ventilation for 

acceptable indoor air quality [ANSI/ASHRAE 2010a]. 

The 2010 Florida Building Code and ASHRAE 62.1-2010 recommend outdoor air supply 

rates that take into account people-related contaminant sources as well as building-related 

contaminant sources. Similarly, 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 Trinity. 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 number of occupants per 1000 square 

feet, are provided by the Florida Building 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 physical and ventilation measurements we collected are presented in Table 3. The 

second-to-last column of the table presents the actual occupant densities in each space. 

Values preceded by an asterisk (*) denote areas with occupant densities above typical values 

(i.e., higher than the default values presented in Table 2). High occupant densities are not 

solely indicative of ventilation problems. However, the men’s sleeping area and the women’s 

overnight sleeping room show high occupant densities because many people actually sleep in 

close proximity to one another. Some of the women’s rooms on the first floor of the Women 

and Children’s Center could have high occupant densities when they are filled to their 

reported capacities. 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 disease 

transmission is a concern. 

The last column in Table 3 presents the outdoor air requirements for each space, as established 

by the 2010 Florida Building Code and ASHRAE. As previously noted, none of the AHUs 

at Trinity were delivering any fresh outdoor air into the building. While the rooftop AHUs 

on the men’s facility could easily be modified to bring in outdoor air, the AHUs in the 

women’s facility were not installed in a way that would allow them to easily bring outdoor 

air into the building. Before modifying any of the AHUs to bring in outdoor air, it needs to 

be determined whether each individual AHU has the tempering capacity to incorporate the 
Health Hazard Evaluation Report 2012-0265-3183 Page 9

introduction of outdoor air. If such capacity is available, introducing outdoor air through 

the AHUs would require some modifications and result in increased annual energy costs. 

However, it is important to ensure that all occupied spaces in Trinity are receiving adequate 

amounts of fresh 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. 

Two common approaches could be employed by Trinity to introduce outdoor air into 

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

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

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

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

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

AHU’s conditioning capacity to determine if it can handle the additional tempering and 

dehumidification burden introduced by the outdoor air. Assuming that such conditioning 

capacity exists, modifying the AHUs on the roof of the men’s facility should be made easier by 

the fact that these units are already located outdoors. The system modifications for the AHUs 

in the women’s facility would require more extensive modifications since the required outdoor 

air intakes and dampers would need to be installed into the spaces housing these AHUs. 

Although incorporating outdoor air into the existing AHUs may be the simpler of the two 

solutions and could require the least capital expense, it may cost significantly more in energy 

over time. In their current configurations, the AHUs are simply recirculating air that is 

relatively close to the desired indoor temperature and humidity conditions. After circulating 

through the occupied space, this air requires less conditioning to return it to the desired 

delivery temperature and humidity levels. Once outdoor air is mixed in with the room return 

air, the mixed air stream introduced to each AHU will be further from the desired indoor 

conditions for most of the year. Each AHU will then need to work harder to dehumidify and 

temper the mixed air stream.

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

dedicated outdoor air system. This would involve installing a completely new AHU for the 

men’s facility, with ductwork extending to all occupied spaces of the building. A separate 

dedicated outdoor air system would similarly be required for the women’s facility. For the 

men’s building, the new AHU should be sized to provide adequate outdoor air flow for the 

entire building (approximately 1600 to 1800 cfm) while also providing the entire capacity to 

temper and dehumidify this outdoor air. Similarly, the new AHU for the women’s facility 

would need to provide around 1500 cfm of outdoor air. The new AHUs should provide 

tempered and dehumidified (supercooled to 45–50°F dew point) outdoor air to each space (or 

existing AHU) in quantities necessary to meet Florida Building Code and ASHRAE outdoor 

air requirements. 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 the entire main 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, which would simply continue to recirculate air through 
Page 10 Health Hazard Evaluation Report 2012-0265-3183

the spaces they serve while providing air filtration, heating and cooling. The dedicated 

outdoor air system would certainly 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 the shelters. At the same time, consideration should 

be given to optimizing air flow patterns, particularly in the men’s sleeping area and the 

women’s overnight sleeping room, to reduce the potential of airborne disease transmission 

between guests. While even the best ventilation system cannot guarantee prevention of 

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

patterns could help reduce the overall transmission potential among guests in each sleeping 

area. One way that air flow patterns could be improved in these areas is to supply all air 

(fresh and recirculated) above the center aisles between rows of beds using supply diffusers 

designed to discharge the air in a wide, downward deflected angle. At the same time, return 

grills should be installed along the perimeter of each space. In this arrangement, supply air 

will generally pass over/across each bed and directly back to the AHU. This will reduce the 

potential of exhalations from one person passing through the breathing zone of multiple 

other people sharing the space. This arrangement should also alleviate concerns with shortcircuiting of air, where supply air is immediately pulled into a return grille without providing 

any useful ventilation. Short-circuiting of air is a special concern in the men’s sleeping area 

since all of the supply vents and return grilles are currently located in only one wall of the 

room. Luckily, the 15-feet ceiling height in the men’s sleeping area would allow for easier 

implementation of ventilation improvements than would otherwise be the case. A qualified 

HVAC/ventilation engineer might recommend other air flow schemes that could be similarly 

effective at providing adequate ventilation while minimizing the potential for disease 

transmission. The final chosen design scheme should be qualitatively smoke/fog tested to 

verify performance.

During our visit, we collected measurements in the clinic area on the first floor of the Women 

and Children’s Center and identified two separate examination rooms. Our measurements 

show (see Table 3), and ventilation fog testing confirmed, that exam room #1 and possibly 

exam room #2 (the return grille was obstructed) were improperly maintained under positive 

pressure compared to the adjacent waiting area. Thus, air from inside an exam room migrates 

out of the space into the waiting area. Any areas used for medical evaluations should be 

maintained under negative pressure relative to the surrounding areas, and the pressure 

relationship should be periodically tested and confirmed with a micromanometer or visual 

techniques like smoke tubes or flutter strips. Thus, ventilation changes should be made to 

create a proper air flow pattern that helps keep any airborne infectious agents generated 

inside an exam room from traveling to the adjacent waiting area. The correct negative 

pressure could possibly be established by adjusting existing dampers or ductwork so more 

air is exhausted from the exam rooms than is being supplied to them. Reducing return air 

from adjacent rooms on the same HVAC system will facilitate this approach. If negative 

pressure cannot be maintained with such adjustments, the installation of dedicated exhaust 

fans within each exam room may be required. Depending upon frequency of patient exams, 
Health Hazard Evaluation Report 2012-0265-3183 Page 11

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

negative pressure in these areas, though administrative or occupancy-automated procedures 

to ensure their use during patient exams would be of primary importance.

We also noticed that none of the exhaust fans from bathrooms on the first floor of the 

women’s facility were functioning properly during our visit (see Table 3). 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, 50 cfm of exhaust per toilet/urinal is recommended. For 

private toilets in bathrooms intended to be occupied by only one person at a time, ASHRAE 

62.1-2010 specifies that the exhaust ventilation should be 25 cfm if the exhaust fan is designed 

to operate continuously (the Florida Building Code only requires 20 cfm) or 50 cfm if the 

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

wall switch). The bathroom exhaust fans should be made functional with their exhaust rates 

verified for compliance with the 2010 Florida Building Code, and they should be operational 

any time the bathrooms are occupied. [Note: The kitchen hood exhaust systems 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 55-2010: Thermal 

Environmental Conditions for Human Occupancy specifies conditions in which 80% or 

more of the occupants are expected to find the environment thermally acceptable [ANSI/

ASHRAE 2010b]. Assuming slow air movement and 50% RH, the operative temperatures 

recommended by ASHRAE range from 68.5oF–76oF in the winter, and from 75.5oF–80.5oF 

in the summer (see Table 4). 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%. 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 

because the main guest spaces were generally empty. We recommend maintaining the indoor 

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

comfortable environment to guests at Trinity. Meeting the 30–50% RH recommendation 

would be significantly easier if a dedicated outdoor air system is installed to introduce 

conditioned outdoor air to the shelter, as explained above. 

Respiratory Separation Areas

Currently, Trinity does not have areas set aside for separating guests 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 appropri-
Page 12 Health Hazard Evaluation Report 2012-0265-3183

ate medical evaluations and treatments are initiated is one of the most important elements in 

reducing or eliminating the spread of airborne disease. Since the backgrounds and medical 

statuses may be unknown for overnight guests, we strongly recommend identifying separate 

areas in the men’s and women’s shelters, which can be used for respiratory separation when 

needed. It is important to recognize that respiratory separation is not an alternative to medical evaluation. Rather, it is proposed to be a temporary holding area for guests awaiting transport for medical evaluation. It may also be used to house guests exhibiting signs of respiratory distress without having identified disease. When respiratory separation is not required, 

the areas can be used for normal guest housing or other purposes.

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 any 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 the 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 Trinity would not 

be used to house guests with confirmed disease, so it would not be necessary to meet the strict 

air flow and differential pressure requirements detailed above. However, knowledge of the AII 

design strategies could be useful in designing a respiratory separation area. It is vastly more 

important to establish a negative pressure area that can be used for respiratory separation than 

it is to focus on the respiratory separation area meeting quantitative ventilation requirements.

During our visit, we noticed that rooms 1-6 on the first floor of the women’s facility as areas that could effectively be converted to respiratory separation areas. At least one of these 

small housing rooms should be upgraded to serve this purpose. One or more of these rooms 
Health Hazard Evaluation Report 2012-0265-3183 Page 13

could be converted for respiratory separation by 1) installing a solid, sealed ceiling in place 

of the existing drop ceiling or ensuring the walls for the selected room extend to the hard 

ceiling above the current drop ceiling, 2) installing a new dedicated exhaust fan through the 

outside wall of each selected room to provide the required exhaust air flow when the room 

was in use for respiratory separation, and 3) installing tight-closing dampers (or some other 

mechanism) to completely seal all existing air returns from each selected room (including the 

bathroom) to the AHU serving the room. An exhaust fan should be chosen that is capable of 

maintaining the room under negative pressure relative to the adjacent corridor with minimal 

noise. These fans could be mounted directly in the wall or on the roof with ductwork running 

through the wall and up to the fans on the outside of the shelter. Placement of the fan intakes 

within the room’s private bathroom itself may be required in order to maintain the restroom 

at negative pressure relative to the sleeping area. It is imperative that exhaust air from these 

new fans is directed away from all future AHU air intakes and gathering areas outside the 

shelter.

For the rooms selected for respiratory separation and when respiratory separation is desired, 

the newly installed return air dampers should be sealed to prevent air from inside the room 

returning to the AHU. The new exhaust fan should also be activated to maintain the space 

under negative pressure. For the majority of the time, when respiratory separation is not 

required, the room can be used as normal by deactivating the exhaust fan and reopening the 

return air dampers back to the AHU.

Aside from staff offices, there were no areas identified in the men’s shelter that could readily 

be converted into a space for respiratory separation. Since all men staying at the shelter sleep 

in the same large barracks-style sleeping area, ideally a small room should be constructed in 

a corner of the sleeping area specifically for respiratory separation. Having a separate room 

would allow the space to be used for separation purposes by following the same procedures 

outlined above for spaces in the women’s shelter (except there may not be a return air grille 

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

dividers) that could be used to enclose a corner of the men’s sleeping area when respiratory 

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

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

imperative that exhaust air from this new fan is directed away from all future AHU air intakes 

and gathering areas outside the shelter. 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 in the men’s shelter, 

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

should also be activated to maintain the enclosed space under negative pressure. For the 

majority of the time, when respiratory separation is not required, the corner of the room can 

be used as normal by shutting down the exhaust fan and pushing the retractable partitions out 

of the way.
Page 14 Health Hazard Evaluation Report 2012-0265-3183

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

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

conversion of the spaces from standard housing areas to use for respiratory separation. The 

plan should include contingency plans for moving the guests currently housed in the spaces 

to other locations, steps for cleaning and refurnishing the areas 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 normal guest housing, 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 somewhere 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 any aerosol originating from the patient while simultaneously providing air cleaning to the entire room. NIOSH engineers are available to provide additional 

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

Ultraviolet Germicidal Irradiation 

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

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

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

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

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

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

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

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

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

Although UVC is invisible to the human eye, small amounts of energy released at visible 
Health Hazard Evaluation Report 2012-0265-3183 Page 15

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]. 

In congregate settings typical in homeless shelters and healthcare facilities, upper-room 

UVGI systems (often called upper-air systems) are often used to interrupt the transmission 

of airborne infectious pathogens within the occupied spaces themselves. Upper-room UV 

lamp fixtures are suspended from the ceiling and/or mounted on walls at a minimum height 

of 7 feet above the floor (Figure 2) [Riley and Nardell 1989; Brickner et al. 2003; NIOSH 2009; 

ASHRAE 2011, 2012]. Lamps are shielded to direct radiation upward and outward to create 

an intense zone of UVC in the upper portion of the room while minimizing UVC levels in the 

lower occupied spaces. These fixtures inactivate airborne microorganisms by irradiating them 

as air currents move them into the path of the UV energy. Some upper-room lamp fixtures 

utilize small fans to enhance air mixing (right photograph in Figure 2) [First et al. 1999a,b; 

CDC 2005b; NIOSH 2009; ASHRAE 2011, 2012]. The overall effectiveness of upper-room 

UVGI systems improves significantly when the space is well mixed [Riley and Nardell 1989; 

Brickner et al. 2003]. Although convection air currents created by occupants and equipment 

can provide adequate air circulation in some settings, mechanical ventilation systems and/

or ceiling fans that maximize air mixing are preferable. Floor fans can also be placed in the 

room to ensure adequate mixing.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

targeted for healthcare settings, they are just as applicable to congregate sleeping areas in 
Page 16 Health Hazard Evaluation Report 2012-0265-3183

homeless facilities.

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

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

UVGI system in the men’s sleeping area at Trinity. The 15-feet ceiling height in that space 

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

to create a large irradiance zone in the upper portion of the room. The ability to mount 

the fixtures at higher heights will also help prevent the fixtures from being tampered 

with. The 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 

space, particularly men sleeping or sitting on top bunk beds. If desired, NIOSH engineers 

are available to review any 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-room UVGI system is in place and working properly, the fixtures should 

be operated any time occupants are in the men’s sleeping area. It is preferable to operate 

the system 24 hours per day every day. As with any environmental control system, the new 

upper-room UVGI system will require periodic maintenance. The output from UV lamps 

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

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

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

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

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

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

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

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

accordance with appropriate manufacturer recommendations.

IMPORTANT SAFETY PRECAUTION: All UVGI systems must be inactivated before 

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

might spend time in the men’s sleeping area should be trained in exposure hazards posed by 

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

additional safety training. All initial maintenance and training requirements should be 
Health Hazard Evaluation Report 2012-0265-3183 Page 17

explained by the UVGI system designer/installer. The required maintenance tasks and service 

logs, along with training requirements and logs should be included in the written O&M 

plan recommended above. A subcomponent of this plan should include a UVGI safety plan. 

Complete information on upper-room UVGI system design, 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 staff members find themselves in close contact with guests suspected of being infectious. One example 

would be a van driver transporting clients to/from Community Rehabilitation Center. Ideally, these cases would be identified during the administrative screening process. When these 

circumstances cannot be avoided, it is wise to consider the availability of respiratory protection to protect staff members. 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 Community Rehabilitation Center create a written respiratory protection program 

as outlined in 29 CFR 1910.134, appoint a program administrator, and initiate training and 

initial fit testing for employees. Many online resources exist to assist in the development of a 

respiratory protection program. OSHA has published a Respiratory Protection informational 

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

detailed Small Entity Compliance Guide for the Revised Respiratory Protection Standard 

(http://www.osha.gov/Publications/3384small-entity-for-respiratory-protection-standard-rev.

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

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

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

Labor and Industries has also developed a user-friendly, fillable template that is helpful in developing a respiratory protection program at http://www.lni.wa.gov/Safety/Basics/Programs/

Accident/Samples/RespProtectguide2.doc.

The DCHD, Florida Department of Health, 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. 
Page 18 Health Hazard Evaluation Report 2012-0265-3183

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 

Trinity Rescue Mission needs to take steps to improve staff and volunteer training on symptoms of 

TB disease and prevention of disease transmission. Improved administrative procedures and 

policies need to be established and adopted at the shelter, to help identify guests displaying 

symptoms of TB disease or those listed on the DCHD target screening lists. Improved 

administrative controls would help reduce the potential for future cases of TB disease and 

help bring the ongoing outbreak under control. We also recommend that Trinity work more 

closely with DCHD representatives and use their expertise to help establish a comprehensive, 

written ICP for the shelter. 

From an environmental control perspective, three of the four roof-top AHUs on the men’s 

facility at the shelter were operational and capable of maintaining temperature and air flow, 

although there were issues with improper and inefficient filters. We were unable to verify the 

operability of AHU Men-4 serving the men’s kitchen, since the unit was turned off during our 

visit. It was reported that the AHU is rarely used. All seven of the AHUs in the Women and 

Children’s Center were adequately maintained and fully operational at the time of the NIOSH 

visit, but they also had low efficiency filters installed in each. 

None of the AHUs at Trinity were providing fresh outdoor air to the occupied spaces, as 

required by the 2010 Florida Building Code and ASHRAE guidelines. Given the number of 

guests served by the shelter and the close proximity of guests to one another in most of the 

occupied spaces, it is important that these spaces are receiving adequate amounts of outdoor 

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

serves to dilute infectious aerosols, such as M. tuberculosis droplet nuclei responsible for TB 

transmission. With renovations, the existing AHUs might be made to provide the necessary 

outdoor air, or they could be augmented with the installation of new, dedicated outdoor air 

systems to provide the necessary outdoor air. A knowledgeable HVAC engineer should be 

consulted to discuss options for introducing outdoor air to the shelter. 

The men’s sleeping area houses 104 guests nearly every night. Given the occupant density, 

along with the benefit of the 15-feet ceiling height, a complete upper-room UVGI system 

should 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 

applicable NIOSH guidelines. 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 
Health Hazard Evaluation Report 2012-0265-3183 Page 19

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

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

be covered by an OSHA-mandated respiratory protection program.

Essential improvements to administrative controls need to be made at Trinity to reduce 

the likelihood of future TB transmission at the shelter. Additionally, the environmental 

control systems need some attention to further reduce the risk. While ventilation systems 

and other environmental control systems cannot guarantee prevention of future TB disease 

transmission, improving the environmental controls will reduce the potential for airborne 

disease transmission, along with providing better indoor air quality throughout the shelter. 

The following recommendations are aimed at improving the overall infection control program 

at Trinity, with emphasis on improvements to environmental controls so they meet all 

applicable standards and guidelines.

Recommendations 

Based on our assessment of environmental controls at Trinity Rescue Mission, we have 

developed the following list of recommendations, in order of priority:

1. Improve and enhance the TB administrative controls at the shelter and develop a 

written Infection Control Plan.

● Work more closely with the DCHD to screen shelter staff, volunteers, and 

guests for TB disease.

● With input from DCHD, develop specific procedures for handling a suspected 

or confirmed case of TB disease.

● Educate shelter 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 DCHD and the Florida Department of Health. The plan should include:

○ All aspects of the TB infection control program and associated 

responsibilities, especially those functions requiring coordination with 

other agencies, such as the local and state health departments

○ All new and improved administrative controls put in place at Trinity
Page 20 Health Hazard Evaluation Report 2012-0265-3183

○ Input from ventilation staff and/or guests tasked with servicing 

ventilation systems. Obtaining input from ventilation maintenance 

staff serves to strengthen the environmental control section of the plan 

while giving maintenance staff additional insight into the ventilation 

requirements for reducing or preventing airborne disease transmission.

○ Schedule for updating and revising the ICP

2. Introduce the required amounts of fresh outdoor air to all occupied spaces.

● There are multiple options that can allow adequate outdoor air to be supplied 

to the shelter. 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 Florida 

Building Code, ASHRAE, FGI, and CDC guidelines to select the best option 

for Trinity.

● Improve air flow patterns within all occupied spaces, particularly the men’s 

sleeping area and the women’s overnight room. Air flow patterns should 

provide effective ventilation and temperature control while minimizing the 

number of people that air travels across before returning to the AHU. 

3. 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.

4. Create a respiratory separation area in the men’s sleeping area.

● Choose a reputable ventilation or engineering design contractor that is familiar 

with current Florida Building Code, ASHRAE, FGI, and CDC guidelines and 

recommendations. Ideally a small room should be constructed in a corner of 

the sleeping area specifically for respiratory separation. If construction of a 

separate room is impractical, a less-desirable approach is to install impervious 

retractable partitions that could be used to enclose a corner of the men’s 

sleeping area when respiratory separation is warranted. The partitions should 

touch the floor and extend as close to the ceiling as possible. While there are 

various ways to develop a respiratory separation area, it should include the 

following:

○ Ensure that all supply and return ductwork for the AHU serving the 

newly-constructed room or area enclosed by partitions is intact and 

sealed. Install tight-sealing return dampers on each return from the 

selected transition room to eliminate return air flow when the space 

is used for respiratory separation. Ensure that supply air diffusers 
Health Hazard Evaluation Report 2012-0265-3183 Page 21

provide good air mixing and air flow patterns in a newly-constructed 

room.

○ Design and install an auxiliary exhaust system that enables the 

respiratory separation area to be maintained under negative pressure 

when housing guests for separation purposes. One approach to 

this requirement would be to select and install exhaust fans directly 

through the outside walls of the rooms. The fans can be mounted 

through the walls themselves or mounted on the roof with ductwork 

through the walls to the fans.

○ 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 housing functions to use for 

respiratory separation. The plan should include:

▪ Procedures for moving the guests currently in these areas to 

other locations

▪ Procedures for cleaning and refurnishing the areas for 

separation purposes, and step-by-step procedures for staff to 

follow to start the exhaust fan, close the return air dampers, and 

test for negative pressure

▪ Measures for preparing the areas for back-to-back occupants 

requiring separation

▪ Procedures for cleaning and returning the areas to normal use 

after the need for respiratory separation has passed

○ Operate the new systems 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 room 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.

5. Modify at least one bedroom on the first floor of the women’s shelter into a 

respiratory separation area.

● Choose a reputable ventilation or engineering design contractor that is familiar 

with current Florida Building Code, ASHRAE, FGI, and CDC guidelines 
Page 22 Health Hazard Evaluation Report 2012-0265-3183

and recommendations. 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 

selected room is intact and sealed. Install tight-sealing return dampers 

on each return from the selected room 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 each 

selected 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 walls of the rooms. The fans can be mounted 

through the walls themselves or mounted on the roof with ductwork 

through the walls to the fans. Fan design/placement should ensure 

that the adjacent bathroom stays under negative pressure when the 

bedroom is used for respiratory separation purposes. 

○ 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 each selected room is individually or collectively 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 selected 

room(s) from normal housing functions to use for respiratory 

separation. The plan should include:

▪ Procedures for moving the guests currently in these areas to 

other locations

▪ Procedures for cleaning and refurnishing the areas for 

separation purposes, and step-by-step procedures for staff to 

follow to start the exhaust fan, close the return air dampers, and 

test for negative pressure

▪ Measures for preparing the areas for back-to-back occupants 

requiring separation

▪ Procedures for cleaning and returning the areas to normal use 

after the need for respiratory separation has passed

○ Operate the new systems 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 room is occupied for separation. When 

the room is being used for normal purposes, it should be tested 

monthly to ensure proper operation in the event it would be needed 
Health Hazard Evaluation Report 2012-0265-3183 Page 23

for respiratory separation. The results of all pressure testing should be 

documented.

6. Install an upper-room UVGI system in the men’s sleeping area.

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

with the NIOSH upper-room guidelines, to design, install and test the system. 

The system designer/installer should also provide initial training on exposure 

hazards, safety, and system maintenance.

● The system should be designed to provide UV irradiance levels of at least 

30–50 μW/cm2 in the upper portion of the room while limiting UVC exposure 

to occupants in the area to a level below the NIOSH REL for UVC of 6.0 mJ/

cm2 for an 8-hour exposure time.

● Operate the upper-room UVGI system all day, every day, or at least at all times 

the men’s sleeping area is occupied.

● Establish a UVGI safety, operation, and maintenance program.

● Conduct training and maintenance in accordance with NIOSH guidelines and/

or applicable manufacturer recommendations.

7. Make necessary ventilation changes so clinic examination rooms in the women’s 

shelter are properly maintained under negative pressure in relation to the 

adjacent waiting area. Negative pressure might be established by adjusting existing 

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

supplied to them. If negative pressure cannot be maintained with such adjustments, 

the installation of separate exhaust fans from each space may be required. If new 

exhaust fans are required, they should be operated any time the examination rooms 

are occupied.

8. 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:
Page 24 Health Hazard Evaluation Report 2012-0265-3183

○ Respirator types and proper respirator selection

○ Required medical evaluations for employees prior to respirator use

○ Procedures for initial and annual respirator fit testing

○ Instructions for proper respirator use

○ Information on appropriate respirator maintenance and care

○ Initial and yearly training requirements for respirator users 

○ Procedures for evaluating the effectiveness of the respiratory protection 

program

● Update the respiratory protection program as necessary to reflect changes in 

workplace conditions that affect respirator use.

9. Repair all non-functional bathroom exhaust fans or install new ones. Ensure 

that air is being exhausted from each bathroom and shower facility and that each area 

is under negative pressure, in accordance with the 2010 Florida Building 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.

10. After all of the ventilation systems are updated and functioning properly, 

develop a comprehensive, written HVAC O&M plan. 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

Outline of Future NIOSH Involvement

This report will serve to close out NIOSH Technical Assistance at Trinity. However, we 

understand that the work outlined in the recommendations above will take several months to 
Health Hazard Evaluation Report 2012-0265-3183 Page 25

complete and will represent a significant investment of time and financial resources. As the 

work proceeds, NIOSH could assist by:

● Reviewing any Requests for Proposal developed to initiate the bidding process 

● Reviewing any bids received in response to Requests for Proposals for 

technical content

● Providing technical assistance related to any environmental control strategies, 

including upper-room UVGI systems

It is not necessary for NIOSH to be on-site during any 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

● Final project documents, including as-built drawings, sequences of operations, 

and proper equipment set points

Once the renovations are complete, if additional NIOSH assistance is desired or warranted, 

the request for technical assistance can be reopened.
Page 26 Health Hazard Evaluation Report 2012-0265-3183

References

ACGIH (American Conference of Governmental Industrial Hygienists) [2012]. Threshold 

limit values for chemical substances and physical agents & biological exposure indicies. 

Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ANSI/ASHRAE (American National Standards Institute/American Society of Heating, 

Ventilating and Air-Conditioning Engineers) [2007]. Method of testing general 

ventilation air-cleaning devices for removal efficiency by particle size. Atlanta, GA: 

American Society of Heating, Refrigerating and Air-Conditioning Engineers. Standard 

52.2-2007.

ANSI/ASHRAE [2010a]. Ventilation for acceptable indoor air quality. Atlanta, GA: American 

Society of Heating, Refrigerating and Air-Conditioning Engineers. Standard 62.1-2010. 

ANSI/ASHRAE [2010b]. Thermal environmental conditions for human occupancy. Atlanta, 

GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers. 

Standard 55-2010.

ASHRAE [2011]. Ultraviolet air and surface treatment. In: ASHRAE Handbook – HVAC 

Applications, Chapter 60. Atlanta, GA: American Society of Heating, Refrigerating and 

Air-Conditioning Engineers.

ASHRAE [2012]. Ultraviolet lamp systems. In: ASHRAE Handbook – HVAC Systems and 

Equipment, Chapter 17. Atlanta, GA: American Society of Heating, Refrigerating and 

Air-Conditioning Engineers.

Barry MA, Wall C, Shirley L, Bernardo J, Schwingl P, Brigandi E, Lamb GA [1986]. 

Tuberculosis screening in Boston’s homeless shelters. Public Health Rep 101(5):487-498.

Brickner PW, Vincent RL, First M, Nardell E, Murray M, Kaufman W [2003]. The application 

of ultraviolet germicidal irradiation to control transmission of airborne disease: 

bioterrorism countermeasure. Public Health Rep 118:99-118.

CDC (Centers for Disease Control and Prevention) [1985]. Drug-resistant tuberculosis 

among the homeless—Boston. MMWR 34:429-431.

CDC [1992]. Prevention and control of tuberculosis among homeless persons (ACET). 

MMWR 41(RR-5):001.

CDC [2003a]. Tuberculosis outbreak in a homeless population—Portland, Maine, 2002-2003. 

MMWR 52(48):1184-1185.

CDC [2003b]. TB outbreak among homeless persons—King County, Washington, 2002-2003. 

MMWR 52(49):1209-1210.
Health Hazard Evaluation Report 2012-0265-3183 Page 27

CDC [2005a]. Tuberculosis transmission in a homeless shelter population—New York, 2000-

2003. MMWR 54(06):149-152.

CDC [2005b]. Guidelines for preventing the transmission of Mycobacterium tuberculosis in 

health-care settings, 2005. MMWR 54(RR-17):1-141.

CDC [2006]. Prevention and control of tuberculosis in correctional and detention facilities: 

Recommendations from CDC. MMWR 55(RR-9):1-54.

David HL [1973]. Response of mycobacteria to ultraviolet light radiation. Am Rev Respir Dis 

108:1175-85.

EPA (US Environmental Protection Agency) [2012]. The inside story: A guide to indoor air 

quality http://www.epa.gov/iaq/pubs/insidestory.html. Date accessed: February 22, 2013.

FGI (Facility Guidelines Institute) [2010]. Guidelines for design and construction of health 

care facilities. Chicago, IL: American Society for Healthcare Engineering of the American 

Hospital Association.

First MW, Nardell EA, Chaisson W, Riley R [1999a]. Guidelines for the application of 

upper-room ultraviolet germicidal irradiation for preventing transmission of airborne 

contagion - part I: basic principles. ASHRAE Trans 105(1):CH-99-12-91.

First MW, Nardell EA, Chaisson W, Riley R [1999b]. Guidelines for the application of 

upper-room ultraviolet germicidal irradiation for preventing transmission of airborne 

contagion - Part II: design and operation guidance. ASHRAE Trans 105(1):CH-99-12-92.

ICC (International Code Council, Inc.) [2011]. Florida building code 2010: Mechanical 

(chapter 4, ventilation). Country Club Hills, IL: International Code Council, Inc.

Knopf SA [1914]. Tuberculosis as a cause and result of poverty. J Am Med Assoc 63(20):1720-

1725.

McAdam JM, Brickner PW, Scharer LL, Crocco JA, Duff AE [1990]. The spectrum of 

tuberculosis in a New York City men’s shelter clinic (1982-1988). Chest 97:798-805.

McLean RL [1961]. General discussion: the mechanism of spread of Asian influenza. Am Rev 

Respir Dis 83:29-40.

NIOSH [1972]. Criteria for a recommended standard: occupational exposures to ultraviolet 

radiation. By Seiter RE. Cincinnati, OH: U.S. Department of Health, Education, and 

Welfare, Health Services and Mental Health Administration, National Institute for 

Occupational Safety and Health, DHEW (NIOSH) Publication No. HSM-73-11009.

NIOSH [2009]. Environmental control for tuberculosis: basic upper-room ultraviolet 

germicidal irradiation guidelines for healthcare settings. By Whalen J. Cincinnati, OH: 

U.S. Department of Health and Human Services, Centers for Disease Control and 

Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) 
Page 28 Health Hazard Evaluation Report 2012-0265-3183

Publication No. 2009-105. http://www.cdc.gov/niosh/docs/2009-105/pdfs/2009-105.pdf. 

Date accessed: March 22, 2013.

Nolan CM, Elarth AM, Barr H, Saeed AM, Risser DR [1991]. An outbreak of tuberculosis in 

a shelter for homeless men: A description of its evolution and control. Am Rev Respir Dis 

143:257-261.

Riley RL, Wells WF, Mills CC, Nyka W, McLean RL [1957]. Air hygiene in tuberculosis: 

quantitative studies of infectivity and control in a pilot ward. Am Rev Tubercul 75:420-

31.

Riley RL, Mills CC, O’Grady F, Sultan LU, Wittstadt F, Shivpuri DN [1962]. Infectiousness of 

air from a tuberculosis ward. Am Rev Respir Dis 85:511-25.

Riley RL, Knight M, Middlebrook G [1976]. Ultraviolet susceptibility of BCG and virulent 

tubercle bacilli. Am Rev Respir Dis 113:413-18.

Riley RL, Nardell EA [1989]. Clearing the air: the theory and application of ultraviolet air 

disinfection. Am Rev Respir Dis 139(5):1286-94.

Slutkin G [1986]. Management of tuberculosis in urban homeless indigents. Public Health 

Rep 101(5):481-485.

Wells WF, Holla, WA [1950]. Ventilation in the flow of measles and chickenpox through a 

community: progress report, January 1, 1946 to June 15, 1949—airborne infection study, 

Westchester County department of health. J Am Med Assoc 142:1337-44.

Willmon TL, Hollaender A, Langmuir AD [1948]. Studies of the control of acute respiratory 

diseases among naval recruits. I. a review of a four-year experience with ultraviolet 

irradiation and dust suppressive measures, 1943 to 1947. Am J Hyg 48:227-32.

Xu P, Peccia J, Fabian P, Martyny JW, Fennelly KP, Hernandez M, Miller SL [2003]. Efficacy 

of ultraviolet germicidal irradiation of upper-room air in inactivating airborne bacterial 

spores and mycobacteria in full-scale studies. Atmos Environ 37:405-19.
Health Hazard Evaluation Report 2012-0265-3183 Page 29

Table 1. General air-handling unit (AHU) information

NIOSH 

AHU 

Identifier

Physical Location 

of AHU

Location Served

 by AHU (floor/building)A

AHU 

ManufacturerB AHU Model NumberB

Proper Filter 

Configuration in 

AHUC,D

Actual Filter 

Configuration in 

AHUB,D,E

Men-1 Rooftop of Men’s Facility Men’s Sleeping Area Carrier 50HJQ012 (4) 20 × 20 × 2 *(4) 18 × 14 × 2FMen-2 Rooftop of Men’s Facility Men’s Facility Chapel Area Carrier 50TJQ008 (4) 16 × 20 × 2 *(4) 18 × 14 × 2FMen-3 Rooftop of Men’s Facility Men’s Facility Dining Area Goodman CPH090XXX3BXXXAA (4) 16 × 24 × 2 (4) 16 × 24 × 2Men-4 Rooftop of Men’s Facility Men’s Facility Kitchen Carrier 50TJQ012 (4) 20 × 20 × 2 *(4) 18 × 14 × 2F

Women-1G Women’s Facility (1st Floor Mechanical Room) Women’s Facility (1st Floor/ Undetermined)H Carrier 40RMQ016 (4) 16 × 24 × 2 and (4) 16 × 20 × 2 (4) 16 × 24 × 2 and (4) 16 × 20 × 2Women-2G Women’s Facility (1st Floor Mechanical Room) Women’s Facility (1st Floor/ Undetermined)H Carrier FK4DNF003 (1) 21 × 20 × 1 (1) 21 × 20 × 1Women-3G Women’s Facility (1st Floor Mechanical Room) Women’s Facility (1st Floor/ Undetermined)H Carrier FK4DNF005 (1) 21 × 20 × 1 (1) 21 × 20 × 1Women-4G Women’s Facility (Attic)

Women’s Facility (2ndFloor/ Rooms 18-19, D2, and laundry room)I

Carrier FK4DNB006 (1) 21 × 24 × 1 (1) 21 × 24 × 1

Women-5G Women’s Facility (Attic)

Women’s Facility (2ndFloor/ Rooms 14-17 and partially showers/restroom)I

Carrier FK4DNF003 (1) 21 × 20 × 1 (1) 21 × 20 × 1

Women-6G Women’s Facility (Attic)

Women’s Facility (2ndFloor/ Rooms 10-13 and partially showers/restroom)I

Carrier FK4DNF005 (1) 21 × 20 × 1 (1) 21 × 20 × 1

Women-7G Women’s Facility (Attic) Women’s Facility (2nd Floor/ Rooms 7-9 and D1)I Carrier FK4DNB006 (1) 21 × 24 × 1 (1) 21 × 24 × 1

A May not represent all locations served by the AHUB Information taken during visual inspection of AHUC Information gathered from product data specific to each AHU model published by respective AHU manufacturer.D Value in parenthesis represents the number of filters; dimensions are width × height × depth in units of inchesE Entries preceded by an asterisk (*) represent actual filter configurations that differ from published proper filter configurations. Differences could be due to incorrect filter  size(s) being installed or because the AHU manufacturer modified the AHU model size/filter recommendation as the product was updated.F Filters in this AHU appeared to be homemade and not commercially available. Therefore, no information on filter performance was available.G All supply ductwork from the AHU was wrapped in fiberglass.H It was not determined which AHU(s) supplied air to individual spaces on the first floor of the Women’s Facility. Doing so would have required unfettered access to thermo stats and/or removing multiple ceiling tiles. This would have caused a significant disruption to staff and guests on the first floor at the time.I The locations served by the 2nd floor AHUs in the Women’s Facility was determined by turning various thermostats on and off. Information may not be entirely correct.

Tables
Page 30 Health Hazard Evaluation Report 2012-0265-3183 Table 2. Applicable outdoor air supply flow rates, minimum exhaust air flow rates, and default occupancy densities from the 2010 Florida Building Code and ASHRAE Standard 62.1-2010A 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 — 20 Bedrooms/Living Rooms 5 0.06 — 10 Office Spaces 5 0.06 — 5 Conference Rooms 5 0.06 — 50 Multipurpose Assembly Spaces 5 0.06 — 120 Reception Areas 5 0.06 — 30 Break RoomsF 5F 0.12F — 50F Central Laundry RoomsF 5F 0.12F — 10F Occupiable Dry Storage RoomsF 5F 0.06F — 2F Occupiable Liquid/Gel Storage RoomsF 5F 0.12F — 2F Unoccupiable Storage RoomsG — 0.12G — — Lobbies/Prefunction Spaces 7.5 0.06 — 30 Lecture Classrooms 7.5 0.06 — 65 Computer Labs 10 0.12 — 25 Dining Rooms 7.5 0.18 — 70 Central Kitchens 7.5F 0.12F 0.7 cfm/ft2 C 70 Public Bathrooms — — 50 or 70 cfm/toilet and/or urinalH — Private Bathrooms — — 25 or 50 cfmI — Shower RoomsG — — 20 or 50 cfm/shower headG,J — A Requirements published in: 2010 Florida Building Code: Mechanical (Chapter 4, Ventilation). International Code Council, Inc., Country Club Hills, IL (2011) and American National Standards Institute (ANSI)/American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Ventilation for Acceptable Indoor Air Quality, Standard 62.1- 2010. ASHRAE, Atlanta, GA (2010). In nearly all cases, the 2010 Florida Building Code has adopted ventilation recommendations directly from ASHRAE Standard 62.1-2010. B cfm/person = cubic feet per minute (also commonly shown as ft3/min) per person typically in the occupied space C cfm/ft2 = cubic feet per minute (also commonly shown as ft3/min) per square feet of occupied space D Mechanical exhaust should be released directly outdoors at least 25 feet away from air intakes. Recirculation of exhaust air back into the building should be avoided. E #/1000ft2 = number of people per 1000 square feet of occupied space. These values are typical 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 62.1-2010. No directly corresponding values appear in the 2010 Florida Building Code. G Requirements are only published in the 2010 Florida Building Code. No directly corresponding values appear in ASHRAE Standard 62.1-2010. H 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 antici pated, the lower rate may be used. I These rates are for bathrooms intended for use by one person at a time. 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. J 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 2012-0265-3183 Page 31 Table 3. Total air delivered by ventilation systems, occupant densities, and recommended outdoor air flow SpaceA AHU Serving Space Return Flow from Space (cfm)B Supply Flow into Space (cfm)B Approximate Area of Space (ft2)C Typical Occupants in SpaceD Occupant Density (#/1000 ft2)D,E,F Recommended Outdoor Air Flow (cfm)B,G Men’s Facility Reception/Lobby Area UndeterminedH <30I 130 390 3 8 38.4 Sleeping Area Men-1 2435 3110 2530 104 *41 671.8 Bathroom/Showers off Sleeping Area Men-1 520 0I 440 N/AJ N/AJ N/AJ Chapel/Dining Area Men-2 (chapel) and Men-3 (dining) 3680 4410 3105 140 45 886.3/1608.9K 1st Floor – Women’s Facility Reception/Lobby Area and Hallway UndeterminedH 285 890 1220 2 2 83.2 Dining Area/Classroom UndeterminedH 300 1245 940 30 32 206.4/394.2K Play Room UndeterminedH 130 150 425 4 9 45.5 Restroom in Play Room UndeterminedH 0I 40 65 N/AJ N/AJ N/AJ Clinic Waiting Area UndeterminedH 260 40 95 2 21 15.7 Clinic Office UndeterminedH 115 80 45 1 22 7.7 Clinic Exam Room #1L UndeterminedH 0I 70 80 2 25 14.8 Clinic Exam Room #2L UndeterminedH ObsM 50 70 2 29 14.2 Clinic Back Room/Storage UndeterminedH 160 70 35 0 0 4.2 Clinic Restroom UndeterminedH 0I 70 40 N/AJ N/AJ N/AJ Women’s Overnight Sleeping Room UndeterminedH 470 570 505 18 *36 120.3 Women’s Overnight Restroom UndeterminedH 0I 0I 75 N/AJ N/AJ N/AJ Room #1 UndeterminedH 50 105 195 1 5 16.7 Room #1 Bathroom UndeterminedH 0I 0I 30 N/AN N/AN N/AN Room #2 UndeterminedH 95 140 195 5 *26 36.7 Room #2 Bathroom UndeterminedH 0I 0I 30 N/AN N/AN N/AN Room #3 UndeterminedH 40 130 195 1 5 16.7 Room #3 Bathroom UndeterminedH 0I 0I 30 N/AN N/AN N/AN Room #4 UndeterminedH 110 180 195 4 *21 31.7 Room #4 Bathroom UndeterminedH 0I 0I 30 N/AN N/AN N/AN Room #5 UndeterminedH 100 140 230 3 13 28.8
Page 32 Health Hazard Evaluation Report 2012-0265-3183 Table 3 (continued). Total air delivered by ventilation systems, occupant densities, and recommended outdoor air flow SpaceA AHU Serving Space Return Flow from Space (cfm)B Supply Flow into Space (cfm)B Approximate Area of Space (ft2)C Typical Occupants in SpaceD Occupant Density (#/1000 ft2)D,E,F Recommended Outdoor Air Flow (cfm)B,G 1st Floor – Women’s Facility Room #5 Bathroom UndeterminedH 0I 0I 35 N/AN N/AN N/AN Room #6 UndeterminedH 110 170 195 2 10 21.7 Room #6 Bathroom UndeterminedH 0I 0I 65 N/AN N/AN N/AN 2nd Floor – Women’s Facility Room D1 Women-7O 440 540 805 12 15 108.3 Room #7 Women-7O 155 160 240 4 17 34.4 Room #8 Women-7O 155 175 240 4 17 34.4 Room #9 Women-7O 140 225 240 4 17 34.4 Room #10 Women-6O 130 130 240 4 17 34.4 Room #11 Women-6O 130 190 240 4 17 34.4 Room #12 Women-6O 160 195 240 4 17 34.4 Room #13 Women-6O 135 180 240 4 17 34.4 Room #14 Women-5O 135 210 240 4 17 34.4 Room #15 Women-5O 140 215 240 4 17 34.4 Room #16 Women-5O 125 170 240 4 17 34.4 Room #17 Women-5O 140 230 240 4 17 34.4 Room #18 Women-4O 120 200 240 4 17 34.4 Room #19 Women-4O 240 200 240 4 17 34.4 Room D2 Women-4O 580 260 370 6 16 52.2 Showers and Restroom Women-5 & Women-6O 720 575 945 N/AJ N/AJ N/AJ Laundry Room Women-4O 795 335 240 1 4 33.8 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
Health Hazard Evaluation Report 2012-0265-3183 Page 33 F Entries preceded by an asterisk (*) represent spaces where the actual occupant density likely exceeds the default occupant density presented in Table 2. G Calculated based on recommendations published in: American National Standards Institute (ANSI)/American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Ventilation for Acceptable Indoor Air Quality, Standard 62.1-2010. ASHRAE, Atlanta, GA (2010) and the 2010 Florida Building Code: Mechanical (Chapter 4, Ventilation). International Code Council, Inc., Country Club Hills, IL (2011). In nearly all cases, the 2010 Florida Building Code has adopted ventilation recommendations directly from ASHRAE Standard 62.1-2010. H It was not determined which AHU(s) supplied air to this space. Doing so would have required unfettered access to thermostats and/or removing multiple ceiling tiles. This would have caused a significant disruption to staff and guests on the first floor at the time. I A TSI Accubalance Plus, Model 8373, was used to determine air flow measurements. The instrument is unable to accurately read volumetric air flow rates less than 30 cfm. Reading could be anywhere between 0 and 30 cfm. In these cases, ventilation fog was used to visually determine if any air was flowing through the vent/grille. When there was visual confirmation of air flow, the result was reported as < 30 cfm. When air flow could not be verified visually, the result was reported as 0 cfm. J N/A = not applicable. Neither ASHRAE Standard 62.1-2010 nor the 2010 Florida Building Code include outdoor air recommendations for restrooms, bathrooms, and shower facili ties. Instead, for public bathrooms, the recommendation is 50 cfm of exhaust from the space per toilet or urinal when periods of heavy use are not expected. ASHRAE 62.1-2010 does not specifically address ventilation for showers. However, the 2010 Florida Building Code: Mechanical (Chapter 4, Ventilation) specifies 50 cfm of exhaust air from the space per shower head when the exhaust system is designed to operate intermittently (e.g., exhaust fan connected to light switch) or 20 cfm per shower head for exhaust systems designed to operate continuously. Water closet and shower exhaust may be made up entirely of transfer air from adjacent spaces (i.e., no direct supply air to the space is required) and only a maximum of 10% of the exhaust air is permitted to be recycled. K ASHRAE Standard 62.1-2010 and the 2010 Florida Building Code: Mechanical (Chapter 4, Ventilation) provide separate outdoor air recommendations for assembly spaces and dining rooms. Both numbers are reported here (assembly space/dining area). L Areas where medical examinations and/or procedures are performed should be maintained under negative pressure compared to adjacent areas (i.e., more air should be exhausted from the space than is supplied to the space). Exam Room #1 was under positive pressure during the NIOSH visit. The pressure relationship between inside and outside of Exam Room #2 was not determined. M Obs = obstructed. Air flow measurements could not be taken because the exhaust grille was obstructed. Exhaust was determined to be working via ventilation fog testing. N N/A = not applicable. Living areas on the first floor of the Women’s Facility are equipped with private bathrooms. ASHRAE Standard 62.1-2010 and the 2010 Florida Building Code: Mechanical (Chapter 4, Ventilation) specifies 25 cfm of exhaust air per toilet. This exhaust air may be made up entirely of transfer air from adjacent spaces (i.e., no direct supply air to the space is required) and only a maximum of 10% of the exhaust air is permitted to be recycled. O The locations served by the 2nd floor AHUs in the Women’s Facility were determined by turning various thermostats on and off. Information may not be entirely correct.
Page 34 Health Hazard Evaluation Report 2012-0265-3183

Table 4. ASHRAE indoor relative humidity and temperature recommendationsA

Relative Humidity Winter TemperaturesB Summer TemperaturesB

30%C 69.5°F to 77.0°F 75.5°F to 81.5°F

40% 69.0°F to 76.5°F 75.5°F to 81.0°F

50%D 68.5°F to 76.0°F 75.0°F to 80.5°F

A Adapted from: American National Standards Institute (ANSI)/American Society of Heating, Refrigerating and Air- 

 Conditioning Engineers (ASHRAE). Thermal Environmental Conditions for Human Occupancy, Standard 55-2010. 

 ASHRAE, Atlanta, GA. (2010).

B Applies to occupants wearing typical summer and winter clothing, with a sedentary to light activity level

C Humidity levels below 30% may cause irritated mucus membranes, dry eyes, and sinus discomfort.

D The U.S. Environmental Protection Agency recommends maintaining indoor relative humidity below 60% and ideally in 

 a range from 30% to 50% to prevent mold growth.
Health Hazard Evaluation Report 2012-0265-3183 Page 35

Figure 1. A reprensentative ventilation filter from inside AHU Men-1, AHU Men -2, and 

AHU Men-4.

Figures
Page 36 Health Hazard Evaluation Report 2012-0265-3183

Figure 2. Typical upper-air UVGI installations: Left–Wall-mounted fixture with louvers 

installed in a health clinic; Right–Ceiling-mounted fixture with a fan installed in a homeless 

shelter.
Health Hazard Evaluation Report 2012-0265-3183 Page 37

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Page 38 Health Hazard Evaluation Report 2012-0265-3183

The Health Hazard Evaluation Program investigates possible health hazards in the 

workplace under the authority of Section 20(a)(6) 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 control 

occupational health hazards and to prevent occupational illness and disease. Regulations 

guiding the Program can be found in Title 42, Code of Federal Regulations, Part 85; 

Requests for Health Hazard Evaluations (42 CFR 85).

Acknowledgments

This report was prepared by Stephen B. Martin, Jr., R. Brent Lawrence, and Michael C. 

Beaty of the Field Studies Branch (FSB), Division of Respiratory Disease Studies (DRDS) 

and Kenneth R. Mead of the Engineering and Physical Hazards Branch, Division of Applied 

Research and Technology. Desktop publishing was performed by Tia McClelland (FSB/

DRDS).

Availability of Report

Copies of this report have been sent to representatives from Trinity Rescue Mission, DCHD, 

the Florida Department of Health, CDC/NCHHSTP/DTBE, and the OSHA Regional Office. 

This report is not copyrighted and may be freely reproduced. 

This report is available at http://www.cdc.gov/niosh/hhe/reports/pdfs/2012-0265-3183.pdf.

Recommended citation for this report:

NIOSH [2013]. Health hazard evaluation report: Evaluation of 

Environmental Controls at a Homeless Shelter (Trinity Rescue Mission) 

Associated with a Tuberculosis Outbreak – Florida. By Martin, Jr. SB, 

Mead KR, Lawrence RB, Beaty MC. Morgantown, WV: U.S. Department of 

Health and Human Services, Centers for Disease Control and Prevention, 

National Institute for Occupational Safety and Health, NIOSH Report No. 

2012-0265-3183.
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

Delivering on the Nation’s promise:

Safety and health at work for all people through research and prevention