Health Hazard Evaluation Report 2012-0263-3181 Page 1

Evaluation of Environmental Controls at a Social 

Assistance Facility (Community Rehabilitation Center) 

Associated with a Tuberculosis Outbreak – Florida

Report No. 2012-0263-3181

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 2012-0263-3181

Contents

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

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

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

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

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

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

Results & Discussion ...................................... 4

Conclusions ................................................... 13

Recommendations ...................................... 14

Outline of Future NIOSH Involvement .... 17

References ..................................................... 18

Tables ............................................................. 20

Acknowledgements .................................... 28

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 2012-0263-3181 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 Community Rehabilitation Center, a local social 

assistance facility with epidemiological links to an ongoing tuberculosis outbreak.

What NIOSH Did

● We visited Community Rehabilitation Center on August 21, 2012.

● We met with representatives from the Duval County Health Department and 

Community Rehabilitation Center to discuss the ongoing tuberculosis outbreak.

● We recorded the physical sizes of occupied spaces.

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

● We collected information on facility air-handling units.

What NIOSH Found

● Community Rehabilitation Center was working in conjunction with the Duval County 

Health Department to improve administrative controls to identify guests on priority 

screening lists or those with symptoms of tuberculosis.

● Central air-handling units in the main building were in good working order and had 

proper filter configurations installed.

● Some window ventilation units in the old portion of the main building were not 

operational.

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

systems.

● A written respiratory protection plan did not exist.

● Most bathroom exhaust fans were not properly maintaining the spaces under negative 

pressure.

What Community Rehabilitation Center Should Do

● Continue to work with the Duval County Health Department to improve overall 

administrative controls and help ensure rapid identification of guests suspected to have 

tuberculosis.

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

Health Department and Florida Department of Health.

● Modify facility ventilation systems to provide adequate fresh outdoor air to all 

occupied spaces using a strategy compatible with existing system capacities.

● Replace all existing packaged terminal air conditioner units in the old portion of the 
Page ii Health Hazard Evaluation Report 2012-0263-3181

main building with a new, efficient central air-handling unit.

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

operation of each air-handling unit.

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

requirements of the Occupational Safety and Health Administration’s respiratory 

protection respiratory protection standard 29 Code of Federal Regulations 1910.134.

● Adjust supply air flow into bathrooms so spaces are maintained under negative 

pressure during occupancy and repair or replace bathroom exhaust fans not meeting 

performance specifications.

● Develop and implement a written operation and maintenance plan for all facility 

heating, ventilation, and air-conditioning systems, to include a filter replacement 

schedule.
Health Hazard Evaluation Report 2012-0263-3181 Page iii

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Page iv Health Hazard Evaluation Report 2012-0263-3181

Abbreviations

μm Micrometer

AHU(s) Air-handling unit(s)

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

ft2 Square feet

HVAC Heating, ventilation, and air-conditioning

ICP Infection control plan

MERV Minimum efficiency reporting value

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

PTAC Packaged terminal air conditioner

RH Relative humidity

TB Tuberculosis
Health Hazard Evaluation Report 2012-0263-3181 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 

were accessible as of the publication date of this report.
Health Hazard Evaluation Report 2012-0263-3181 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 Community Rehabilitation Center social assistance facility in August 2012, we collected physical and ventilation measurements in all key areas of the 

facility. We focused on areas where guests 

typically congregate or spend significant 

amounts of time. We recorded the make 

and model number of 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 facility guests. With the exception 

of some window units in the older portion 

of the main building, the AHUs 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 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, Community Rehabilitation Center has taken numerous steps 

to improve administrative controls, particularly when it comes to identifying guests showing 

signs and symptoms of TB. We recommend additional improvements to the administrative 

and environmental controls at the center. From a ventilation standpoint, we suggest that all 

occupied spaces in the facility are supplied adequate amounts of outdoor air. We also recommend developing a written infection control plan, HVAC operation and maintenance plan, 

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

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

respiratory disease.

NIOSH investigators conducted an assessment of environmental controls in Community Rehabilitation Center, a 

social assistance facility 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 2012-0263-3181

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 Community Rehabilitation Center. It details and prioritizes our recommendations for improving 

environmental controls at the facility, and outlines the current plan for future NIOSH involvement. 

Background

Tuberculosis and Homeless Populations

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

Keywords: NAICS 624310 (Vocational Rehabilitation Services), tuberculosis, environmental controls, ventilation, adult education facility, airborne infection, airborne 

transmission, respiratory
Health Hazard Evaluation Report 2012-0263-3181 Page 3

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]. 

Community Rehabilitation Center 

The Community Rehabilitation Center social assistance facility was established in 1993 and 

is primarily an outpatient mental health facility serving people in Duval and surrounding 

counties. The facility offers behavioral care, primary care, and community economic development services for individuals at the poverty level with mental illness, substance abuse or 

HIV/AIDS. It employs more than 60 professionals that work in all service areas provided by 

the center. Approximately 160 clients come to the facility each day to participate in educational and vocational day programs between 9:00 AM–12:00 PM and/or 2:00 PM–6:00 PM. 

Transportation to/from the facility is provided for clients that need it. This facility differed 

from the other three we visited in that it was the only facility that did not house overnight 

clients.

The main structure is a 16,000 square feet (ft2), one-story masonry building. The building is 

divided nearly in half between newer and older portions. The newer portion houses the main 

entrance and reception areas, two large dining/activity areas that can be opened up to one 

large space, a kitchen, conference room, and many staff offices. The new portion is equipped 

with two central heating and air conditioning systems that provide ventilation to all spaces 

in that section of the facility. The older portion of the structure houses several staff offices, a 

break room, and seven team rooms. Four team rooms are on one side of a hallway, and three 

are on the other. Dividers between the team rooms can be opened and closed to combine/

separate spaces to house classes of various sizes. Most of the staff offices in the old building 

are ventilated by one rooftop air-handling unit. However, the team rooms and offices down 

the longest hallway are ventilated with under-window packaged terminal air conditioner 

(PTAC) units.

Adjacent to the main building are two trailers used as counseling areas for clients and a small 

two-story masonry drop-off building. The smaller of the two trailers has an office and adult 

education area. It is ventilated by a central HVAC unit installed on one end. The larger 

trailer has two central HVAC units providing ventilation to six offices, a waiting area, and 

reception space. The drop-off building has a central AHU in the attic that provides ventilation to a large client gathering area on the first floor. Clients use this space before and after 

scheduled programs and during periods of bad weather. 

In 2006, Community Rehabilitation Center expanded their services to include a thrift shop 

and a screen print shop located near the main building. However, these facilities were not 

visited as part of our technical assistance response.
Page 4 Health Hazard Evaluation Report 2012-0263-3181

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 Community Rehabilitation Center 

and two of the three other homeless facilities to be visited were in attendance. 

We arrived at Community Rehabilitation Center on Tuesday, August 21, 2012 and signed into 

the building. After we unloaded our equipment, the facilities manager provided us with floor 

plans of the main building and led a tour of the entire facility. After the tour, we began taking 

physical and ventilation measurements in all key areas. We focused on areas where clients 

typically congregate or spend significant amounts of time, but measurements were taken 

throughout the entire facility.

We recorded the make and model number of all central AHUs providing supply air to the 

facility, and we visually inspected 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 an appropriate air capture hood. 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 met briefly with the Community Rehabilitation Center 

facilities manager on the afternoon of August 22, 2013 to discuss our general findings from 

our previous day’s assessment. A formal closing meeting for our on-site response to the 

technical assistance request for all four of the 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. 

 

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 
Health Hazard Evaluation Report 2012-0263-3181 Page 5

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 this social assistance facility, or in areas where administrative controls alone are inadequate, environmental controls and respiratory protection should 

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

Administrative Controls

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

Department of Health, DCHD, and Community Rehabilitation Center, it was apparent that 

limited TB administrative controls were in place at the facility prior to the current disease 

outbreak. However, efforts were taken to improve the overall administrative controls in place 

at the time of the site visit. Employees were trained on symptoms of TB disease and prevention of TB transmission. Additionally, intake screening procedures are now in place to help 

identify clients on target screening lists, or others suspected of having TB, and refer them to 

DCHD for critical medical screening. These procedures will help identify infected individuals more rapidly in the future and serve to help keep infected clients away from those that are 

healthy. 

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

overall mission of the facility typically results in services being provided to large numbers 

of clients, often in close proximity to one another. This is particularly the case in the dining/assembly areas and the team rooms. Even the best ventilation systems are incapable of 

preventing the spread of disease between two clients close to one another. Thus, identifying 

people with suspected disease, keeping them separated from the general client population, 

and following up with appropriate medical evaluations and treatment (if necessary) are the 

most important elements of reducing or eliminating the spread of disease. 

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

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

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

ICPs and TB ICP templates 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 further strengthen the written plan. These ICPs are particularly useful when overall TB infection control requires the coordination and subsequent 

follow-up of different agencies. In response to this current TB outbreak, there was good 

communication and coordination between Community Rehabilitation Center and DCHD. 

However, 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 
Page 6 Health Hazard Evaluation Report 2012-0263-3181

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

Environmental Controls

General Ventilation System Information

General information on the central AHUs at Community Rehabilitation Center, including the 

areas served by each unit, is provided in Table 1. All three of the central AHUs supplying 

air to the main building were fairly new, and on the day of our visit, were fully maintaining 

temperature set points and air flow. AHU-1 and AHU-2, servicing the newer portion of the 

building, were installed in a mechanical room adjacent to the Executive Director’s office. In 

addition to housing the two AHUs, the mechanical space was also used for storage. Gaining 

access to the AHUs was difficult because of the additional clutter in the space, but it was determined that the two AHUs were manufactured in late 2000 or early 2001. AHU-3, a rooftop unit that services part of the older section of the building, was manufactured in June 2012 

and installed just prior to our visit. Each of the main building AHUs supply air to occupied 

spaces through galvanized steel supply ducts. Return air flows back to the units in the new 

portion of the building through ducted returns. Return air back to AHU-3 is mainly via a ceiling plenum, with air from the occupied spaces traveling to the plenum around light fixtures 

and through holes in the drop ceiling. All three of these central AHUs had properly-sized 

filter configurations during our visit. However, none of the units delivered fresh, outdoor air 

to the occupied spaces. The configuration for AHU-3 had dedicated capacity for introducing 

outdoor air, but the outdoor air dampers were sealed shut and not operable. 

The window PTAC units installed along the longest hallway of the older portion of the main 

building were from various manufacturers. While most appeared to be functional, some 

were not in use during our visit. Information on the make/model of each PTAC unit was not 

recorded since the units were not intended to bring in any fresh, outdoor air and only served 

to condition and recirculate air within the same space(s) they served.

The AHUs in the two trailers appeared to be installed during the production of the trailers themselves. While the two units servicing the large trailer were produced by Eubank 

Manufacturing Enterprises (Longview, Texas), an exact date of manufacturing could not be 

determined. All of the labels and stickers on the single AHU servicing the small trailer were 

missing or faded to the point they could not be read (see Table 1). These units provided supply air through ductwork installed in the ceiling of each trailer. Return air to the trailer AHUs 

traveled through grilles in the walls of the individual spaces, into the main hallway of each 

trailer, and directly back to the AHUs themselves. These AHUs were all equipped with air 

filters.

We were unable to gain access to the AHU servicing the assembly area/game room in the 

drop off building. Thus, the make/model, supply and return schemes, and filter configuration could not be determined. This space was completely unoccupied during the NIOSH visit 

and was only reported to be used for short periods of time before and after classes or during 

periods of bad weather. 

 
Health Hazard Evaluation Report 2012-0263-3181 Page 7

Filtration

All of the ventilation filters used in the main building central AHUs had an American Society 

of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Minimum Efficiency 

Reporting Value (MERV) of 8, which corresponds to a removal efficiency of greater than 

70% for 3.0 to 10 micrometer (μm) particles [ANSI/ASHRAE 2007]. However, MERV 8 

filters are only around 25% 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]. 

The three counseling trailer AHUs appeared to have filters that were hand-cut from a larger 

piece of filter material. These filters were installed immediately behind the return air grilles 

into the AHUs themselves. The filter material installed in these units was not supported by 

any framing, but the material did seem to cover the entire return air opening to each of the 

AHUs. The material used was clearly made of synthetic polymers, but since the filters had 

no markings and appeared to be homemade, there was no way to determine the filtration efficiency of the trailer AHU filters. As mentioned previously, we could not determine which 

filter(s) was/were installed in the Drop Off AHU.

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 all of the facility AHUs 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

With the exception of some of the window PTAC units, all of the AHUs at Community Rehabilitation Center were operational, fairly clean, and appeared to be adequately maintained. 

The facilities manager informed us that the ventilation filters are changed every 4–6 weeks. 

Unfortunately, there was no written plan outlining the preventive maintenance schedules 

and procedures for HVAC systems. A written HVAC operation and maintenance (O&M) 

plan should be developed. Currently, all preventive and emergency maintenance is managed, scheduled, and coordinated by the facilities manager, with assistance from maintenance 

staff. While this seems to be effective at the present time, there could be a void if the facilities manager leaves his current position or is unavailable for any significant period of time. 

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. 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.
Page 8 Health Hazard Evaluation Report 2012-0263-3181

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 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 social assistance facilities, there are 

published guidelines applicable to Community Rehabilitation Center. 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 facility 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. Nearly all of the offices throughout the facility 

show high occupant densities. Yet, most of these offices are only occupied by one person. 

In these cases, the occupant densities are high simply because the offices are smaller than 

typical office spaces. While Table 3 shows numerous office spaces with high occupant densities, none of these areas are particularly of concern, unless these same offices will be used 

for meeting with potentially-infectious clients. However, of particular importance are the 

team rooms located along the long hallway of the old portion of the main building. As shown 

in Table 3, these rooms were ventilated by PTAC units which do not mechanically provide 
Health Hazard Evaluation Report 2012-0263-3181 Page 9

outdoor air to these spaces and are not part of the centralized AHU scheme. Each of the team 

rooms were roughly 12 feet wide by 16 feet deep, which gives an occupiable space of approximately 190 ft2

. If these rooms are considered lecture classrooms (see Table 2), this floor 

space would allow a typical occupant density of only 12 people. Exceeding 12 people in a 

team room could result in an increased risk of airborne disease transmission because of the 

close proximity of one person to another. During our visit, team rooms 18, 19, and 20 had 

their dividers opened to create one large classroom. Counting the instructor, there were 41 

people inside the space of 576 ft2. This corresponds to an occupant density of 71 occupants 

per 1000 ft2, compared to a typical density of only 65 occupants per 1000 ft2. We were told 

that classes this size, and potentially larger, were fairly common in the team rooms. While 

the preferred approach would be to install a centralized AHU to provide sufficient outdoor air 

to meet actual occupancy levels in these rooms, as an interim measure, it would be prudent to 

limit the size of the classes to 12 people or less per team room, whenever possible. If larger 

classes are planned, consider using the larger dining/assembly areas because of the additional 

space available for clients to spread out and the increased filtration and dilution of potential 

infectious aerosols. 

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 Community Rehabilitation Center delivered any fresh outdoor air into the building. 

While AHU-3 and the AHUs in the trailers could easily be modified to bring in outdoor air, 

AHU-1 and AHU-2 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 

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

AHU would require some modifications and result in increased annual energy costs. However, it is important to ensure that all occupied spaces in Community Rehabilitation Center 

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 Community Rehabilitation Center 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 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 trailer AHUs and AHU-3 on the roof of the main building should be made easier by the 

fact that these units are already located outdoors. The system modifications for AHU-1 and 

AHU-2, servicing the newer portion of the main building, and the Drop Off AHU would require more extensive modifications since the outdoor air intakes and dampers would need to 

be installed into the mechanical spaces housing these AHUs. Although incorporating outdoor 
Page 10 Health Hazard Evaluation Report 2012-0263-3181

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 occupied spaces would be to 

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

with ductwork extending to all occupied spaces of the main building. This strategy could 

also be applied separately to the trailers and drop off building. This new AHU would be 

sized to provide adequate outdoor air flow for the entire main building (approximately 2000 

cfm) while also providing the entire capacity to temper and dehumidify this outdoor air. The 

new AHU should provide tempered and dehumidified (supercooled to 45°F–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 major 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 the spaces they serve while providing air filtration, heating and cooling. Another advantage at Community Rehabilitation Center is that the dedicated outdoor 

air system could be shut down during nights and weekends, when the facility is unoccupied, 

without impacting the operation of the existing AHUs. The dedicated outdoor air system 

would certainly require more capital expense and more excessive 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 shelter. Options for installing a new central 

HVAC system servicing the offices and team rooms currently using PTAC units should 

be discussed as well. A new AHU with a properly designed air distribution system would 

provide better air flow patterns through the spaces and improved filtration through the AHU, 

which would reduce the likelihood of airborne disease transmission. A new efficient central system should provide better temperature control and energy savings over the existing 

bank of PTAC units. The size and capacity of this new AHU would depend largely on the 

strategies selected to introduce outdoor air to this portion of the facility, so it is important to 

discuss both issues simultaneously.

During our visit, we noticed that Office 8 in the newer portion of the main building served 

as a medical examination room. Our measurements show (see Table 3), and ventilation fog 

testing confirmed, that this area was properly maintained under negative pressure compared 
Health Hazard Evaluation Report 2012-0263-3181 Page 11

to the corridor on the other side of the door. Thus, air from outside the exam room migrates 

into the room, instead of the other way around. This air flow pattern helps to keep any airborne infectious agents generated inside the room from traveling to the adjacent areas. 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. If it is 

ever determined that the exam room is under positive pressure to the corridor, then negative 

pressure could easily be reestablished by adjusting the ductwork so more air is exhausted 

from the exam room than is being supplied to it. 

We also inspected and tested all of the bathroom exhaust fans during our visit. In order to 

control humidity and odors, bathrooms 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. Exhaust fans were installed 

and operational in all of the bathroom areas, but the existing fans in all restrooms except the 

women’s room off the dining area were unable to maintain the spaces under negative pressure. 

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). To help maintain negative pressure in the bathrooms, the supply air 

flow to the spaces could be reduced or eliminated completely, since neither the 2010 Florida 

Building Code nor ASHRAE requires supply air flow to these spaces. Even if negative pressure can be maintained by adjusting the supply air flow, the performance of the restroom 

exhaust fans might still need to be enhanced or the fans replaced with new ones having their 

exhaust rates verified for compliance with the 2010 Florida Building Code. Bathroom fans 

should be operational whenever the rooms are occupied. [Note: The kitchen hood exhaust 

system was not evaluated at the time of the NIOSH site visit due to ongoing meal preparation 

activities, so it is 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 68.5°F–76°F in the winter, and from 75.5°F–80.5°F in the 

summer (see Table 4). The difference between the two temperature ranges is largely due to 
Page 12 Health Hazard Evaluation Report 2012-0263-3181

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. Regardless, we recommend maintaining the indoor temperature and RH levels within the ranges 

established by ASHRAE to provide the most comfortable environment to clients at Community Rehabilitation Center. Consistently 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 facility, as explained above. 

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 
Health Hazard Evaluation Report 2012-0263-3181 Page 13

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

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

$200.00. When paired with a trained and competent fit test administrator (see 29 CFR 

1910.134), these kits would allow cost-effective, on-site fit testing annually. 

Conclusions 

Since the increase in cases of TB disease in 2010, Community Rehabilitation Center has 

taken significant steps to improve the administrative controls at the facility. Important lines 

of communication between the facility and DCHD have been established, and improvements 

to staff training and awareness of TB symptoms have been made. Helping to identify clients displaying symptoms of TB disease or those listed on the DCHD target screening lists 

will help further reduce the potential for future cases of TB disease and bring the ongoing 

outbreak under control. Having consistent protective strategies upon suspect case identification is also important. While enhanced administrative controls are now in place, there is no 

written ICP established at the facility, and Community Rehabilitation Center administrators 

are encouraged to promptly coordinate with DCHD and the Florida Department of Health to 

establish one. 

From an environmental control perspective, the three central AHUs installed in the main 

building and the AHUs in both trailers were well maintained and appeared to be functioning 

properly. The Drop Off AHU seemed to function properly, but we were unable to visually 

inspect the unit during our visit. Filters with a MERV 8 efficiency value are used in all of 

the main building AHUs, and the filters were reportedly changed every 6 weeks. Filtration 

efficiency for the trailer AHUs could not be determined. The spaces down the longest hallway in the old portion of the main building were ventilated with under-window PTAC units, 

and some of the units were not functional during our visit. The preventive maintenance program in place is managed by the current facilities manager. Aside from issues with some of 

the PTAC units, the program seems to be effective although it had not been formalized into a 

written preventive maintenance or O&M plan for the facility AHUs. 

None of the AHUs at Community Rehabilitation Center were providing fresh outdoor air to 

the occupied spaces, as required by the 2010 Florida Building Code and ASHRAE guidelines. Given the number of clients served by the facility and the close proximity of clients 

to one another in some 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 some simple adjustments to AHU-3 

and all three trailer AHUs, and with more extensive modifications to AHU-1, AHU-2, and 

the Drop Off AHU, the existing equipment might be made to provide the necessary outdoor 

air. Another alternative would be to augment the existing AHUs with the installation of new 

dedicated outdoor air systems to provide outdoor air. A knowledgeable HVAC engineer 

should be consulted to discuss options for introducing outdoor air to the shelter. During 

those discussions, options for replacing the PTAC units in the old portion of the main building with a new, efficient central AHU should be investigated. Once these changes have been 
Page 14 Health Hazard Evaluation Report 2012-0263-3181

implemented, other ventilation equipment and/or supplemental ultraviolet germicidal irradiation systems could be investigated if additional environmental controls are desired.

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 facility. Having this program in place will provide 

additional protection to Community Rehabilitation Center staff working in close proximity to 

clients with suspected TB or other airborne diseases. Any respirator use at the facility should 

be covered by an OSHA-mandated respiratory protection program.

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

TB transmission at Community Rehabilitation Center. However, the ventilation systems 

clearly 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 facility. The 

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

Community Rehabilitation Center, with specific emphasis on improvements to the existing 

environmental controls so they meet all applicable standards and guidelines.

Recommendations 

Based on our assessment of environmental controls at Community Rehabilitation Center, we 

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

1. Continue to improve and enhance the TB administrative controls at the facility 

and develop a written Infection Control Plan.

● Continue working with the DCHD to screen facility staff and guests for TB 

disease.

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

or confirmed case of TB disease.

● Continue educating facility staff 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 clients.

● 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:
Health Hazard Evaluation Report 2012-0263-3181 Page 15

○ 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

○ The improved administrative controls put in place at Community 

Rehabilitation Center since the beginning of the TB outbreak

○ Input from ventilation staff. 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 facility. 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, and CDC guidelines to select the best option for 

Community Rehabilitation Center.

● Install a new, efficient central AHU to replace all existing PTAC units 

used in spaces down the longest hallway of the older portion of the main 

building. Sizing and selection of this new AHU should be done at the same 

time decisions are made on the best method to introduce outdoor air into the 

facility. 

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. 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 

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 
Page 16 Health Hazard Evaluation Report 2012-0263-3181

program needs to include:

○ Respirator types and proper respirator selection

○ Required medical evaluations for employees prior to respirator use

○ Procedures for initial and annual respirator fit testing

○ Instructions for proper respirator use

○ Information on appropriate respirator maintenance and care

○ Initial and yearly training requirements for respirator users 

○ Procedures for evaluating the effectiveness of the respiratory 

protection program

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

workplace conditions that affect respirator use.

5. Ensure all bathrooms are maintained under negative pressure and exhaust fans 

meet required performance specifications. Bathrooms currently under positive 

pressure could be brought under negative pressure by reducing or eliminating the 

supply air flow to the spaces. Even if negative pressure can be maintained by 

adjusting the supply air flow, the performance of the bathroom exhaust should still 

comply with the 2010 Florida Building Code and ASHRAE requirements. Ensure that 

all exhaust air from bathrooms 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.

6. 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, etc.) and identify personnel 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
Health Hazard Evaluation Report 2012-0263-3181 Page 17

Outline of Future NIOSH Involvement

This report will serve to close out NIOSH Technical Assistance at Community Rehabilitation Center. However, we understand that the work outlined in the recommendations above 

will take several months to complete and will represent a significant investment of time and 

financial resources. As the work proceeds, NIOSH could assist by:

● Reviewing 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

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

● 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 18 Health Hazard Evaluation Report 2012-0263-3181

References

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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.

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.

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.

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.

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.

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

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

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63(20):1720-1725.
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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.

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

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Dis 143:257-261.

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Rep 101(5):481-485.
Page 20 Health Hazard Evaluation Report 2012-0263-3181 Table 1. General air-handling unit (AHU) information NIOSH AHU Identifier Physical Location of AHU Main Locations Served by AHUA AHU Manufac- turerB AHU Model NumberB Proper Filter Configu- ration in AHUC,D Actual Filter Configu- ration in AHUB,D AHU-1 Main Building – New Section, Mechanical Room Adjacent to Office 14 All Offices and Hall- ways of Main Build- ing – New Section Ruud RHGF-100ZK949 (4) 16 × 25 × 1 (4) 16 × 25 × 1 AHU-2 Main Building, New Section, Mechanical Room Adjacent to Office 14 Dining/Activity Ar- eas of Main Building – New Section Ruud RHGE-150ZK949 (6) 20 × 25 × 1 (6) 20 × 25 × 1 AHU-3 Rooftop of Main Building – Old Section Area 3, Offices 4-11, and Copier Room 12 of Main Building – Old Section Carrier 50TCQD12A- 2B5A0A0A0 (4) 20 × 20 × 2 (RA) & (1) 20 × 24 × 1 (OA)E (4) 20 × 20 × 2 (RA) & (1) 20 × 24 × 1 (OA)E Drop Off AHU Attic Space of Drop Off Building All Drop Off Build- ing UnknownF UnknownF UnknownF UnknownF Small Trailer AHU North End of Small Trailer All of Trailer 1 UnknownG UnknownG UnknownG HomemadeH Large Trailer AHUsI South End of Large Trailer All of Trailer 2 Eubank Manufac- turing Enterprises, Inc. W36CF10B1F00A UnknownG HomemadeH A May not represent all locations served by the AHU B Information collected during visual inspection of AHU C Information gathered from product data specific to each AHU model published by respective AHU manufacturer D Value in parenthesis represents the number of filters, dimensions are width × height × depth in units of inches E RA = Return Air; OA = Outdoor Air (outdoor air damper was completely closed on this AHU)

F Ventilation measurements were taken in the area supplied by the Drop Off AHU, but access to the AHU was not readily available during the NIOSH visit.G Labels and stickers on the Small Trailer AHU were missing or faded so they could not be read.H Rough, hand-cut, homemade filters were installed in the Small Trailer AHU and both Large Trailer AHUs.I The Large Trailer had two identical AHUs, both on the south end of the trailer. 

Tables
Health Hazard Evaluation Report 2012-0263-3181 Page 21 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 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 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 — 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 anticipated, 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.
Page 22 Health Hazard Evaluation Report 2012-0263-3181 Table 3. Ventilation observations, occupant densities, and recommended outdoor air flow for areas served by central AHUs or where guests congregate SpaceA AHU Serving Space Return Flow from Space (cfm)B Supply Flow into Space (cfm)B Approximate Area of Space (ft2)C Typical Oc- cupants in SpaceD Occupant Density (#/1000 ft2)D,E,F Recommended Outdoor Air Flow (cfm)B,G Main Building – New Section Reception AHU-1 170 360 315 1 3 23.9 Conference Room AHU-1 140 85 205 6 29 42.3 Office 1 AHU-1 0 80 110 1 *9 11.6 Office 2 AHU-1 85 50 110 1 *9 11.6 Office 3 AHU-1 75 70 110 1 *9 11.6 Office 4 AHU-1 85 85 110 1 *9 11.6 Office 5 AHU-1 80 0 110 1 *9 11.6 Office 6 AHU-1 110 120 185 1 5 16.1 Office 7 AHU-1 90 110 245 1 4 19.7 Office 8 (Medical)H AHU-1 130H 90H 170 2 *12 20.2 Office 9 AHU-1 70 80 125 2 *16 17.5 Office 10 AHU-1 65 65 130 1 *8 12.8 Office 11 AHU-1 90 80 130 1 *8 12.8 Office 12 AHU-1 70 90 145 1 *7 13.7 Office 13 AHU-1 NoneI 140 160 1 *6 14.6 Men’s Room (Just Outside Dining Area) AHU-1 145J 150 220 N/AK N/AK N/AK Office 14 (Executive Director) AHU-1 210 110 200 1 5 17.0 Network/IT Administration AHU-1 90J 55 105 1 10 11.3 Restroom Adjacent to Office 14 AHU-1 40J 70 55 N/AK N/AK N/AK Dining/Activity Area (NE Half, Off Hallway 1) AHU-2 1670 1410 1440 60 42 386.4/709.2L Dining/Activity Area (SW Half, Off Hallway 2) AHU-2 1550 1315 1650 60 36 399.0/747.0L Women’s Room (Inside Dining Area) AHU-2 200J 155 220 N/AK N/AK N/AK Kitchen AHU-2 NoneI,M 905 375 4 11 75
Health Hazard Evaluation Report 2012-0263-3181 Page 23 Table 3 (continued). Ventilation observations, occupant densities, and recommended outdoor air flow for areas served by central AHUs or where guests congregate SpaceA AHU Serving Space Return Flow from Space (cfm)B Supply Flow into Space (cfm)B Approximate Area of Space (ft2)C Typical Oc- cupants in SpaceD Occupant Density (#/1000 ft2)D,E,F Recommended Outdoor Air Flow (cfm)B,G Main Building – Old Section Area 3 AHU-3 CNMN 170 280 0 0 33.6 Office 4 AHU-3 CNMN 190 120 1 *8 12.2 Office 5 AHU-3 CNMN 200 130 1 *8 12.8 Office 6 AHU-3 CNMN 190 115 1 *9 11.9 Office 7 AHU-3 CNMN 270 120 1 *8 12.2 Office 8 AHU-3 CNMN 200 105 1 *10 11.3 Office 9 AHU-3 CNMN ObsO 375 1 3 27.5 Office 10 AHU-3 CNMN ObsO 160 1 *6 14.6 Office 11 AHU-3 CNMN 180 135 1 *7 13.1 Copier Room 12 AHU-3 CNMN 300 230 1 4 18.8 Unnumbered Office Off Copier Room 12 AHU-3 145P 90 185 1 5 16.1 Office 13 AHU-3 CNMN 160 155 1 *6 14.3 Team Room 18 PTACQ ---Q ---Q 190 15 *79 86.4 Team Room 19 PTACQ ---Q ---Q 190 15 *79 86.4 Team Room 20 PTACQ ---Q ---Q 190 15 *79 86.4 Team Room 21 PTACQ ---Q ---Q 190 15 *79 86.4 Team Room 22 PTACQ ---Q ---Q 190 15 *79 86.4 Team Room 23 PTACQ ---Q ---Q 190 15 *79 86.4 Team Room 24 PTACQ ---Q ---Q 190 15 *79 86.4
Page 24 Health Hazard Evaluation Report 2012-0263-3181 Table 3 (continued). Ventilation observations, occupant densities, and recommended outdoor air flow for areas served by central AHUs or where guests congregate SpaceA AHU Serving Space Return Flow from Space (cfm)B Supply Flow into Space (cfm)B Approximate Area of Space (ft2)C Typical Oc- cupants in SpaceD Occupant Density (#/1000 ft2)D,E,F Recommended Outdoor Air Flow (cfm)B,G Drop-Off Building Game/Activity Area Drop Off AHU 415 370 485 30 62 179.1 Small Trailer Adult Basic Education Area Small Trailer AHU 145 210 335 4 12 40.1 Storage Room Small Trailer AHU 70 305 130 0 0 15.6 Office Area Small Trailer AHU 40 360 130 1 *8 12.8 Large Trailer Office 1 Large Trailer AHUs WallR 160 115 1 *9 11.9 Office 2 Large Trailer AHUs WallR 110 115 1 *9 11.9 Waiting Area Large Trailer AHUs NoneI 70 185 1 5 16.1 Office 3 Large Trailer AHUs WallR 80 90 1 *11 10.4 Office 4 Large Trailer AHUs WallR 60 85 1 *12 10.1 Office 5 Large Trailer AHUs WallR 95 110 1 *9 11.6 Restroom Large Trailer AHUs 30J 115 65 N/AK N/AK N/AK Office 6 Large Trailer AHUs WallR 100 95 1 *11 10.7 Back Reception Area Large Trailer AHUs WallR 40 130 1 *8 12.8 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 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.
Health Hazard Evaluation Report 2012-0263-3181 Page 25 H 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). This space was under negative pressure during the NIOSH visit. I There was/were no return grille(s) in this space. Only supply vent(s) was/were present. J This area was equipped with a switch activated exhaust fan designed for intermittent use when the space is occupied. K N/A = not applicable. Neither ASHRAE Standard 62.1-2010 nor the 2010 Florida Building Code include outdoor air recommendations for restrooms and bathrooms. 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. Bathroom 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. L 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). M Does not include air pulled from the area by kitchen exhaust hoods. Air flow measurements through exhaust hoods were not taken. N CNM = could not measure. Return air passed around light fixtures into the plenum space above the drop ceiling. Measurements of the return air could not be taken accurately during the NIOSH visit. O Obs = obstructed. Air flow measurements could not be taken because the supply vents were obstructed by furniture, storage boxes, shelves, etc. P This was an unducted return grille through the drop ceiling into the ceiling plenum. Q These areas were ventilated by packaged terminal air conditioner (PTAC) units that did not provide outdoor air to the spaces and are not part of the central ventilation system. No supply or return measurements were taken. R Return air from these spaces flowed through grilles in the walls into other occupied spaces until finally returning to the AHUs on the end of the trailer. No measurements of this return air were taken.
Page 26 Health Hazard Evaluation Report 2012-0263-3181

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

 Society of Heating, Refrigerating and Air-Conditioning Engineers, 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 2012-0263-3181 Page 27

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Page 28 Health Hazard Evaluation Report 2012-0263-3181

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 Community Rehabilitation 

Center, 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/2012-0263-3181.pdf.

Recommended citation for this report:

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

environmental controls at social assistance facility (Community 

Rehabilitation Center) 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. 2012-0263-3181.
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