Evaluation of Exposure 

to Tuberculosis Among 

Employees at a 

Medical Center — 

Arizona

Marie A. de Perio, MD

R. Todd Niemeier, MS, CIH

Health Hazard Evaluation Report

HETA 2011-0137-3159

April 2012

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

Workplace

Safety and Health

 National Institute for Occupational 

Safety and Health
The employer shall post a copy of this report 

for a period of 30 calendar days at or near 

the workplace(s) of affected employees. The 

employer shall take steps to insure that the 

posted determinations are not altered, defaced, 

or covered by other material during such 

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

amended at 45 FR 2653, January 14, 1980].
Health Hazard Evaluation Report 2011-0137-3159 Page i

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

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

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

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

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

Results..............................................................................................................6

Discussion.................................................................................................... 18

Conclusions................................................................................................. 22

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

References.................................................................................................... 28

Contents

Acknowledgments Acknowledgments and Availability of Report................................ 35

Appendix Ventilation Measurements..................................................................... 30
Page ii Health Hazard Evaluation Report 2011-0137-3159

Abbreviations

ACH Air changes per hour

ACU Adult care unit

AFB Acid fast bacilli

AII Airborne infection isolation

CDC Centers for Disease Control and Prevention

CFM Cubic feet per minute

CFR Code of Federal Regulations

ED Emergency department

HEPA High-efficiency particulate air

HHE Health hazard evaluation

HVAC Heating, ventilating, and air-conditioning

ICP Infection control practitioner

ICU Intensive care unit

NA Not applicable

NAICS North American Industry Classification System

NIOSH National Institute for Occupational Safety and Health

OSHA Occupational Safety and Health Administration

PAPR Powered air purifying respirator

PPE Personal protective equipment

TB Tuberculosis

TST Tuberculin skin test 
Health Hazard Evaluation Report 2011-0137-3159 Page iii

The National Institute for 

Occupational Safety and 

Health (NIOSH) received a 

health hazard evaluation 

request from management 

representatives at 

a medical center in 

Arizona. The request 

was submitted because 

of concerns about 

exposure of employees 

to Mycobacterium 

tuberculosis.

Highlights of the

NIOSH Health

Hazard Evaluation

What NIOSH Did

● We visited the medical center in August 2011.

● We reviewed the policies and practices related to 

tuberculosis (TB).

● We measured ventilation airflow in airborne infection 

isolation (AII) rooms and anterooms.

● We interviewed 39 hospital employees. We also reviewed 

relevant medical records.

● We looked for factors associated with having a new positive 

tuberculin skin test (TST).

● We observed the respirator fit testing of two employees.

What NIOSH Found

● Eighteen employees had a new positive TST in 2011.

● One employee was diagnosed with active TB in 2011.

● Hospital transmission of TB to employees was likely.

● Seven AII rooms were not functioning properly.

● Working as a certified nursing assistant was associated with 

having a new positive TST.

● The respiratory protection program and employee training 

and screening need to be improved.

What Managers Can Do

● Provide annual TB training to all employees. Offer this 

training during work hours.

● Place signs about AII precautions outside patients’ rooms as 

soon as active TB is suspected.

● Enforce the TB screening of employees.

● Do not use the seven malfunctioning AII rooms until they 

are repaired.

● Rebalance the heating, ventilating, and air-conditioning 

systems in AII rooms and adjacent anterooms. Ensure that 

they have the proper number of air changes per hour and 

have airflow in the proper direction.

● Improve the procedures for fit testing respirators.
Page iv Health Hazard Evaluation Report 2011-0137-3159

Highlights of the

NIOSH Health

Hazard Evaluation

 (continued)

 

What Employees Can Do

● Get a TST every year if you had a negative TST in the past.

● Get a medical evaluation for TB every year if you had a 

positive TST in the past.

● Recognize TB symptoms, report these to the nursing 

supervisor and caring physician, and promptly place patients 

with these symptoms in AII rooms.

● Close the doors between anterooms and adjacent hallways 

when housing active TB patients.

● Test the negative pressure of airflow in AII rooms when used 

for patients in isolation.

● Wear the appropriate respiratory protection when you are in 

contact with a patient with known or suspected active TB.
Health Hazard Evaluation Report 2011-0137-3159 Page v

NIOSH investigators 

examined the recent 

incidence of active TB and 

latent TB infection among 

employees at a medical 

center. Investigators 

also assessed the TBrelated infection control 

and occupational health 

practices. Hospital 

transmission of TB 

to employees likely 

occurred in 2011. The 

investigation revealed 

gaps in implementation of 

administrative, engineering, 

and PPE controls.

Summary

In July 2011, NIOSH received an HHE request from management 

representatives at a medical center in Arizona. The request 

concerned the exposure of employees to Mycobacterium tuberculosis. 

The management representatives asked for our assistance in 

evaluating the infection control and occupational health practices 

related to TB.

During an on-site evaluation in August 2011, we reviewed the 

medical center’s TB-related occupational health and infection 

control policies and practices. We also assessed the ventilation 

in the AII rooms and sputum booth, interviewed 39 employees, 

reviewed pertinent medical records, and observed the respirator 

fit testing of two employees. We analyzed the medical center’s TB 

screening data and interview data to identify factors associated 

with having a new positive TST.

A health hazard from exposure to Mycobacterium tuberculosis

existed at this medical center. Our investigation revealed 18 

(2.3%) employees with a TST conversion in 2011; one of these 

employees was diagnosed with active TB. Most employees who 

had TST conversions worked in the hospital during the stay of 

an active TB patient who was not initially placed in AII. This 

finding suggests that hospital transmission likely occurred. 

Certified nursing assistants were significantly more likely to have 

a TST conversion than other hospital employees. Although the 

medical center’s written tuberculosis control program policy was 

comprehensive, our investigation revealed gaps in implementation 

of its administrative, engineering, and PPE controls. We found 

deficiencies in employee TB-related training and screening. Six 

AII rooms were under positive pressure, and another AII room 

had fewer than the recommended 6 ACH during our visit. 

Additionally, seven anterooms adjacent to AII rooms had fewer 

than 10 ACH.

We recommended giving TB training to all employees on hire 

and annually thereafter and considering ways to enforce the 

requirement for employee TB screening. We recommended that 

suspect TB patients be promptly placed in an AII room with 

appropriate signage indicating their status. We also recommended 

that the seven malfunctioning AII rooms not be used for that 

purpose. The HVAC systems should be rebalanced to ensure that 

all AII rooms are under negative pressure relative to adjacent 

anterooms and/or hallways, and doors between anterooms and 

adjacent hallways should be closed when active TB patients are 
Page vi Health Hazard Evaluation Report 2011-0137-3159

Keywords: NAICS 622110 (General Medical and Surgical Hospitals), 

TB, tuberculosis, infectious diseases, infection, hospital, healthcare, 

ventilation, airborne, American Indian, Native American 

Summary

 (continued) housed. Negative pressure of airflow should be tested daily in 

AII rooms used for patients in isolation. We also recommended 

improvements in respiratory protection training and in respirator 

fit-testing procedures.
Health Hazard Evaluation Report 2011-0137-3159 Page 1

Introduction

In July 2011, NIOSH received an HHE request from management 

representatives at a medical center in Arizona. The request 

concerned the exposure of employees to Mycobacterium tuberculosis. 

The management representatives asked for our assistance in 

evaluating the infection control and occupational health practices 

related to TB.

During an on-site evaluation in August 2011, we observed work 

processes, work practices, and workplace conditions. We interviewed 

employees, reviewed employee health and pertinent medical records, 

and evaluated the ventilation system in selected areas.

Tuberculosis

TB, a disease caused by the bacteria Mycobacterium tuberculosis, is 

spread from person to person through the air. TB usually infects 

the lungs, but it can also infect other body parts such as the brain, 

kidneys, or spine. The symptoms of active TB disease in any body 

part include feeling sick or weak, weight loss, fever, and night 

sweats. The symptoms of TB disease of the lungs also include 

coughing, chest pain, and coughing up blood.

TB bacteria are released into the air when a person with TB disease 

of the lungs or throat coughs, sneezes, speaks, or sings. These 

bacteria can stay in the air for several hours, depending on the 

environment. Persons who breathe air containing these TB bacteria 

can become infected.

Persons with latent TB infection have TB bacteria in their bodies, 

but they are not ill because the bacteria are not active. These 

persons do not have symptoms of TB disease, and they cannot 

spread the germs to others. They may develop TB disease in the 

future but can be treated to prevent this from happening. Persons 

with TB disease are sick from active TB bacteria when the bacteria 

are multiplying, which causes destruction of tissue in their body. 

They usually have symptoms of TB disease and are capable of 

spreading TB bacteria to others.

Background on the Acute Care Hospital

At the time of our visit, the medical center was a 73-bed healthcare 

center accredited by the Joint Commission. The medical center had 

approximately 1,000 employees. The inpatient hospital was built in 
Page 2 Health Hazard Evaluation Report 2011-0137-3159

Introduction

 (continued) 1975, and the adjacent outpatient facility was built in 2010. The 

medical center provided services to people in a 4,400-square-mile 

area on two American Indian reservations.

At the time of our visit, one nurse, known as the ICP, was 

responsible for all infection control and occupational health 

activities at the medical center. These activities also included 

employee TST screening and administration of the employee 

respiratory protection program. The medical center’s TB policy 

required annual TST testing of all employees with face-to-face 

patient contact.

Investigation by the Centers for Disease 

Control and Prevention’s Division of 

Tuberculosis Elimination

In July 2011, at the request of the American Indian tribe’s 

Division of Health, CDC’s Division of TB Elimination conducted 

an investigation to describe the epidemiology of TB on the 

reservation, including the recent occurrence of TB clusters. Part of 

that investigation focused on a healthcare-related outbreak at the 

hospital and identified three definite outbreak-related cases of TB. 

A definite outbreak-related case was defined as culture-confirmed 

TB with a TB isolate matching the outbreak genotype (PCR 

17301) diagnosed since August 1, 2010, in a person who visited, 

was hospitalized in, or worked in the medical center. Two cases 

were inpatients during their infectious periods. Patient 1, the only 

sputum AFB smear-positive case in the outbreak, was diagnosed in 

January 2011. Patient 2, a hospital employee, was diagnosed in May 

2011. This employee was a certified nursing assistant in the ED and 

was working there during Patient 1’s second admission. Patient 3, 

Patient 1’s spouse, was diagnosed in June 2011.

A contact investigation of employees initially focused on 

employees exposed to Patient 1. However, this was broadened to 

all employees, including those without direct patient contact. Most 

employees were screened in a 3-month period starting in April 

2011. For CDC’s Division of TB Elimination investigation, a TST 

conversion was defined as an employee with a new positive TST 

in 2011 who had a previous negative TST after July 12, 2010. This 

date was chosen to ensure that a TST conversion was appropriately 

attributed to Patient 1; another active TB patient was hospitalized 

around that time. Excluded employees included those who were 
Health Hazard Evaluation Report 2011-0137-3159 Page 3

Introduction

 (continued) not tested or those who had a prior positive TST, no baseline TST, 

or a baseline TST before July 12, 2010.

Of 46 employees who reported exposure to Patient 1, 19 (41%) 

were excluded. Of the remaining 27 employees, 6 (22%) had TST 

conversions, including Patient 2, the employee with active TB. Of 

the 1,087 employees who had not reported exposure to Patient 1, 

321 (30%) were excluded. Of the remaining 766, 5 (1%) had TST 

conversions. Employees exposed to Patient 1 were 34 times more 

likely than employees who were not exposed to Patient 1 to have a 

TST conversion. This finding suggested that transmission in the 

workplace was responsible for the employee conversions.

The investigation also found that delays in placing patients 

in respiratory AII contributed to this outbreak. For the 

three TB patients, the length of time in the hospital without 

isolation ranged from 7 hours to 7 days. Although all patients 

presented with respiratory symptoms, symptom recognition and 

consideration of TB as a diagnosis were delayed. Thus, respiratory 

protection was not used, placing employees at risk for TB.

To complement the CDC’s Division of TB Elimination 

investigation, management representatives at the medical center 

asked NIOSH for assistance regarding the medical center’s 

TB-related infection control and occupational health practices.
Page 4 Health Hazard Evaluation Report 2011-0137-3159

Assessment

The purpose of our evaluation was to (1) investigate the incidence 

of active TB and latent TB infection among hospital employees 

from 2009–2011; (2) assess the medical center’s TB-related 

administrative, engineering, and PPE controls; and (3) make 

recommendations to improve TB-related occupational health and 

infection control practices.

In response, we (1) reviewed the medical center’s TB-related 

occupational health and infection control policies and practices, 

(2) evaluated the ventilation in the hospital’s AII rooms and 

sputum booth, (3) held confidential medical interviews with 

employees and reviewed pertinent medical records, and (4) 

observed respirator fit testing of two employees.

Review of Tuberculosis-Related 

Occupational Health and Infection 

Control Policies and Practices

Prior to the visit, we reviewed the medical center’s tuberculosis 

control program policy, which was last revised on December 18, 

2008. We also obtained TB-related training materials for employees 

and historical employee TST screening records from 2004–2011.

Ventilation Assessment

We walked through the hospital (including the mechanical rooms) 

and on the roof to observe the ventilation system. We also reviewed 

ventilation plans with the hospital engineering staff. We measured 

the pressure difference in the doorways between the AII rooms 

and adjacent anterooms or adjacent hallways with a TSI DP-CalcTM 

micromanometer (TSI, Inc., Shoreview, Minnesota) and used smoke 

tubes to visualize airflow in the doorways. We also obtained airflow 

measurements from supply diffusers and ducted exhausts in all AII 

patient rooms, bathrooms, and adjacent anterooms to assess the 

potential for dissemination of airborne Mycobacterium tuberculosis. We 

calculated ACH using the exhaust airflow in these rooms. Airflow 

measurements were made with a TSI® Accubalance® Plus air 

capture hood (TSI, Inc., Shoreview, Minnesota). We also reviewed 

the ventilation controls and service records for the sputum booth in 

the respiratory therapy department.
Health Hazard Evaluation Report 2011-0137-3159 Page 5

Assessment

 (continued) Confidential Medical Interviews and 

Medical Record Review

We selected 42 current and former hospital employees to 

participate in individual semistructured confidential interviews. 

These employees were selected because they were reported to have 

a TST conversion since November 2009 and/or were reported to 

have had exposure to Patient 1 in January 2011. A TST conversion 

was defined as an employee with a new positive TST who had a 

previous negative baseline TST. Of these 42 employees, 22 were 

reported to have had exposure to Patient 1 in January 2011 but 

were found to have negative TSTs. The other 20 were reported to 

have had a TST conversion since November 2009; 11 of these 20 

were reported to have had exposure to Patient 1 in January 2011. 

During these interviews, we discussed their knowledge about TB 

and TB-related medical center procedures, their known exposures 

to TB, their respiratory protection practices, and other related 

concerns they had. We supplemented the information gathered 

from these interviews with information from employee health and 

other pertinent medical records.

We described characteristics of the employees who had TST 

conversions in 2011. We then further analyzed those employees 

who were documented as working in the ACU, ICU, or ED while 

Patient 1 was not in AII. We compared those employees with a 

TST conversion in 2011 to those employees who did not have a 

TST conversion to determine factors associated with conversion. 

We conducted bivariate analysis with SAS 9.2 (SAS Institute, Cary, 

North Carolina). All statistical tests were 2-tailed, with a P value of 

less than 0.05 considered statistically significant.

Observation of a Respirator Fit-testing 

Session

We observed a qualitative respirator fit-testing session in which two 

employees were fit tested at the hospital. We listened to fit-testing 

instructions given to employees being fit tested and noted specific 

procedures used for qualitatively fit testing the respirators.
Page 6 Health Hazard Evaluation Report 2011-0137-3159

Results

Review of Tuberculosis-Related 

Occupational Health and Infection Control 

Policies and Practices

As stated in the medical center’s tuberculosis control program policy, 

the key program personnel are a TB control officer and a TB technician. 

The TB control officer is responsible for following active TB cases, 

providing consultation to the medical staff, supervising the chest clinic, 

keeping current with treatment and other related developments in TB, 

and providing in-service training and community education as needed. 

The TB technician is appointed and supervised by the tribe’s TB control 

program and is not a hospital employee. The TB technician provides 

guidance and assistance to the medical center and is responsible for 

community contact investigations. The technician also assists with TST 

testing of hospital employees. The TB technician position had not been 

continuously filled for close to 2 years. TB technicians from surrounding 

service units were intermittently staffing this position while continuing 

to staff their own service unit. At the time of our evaluation, a TB 

technician and a public health nurse were working together on the TB 

contact investigations.

The ICP was responsible for all infection control and occupational 

health activities at the medical center at the time of our visit. These 

activities also included employee TST screening and administration of 

the employee respiratory protection program.

Tuberculosis Screening Program

TST testing of all new employees was required on hire, and twostep testing was performed if more than a year had elapsed since the 

employee’s last test. Exceptions included employees with a TST within 

the past 3 months, a previously positive TST, or an allergy to the test 

components. Employees with previously positive TSTs or an allergy were 

required to have a chest x-ray.

Annual TST testing of all employees with face-to-face patient contact 

was required. Testing was optional for employees without face-to-face 

patient contact until the spring of 2011, when the outbreak occurred. 

Test results, including conversion rates, were logged and reviewed by the 

employee health clinic, TB control program, and the ICP. Employees 

who converted were evaluated clinically, offered therapy for latent TB 

infection, and followed by the medical center’s chest clinic. Employees 

with previous positive TST results did not undergo further TST testing, 

but had an annual symptom evaluation.
Health Hazard Evaluation Report 2011-0137-3159 Page 7

Results

 (continued) From 2004–2006, the TST screening program did not distinguish 

between employees with and without face-to-face patient contact; 

screening was required for all employees. Beginning in 2007, the 

program did make this distinction as described above. Annual 

compliance percentages for TST screening from 2004–2011 are shown 

in Figure 1. Of those employees with previously negative TST results, 

annual compliance percentages for TST screening fluctuated from 

56%–94% from 2004–2011. From 2007–2011 when the program 

distinguished between employees with and without face-to-face patient 

contact, annual compliance rates for TST screening fluctuated from 

71%–94% for employees with face-to-face patient contact and 34%–

93% for employees without face-to-face patient contact. The 2011 

numbers were as of mid-August 2011.

Figure 1. Annual compliance percentages for TST screening among employees with a previously negative TST.

*Note that the percentages for 2011 were as of mid-August 2011.

The annual percentages of employees who had a TST placed but 

did not return for reading ranged from 0%–16% between 2004 

and 2011 (Figure 2). The year 2010 had the highest percentage of 

employees who did not return for reading at 16%.
Page 8 Health Hazard Evaluation Report 2011-0137-3159

Figure 2. Annual percentages of employees who had a TST placed but did not return for reading. 

*Note that the percentages for 2011 were as of mid-August 2011.

Annual percentages of employees tested who had new positive 

TSTs ranged from 0%–2.3% for all employees from 2004–2011 

(Figure 3). From 2007–2011, annual percentages of employees with 

new positive TSTs ranged from 0.2%–3.6% for employees with 

face-to-face patient contact and 0%–0.9% for employees without 

face-to-face patient contact. Again, the 2011 numbers were as of 

mid-August 2011. The percentage of employees with new positive 

TSTs was higher for those without face-to-face patient contact 

than for those with face-to-face patient contact during 2008 

(0.8% vs. 0.2%) and 2009 (0.9% vs. 0.4%). The year 2011 saw a 

significant increase in the percentage of employees with face-to-face 

patient contact with new positive TSTs though the percentage of 

employees without face-to-face patient contact remained stable.

Results

 (continued)
Health Hazard Evaluation Report 2011-0137-3159 Page 9

Results

 (continued)

Figure 3. Annual percentages of employees tested with new positive TSTs.

*Note that the percentages for 2011 were as of mid-August 2011.

Respiratory Protection Program

At the time of our HHE, the employee respiratory protection 

program was administered by the ICP. This program was a 

component of the medical center’s tuberculosis control program 

policy. The program contained all of the basic elements required 

by the OSHA respiratory protection standard, including respirator 

selection, medical evaluation, respirator training, fit testing, 

respirator use, and handling of disposable respirators [29 CFR 

1910.134].

The medical center’s written fit-testing procedures included all the 

elements required by the OSHA respiratory protection standard 

[29 CFR 1910.134]. The program required medical clearance prior 

to fit testing. Employees were required to complete a medical 

questionnaire, which contained all of the questions in the OSHA 

Respirator Medical Evaluation Questionnaire, Appendix C, to the 

OSHA respiratory protection standard [29 CFR 1910.134].
Page 10 Health Hazard Evaluation Report 2011-0137-3159

Results

 (continued) The hospital stocked four N95 filtering facepiece respirators. These 

included the 3MTM1860 (small and regular sizes), 3MTM 1870 

regular size, and Kimberly Clark PFR95 models, all of which were 

NIOSH-approved (Figures 4–6).

Additionally, the hospital stocked loose-fitting PAPRs (MAXAIR® 

cuff system by Bio-Medical Devices Intl.) (Figure 7). Units were 

pre-assembled in Sterile Processing and were available in the ACU, 

ICU, walk-in clinic, radiology, ED, sterile processing, and the 

infection control/employee health office. Employees were trained 

annually on use and care of the PAPRs. After each training session, 

they took a quiz, which was filed in their employee health record.

Ventilation Assessment

At the time of our visit, the hospital maintained 18 AII rooms, 

including eight rooms each in the ACU (Q8, Q9, Q10, Q11, Q12, 

Q17, Q18, Q19) and pediatric unit (R9, R11, R12, R14, R21, R23, 

R24, R26), and one room each in the ICU and ED. The AII rooms 

were often used as standard patient rooms as well. All AII rooms in 

the ACU had dedicated anterooms, which served as the only path 

in and out of the AII rooms. In the pediatric unit, one anteroom 

served a set of two AII rooms. The AII rooms in the pediatric 

unit also had additional doors directly between the AII rooms 

and adjacent hallways allowing healthcare personnel to bypass 

the anteroom to enter the patient room. We were told that when 

patients with airborne infectious diseases were placed in these AII 

rooms, the doorway between the hallway and AII room was kept 

shut, and hospital staff entered and exited the AII room via the 

anteroom doorway. The ICU AII room had an anteroom and a 

doorway between the AII room and adjacent ICU suite (similar to 

the pediatric AII room design). The ED AII room opened directly 

to the ED (i.e., it had no anteroom).

The HVAC systems serving the isolation rooms were installed 

approximately 12 years ago. They were constant air volume systems, 

meaning that the airflow rate in these areas remained steady 

throughout the day, but the air temperature varied depending on 

the thermostat set points. The AII rooms in the hospital had single 

pass ventilation; all air was directly exhausted to the outside on the 

roof of the hospital via ducts. These rooftop exhausts were located 

more than 25 feet away from any outdoor air intakes and were 

appropriately labeled. The hospital engineering staff reported that 

Figure 4. The 3M 1860 N95 respirator 

in the regular size stocked by the 

hospital. Photo © 2011 3M Company. 

All rights reserved.

Figure 5. The 3M 1870 respirator 

stocked by the hospital. Photo © 2011 

3M Company. All rights reserved.

Figure 6. The Kimberly-Clark PFR95 

respirator stocked by the hospital. 

Photo © 2006 Kimberly-Clark 

Worldwide, Inc. All rights reserved.
Health Hazard Evaluation Report 2011-0137-3159 Page 11

Results

 (continued)

the HVAC supply ducts delivered approximately 10% of outdoor 

air in the summer and up to 100% outdoor air in the winter, 

depending on the outdoor temperature.

Electronic door pressure monitors with low pressure alarms 

monitored the pressure between AII rooms and adjacent hallways. 

All AII rooms were fitted with an electronic door pressure monitor 

except for the AII room in the ED. These room pressure monitors 

allowed staff to change damper settings on ducted air returns in the 

AII rooms, which changed the rooms between negative pressure 

and positive pressure. In some AII rooms, we had to change the 

settings from positive pressure to negative pressure before making 

airflow measurements. Additional settings allowed users to reverse 

the current damper setting on the ducted exhausts. This control 

setting is independent of the positive and negative pressure 

settings, allowing users to reverse the damper setting in the ducted 

exhausts from open to closed or vice versa. Some of the electronic 

door pressure monitors did not alarm when the AII rooms were 

not under appropriate negative pressure. Hospital engineering 

staff reported that these electronic pressure monitors had not 

been calibrated since they were installed approximately 12 years 

ago. Many of the relative pressure readings on the electronic door 

monitors were much different than the readings we observed with 

our calibrated micromanometer (Table A1).

The results of pressure measurements for AII rooms are presented 

in the Appendix. When the electronic sensors were placed in 

the negative pressure mode, six AII rooms were under positive 

or neutral pressure relative to the anterooms and/or hallways. 

These included rooms Q8, Q11, Q12, Q17, R11, and R21. All of 

the other AII rooms in the ACU (R9, R12, R14, R23, R24, R26), 

pediatric unit (Q9, Q10, Q18, Q19), and the AII room in the ED 

(ED6) were under negative pressure relative to adjacent areas. The 

ICU AII room was under slight positive pressure relative to the 

adjacent anteroom when the exhaust fan in the anteroom was 

turned on. When this exhaust fan was turned off, the ICU AII 

room was under negative pressure relative to both the adjacent 

anteroom and main ICU area. In AII rooms that were under 

negative pressure relative to adjacent anterooms and hallways, 

pressure measurements ranged from –0.0040 to –0.0265 inches of 

water gauge.

Figure 7. The MAXAIR® cuff system, 

a PAPR system, stocked by the 

hospital. Photo © 2004–2010 BioMedical Devices International. All rights 

reserved.
Page 12 Health Hazard Evaluation Report 2011-0137-3159

Results

 (continued) The airflow measurements and calculated ACH rates for AIIs and 

anterooms are also found in the Appendix. The airflow values are 

presented as an average of three measurements. All but 

one of the AII rooms under negative pressure relative to adjacent 

anterooms or hallways had more than 6 ACH based on the amount 

of air exhausted from the patient room (note: ACH calculations 

did not include exhaust measurements from adjacent patient room 

bathrooms). Rooms with more than 6 ACH included R12, R14, R23, 

R24, R26, Q9, Q10, Q18, Q19, ER6, and the ICU AII rooms. AII 

room R9 was calculated to have 5.7 ACH. Airflow measurements 

were collected in the 13 anterooms that served the AII rooms. The 

calculated ACH, on the basis of exhaust airflow in these anterooms, 

ranged from 0–33.6 ACH. Seven of the thirteen anterooms (R9/R11, 

R21/R23, R24/R26, Q8, Q9, Q12, and Q19) provided fewer than 

10 ACH. When AII rooms were occupied by patients with potentially 

airborne infectious diseases, hospital staff kept the door between the 

AII rooms and anterooms closed. However, it was noted that the 

hospital staff usually did not close the door between the anterooms 

and hallways. Hospital managers indicated that closing this door made 

it difficult to observe patients in AII rooms.

An Emerson 7-AT sputum induction chamber sputum booth in the 

respiratory therapy department was used to collect sputum samples 

from suspected TB patients approximately three to four times per year. 

According to the manufacturer, the chamber supplied a variable airflow 

rate from 150 to 270 CFM, which is equivalent to a rate of 250 to 460 

ACH. Air was drawn into the booth via an inlet with a pre-filter on the 

top of the booth. Air was passed through a large filter on the back of 

the booth and exhausted back into the room. Internal alarms indicated 

when the blower malfunctioned, when leaks in the chamber occurred, 

or when filters needed changing. We were unable to access the exhaust 

air filter to determine the type of filter present. Using smoke, we 

determined that air was flowing in the correct direction (i.e., exhausted 

through a large filter on the back of the unit). The unit was serviced 

twice per year by a contractor according to manufacturer specifications 

and documented in service records. The unit was last serviced in 

February 2011; it was scheduled for service again in August 2011.

Confidential Medical Interviews and 

Medical Record Review 

Of the 42 employees selected for interviews, 39 employees (93%) 

participated by phone or in person; we were unable to reach three 
Health Hazard Evaluation Report 2011-0137-3159 Page 13

Results

 (continued) employees. These 39 employees included 19 (95%) of 20 employees 

reported to have had a TST conversion since November 2009 and 

20 (91%) of 22 employees who were reported to have had exposure 

to Patient 1 when that patient was not in AII in January 2011 

but were found to have a negative TST. We reviewed employee 

health clinic records and other pertinent medical records for 

all 20 employees reported to have had a TST conversion since 

November 2009.

For the 40 employees who completed interviews and/or who had 

medical records reviewed, the median age was 37 years, with a 

range of 22 to 63 years. Thirty-three (82%) were female; 18 (45%) 

were American Indian, 17 (42%) were white, 2 (5%) were Asian 

American, and 2 (5%) considered themselves an “other” race.

Thirty-nine (98%) of the 40 employees had face-to-face contact with 

patients during their work. The median amount of time the 39 

interviewed employees reported working at the hospital was 2 years, 

with a range of 9 months to 32 years. Other work characteristics 

are shown in Table 1.

Table 1. Work characteristics of employees who completed interviews and/or who had medical records reviewed

Work Characteristic No. (%) Employees

n = 40

Job title

 Registered nurse 17 (42)

 Certified nursing assistant 10 (25)

 Physician 4 (10)

 Medical support assistant 6 (15)

 Other 3 (8)

Primary department

 Adult care unit 24 (60)

 Emergency department 7 (18)

 Patient registration 2 (5)

 Intensive care unit 2 (5)

 Other 5 (12)

Eight (21%) of the 39 interviewed employees reported having 

attended general TB training during their employment at the 

hospital. Thirty-one (79%) correctly identified at least two 

symptoms of active TB, but some employees did not know the 

difference between latent and active TB. We also heard various 
Page 14 Health Hazard Evaluation Report 2011-0137-3159

Results

 (continued) answers on procedures for a patient suspected of having active TB 

and for an employee exposed to a patient with active TB. Thirtyseven (95%) of the 39 interviewed employees reported having 

annual TSTs prior to our visit.

Regarding respiratory protection, 37 (95%) of the 39 interviewed 

employees reported having access to an N95 respirator or PAPR 

during their employment at the hospital though some reported that 

N95 respirators were difficult to find. Thirty (77%) reported having 

undergone respirator training since they started work at the hospital, 

with most reporting that they had undergone training on use of the 

PAPRs and not the N95 respirators. Twenty-five (64%) reported 

that they had respirator fit testing since starting work at the hospital, 

and 23 reported being successfully fitted. Although some employees 

reported fit testing within the past year, others had not been fit 

tested in 10 years. Nineteen reported knowing what respirator they 

were fitted for either by model or by description. Twelve (31%) 

reported ever wearing another respirator they had not been fitted for 

during their employment.

Of the 31 employees reporting contact with any patient suspected or 

known to have active TB disease, 27 (87%) reported always wearing 

a fit-tested N95 respirator or PAPR, 3 (10%) reported sometimes 

wearing either, and 1 (3%) reported never wearing either.

Employee with Healthcare Associated Active 

Tuberculosis

When diagnosed on May 11, 2011, the employee with active TB was 

working as a certified nursing assistant in the hospital’s ED. The 

employee had no pertinent medical history that increased the risk of 

the employee for active TB and was diagnosed after multiple ED 

presentations for cough and shortness of breath beginning March 

8, 2011. The employee was treated with antibiotics and steroids for 

presumptive pneumonia. The employee again sought medical care 

and was hospitalized on April 20, 2011. The employee’s sputum 

AFB smear was negative on April 20, 2011, and the culture became 

positive for Mycobacterium tuberculosis on May 11, 2011, after the 

hospital discharge. The employee was readmitted to an AII room in 

the hospital, started on a standard 4-drug TB regimen, discharged, 

and was receiving directly observed therapy at the time of our visit. 

Though the employee initially reported no known history of working 

with patients with active TB disease, a review of the ED shift records 

found that the employee was working during a January 24, 2011, ED 

shift when Patient 1 was evaluated without being placed in AII.
Health Hazard Evaluation Report 2011-0137-3159 Page 15

Results

 (continued) Employees with a Tuberculin Skin Test 

Conversion in 2011

We excluded one of the 19 employees reported to have a TST 

conversion in 2011 from subsequent analysis. This employee, who 

was a new hire within the last year, reported a previous negative 

baseline TST, but this negative result was not documented.

The median age of the 18 employees with documented TST 

conversion in 2011 was 40 years, with a range of 22 to 63 years. 

Fifteen (83%) were female. Eleven (61%) were American Indian, 

five (28%) were white, 1 (6%) was Asian American, and one (6%) 

was an “other” race.

Their job titles included certified nursing assistant (n = 7), medical 

support assistant (n = 4), registered nurse (n = 3), physician (n = 3), 

and other (n = 1). Primary departments worked included ACU (n 

= 9), patient registration (n = 2), ED (n = 2), and ICU (n = 1). The 

other four worked in various locations. Seventeen (94%) of the 18 

employees reported having face-to-face contact with patients during 

their job.

Fourteen (82%) of the 17 interviewed employees with TST 

conversions reported having face-to-face contact with a patient 

known to have active TB in the prior past year. None of the 17 

interviewed employees reported having face-to-face contact with 

anyone in their household or community known to have active TB, 

and three reported having face-to-face contact with someone else 

known to have active TB (such as a coworker). Ten (56%) of the 

18 employees with TST conversions were documented in hospital 

records as having worked in the hospital during Patient 1’s stay 

when that patient was not in AII. Two (11%) of the 18 employees 

with TST conversions had no known face-to-face contact with 

anyone known to have active TB.

Four (22%) of the 18 employees with TST conversions had an 

underlying medical condition that put them at greater risk of 

progression to active TB. Seventeen (94%) employees with TST 

conversions had undergone medical evaluation for their TST 

conversion at the time of the interviews. The other one was waiting 

to be seen. Twelve of these 17 employees were seen in the medical 

center’s chest clinic. Of the 16 employees diagnosed with latent TB 

infection and who had undergone a medical evaluation, all were 

offered treatment with isoniazid. Thirteen (81%) started treatment 

with isoniazid, and 2 (15%) of 13 had prematurely discontinued 

treatment by the time of the interviews.
Page 16 Health Hazard Evaluation Report 2011-0137-3159

Results

 (continued) Characteristics Associated with Tuberculin 

Skin Test Conversion

We compared characteristics of 8 non-physician employees with a 

TST conversion in 2011 and 17 non-physician employees without a 

TST conversion, all of whom were documented to have worked in 

the ACU, the ICU, or the ED while Patient 1 was not in AII. We 

excluded physicians from the analysis because we were not able to 

obtain staffing records for all physicians working while Patient 1 

was not in AII.

Age and the number of years worked at the hospital were not 

significantly associated with TST conversion. However, working as 

a certified nursing assistant was significantly associated with having 

a TST conversion (75% vs. 18%, P = 0.01). Additional results of 

this analysis are shown in Table 2. No other risk factors for TST 

conversion were identified.

Table 2. Characteristics associated with having a tuberculin skin test conversion

Variable

No. (%) employees with 

TST conversion

n = 7 or 8*

No. (%) employees 

without TST conversion

n = 17

P value

American Indian race 6 (75) 5 (29) 0.08

Certified nursing assistant 5 (75) 3 (18) 0.01

Work primarily in ACU 6 (75) 13 (76) 1

Have underlying high-risk 

 condition 1 (12) 0 (0) 0.3

Knew at least two active 

TB symptoms 5 (71) 14 (82) 0.6

Reported access to

 respiratory protection 7 (100) 17 (100) 1

Underwent respirator 

training 5 (71) 15 (88) 0.6

Underwent respirator fit 

 testing 4 (57) 11 (61) 0.7

Ever wore a non-fit tested 

 respirator 4 (57) 5 (31) 0.4

*Sample size varied because one employee was not interviewed but information was gathered from hospital records.
Health Hazard Evaluation Report 2011-0137-3159 Page 17

Results

 (continued) Observation of a Respirator Fit-testing 

Session

At the time of our visit, the medical center’s fit-testing session 

included N95 respirator training with no stand-alone training 

session for these types of respirators. During the two fit tests, we 

observed deficiencies in the respirator training components as 

required by the OSHA respiratory protection standard [29 CFR 

1910.134]. For example, the training we observed did not include 

information on the limitations and capabilities of the respirator or 

procedures for maintenance and storage of the respirator.

The medical center employed qualitative fit testing, consisting 

of a sensitivity test and a fit test using saccharin. Both employees 

whose fit tests we observed passed their tests. Although the 

medical center’s written fit-testing procedures included all the 

elements required by the OSHA respiratory protection standard 

[29 CFR 1910.134], we noted the following deviations from these 

procedures.

● During the first fit test, the employee had the top strap of 

the Kimberly Clark PFR95 respirator placed correctly over 

the ear and high at the top back of his head, but the bottom 

strap was incorrectly placed above his ears rather than below 

the ears. During the second fit test, the employee had the 

upper strap of the 3M 1860 respirator crossed over the lower 

strap, and both were positioned low on her head. Neither of 

these inappropriate placements was corrected by the fit tester. 

Typically, for N95 respirators, when head straps are placed 

properly, the lower strap should be worn around the neck, 

below the ears. The top strap should sit above the ears and 

around the crown of the head, securing the filtering facepiece 

respirator to the user’s face [NIOSH 2011]. Failure to wear 

a respirator as designed compromises the fit and leads to 

insufficient protection.

● Only one of the two employees was given a mirror to assist 

with positioning the respirator on the face. Part 1, Section 

A.1 of Appendix A of the OSHA respiratory protection 

standard, states that “A mirror shall be available to assist the 

subject in evaluating the fit and positioning of the respirator” 

[29 CFR 1910.134].
Page 18 Health Hazard Evaluation Report 2011-0137-3159

Results

 (continued) ● Neither employee wore their respirator for the recommended 

5 minutes to test for comfort [29 CFR 1910.134].

● The medical center’s tuberculosis control program policy 

states that each exercise shall be performed for 1 minute, 

and the aerosol concentration should be replenished using 

half of the original number of squeezes every 30 seconds. 

This protocol was not followed. The test exercises were not 

timed, many lasted less than 1 minute, and the aerosol 

concentration was not replenished every 30 seconds.

Discussion

Healthcare personnel in the United States have been shown to 

be at higher risk of acquiring TB than the general population 

[Menzies et al. 2007]. In the United States, multiple healthcareassociated TB outbreaks have been reported with both patient-topatient and patient-to-healthcare personnel transmission occurring 

[Cookson and Jarvis 1997]. Consistently, the most important factor 

favoring nosocomial transmission has been close contact with 

patients with unrecognized active TB disease [Craven et al. 1975; 

Catanzaro 1982; Kantor et al. 1988; Pearson et al. 1992; Griffith et 

al. 1995].

In our evaluation, a noticeable increase in the number of 

employees with a TST conversion occurred in 2011. Of the 18 

conversions, 10 occurred in employees documented in hospital 

records as having worked in the hospital during a single active 

TB patient’s stay when that patient was not in AII. This finding 

suggests that hospital transmission occurred in these cases. Prompt 

symptom recognition, consideration of active TB as a diagnosis, 

and subsequent AII and respiratory protection usage were all 

delayed and contributed to this outbreak.

Our analysis revealed that certified nursing assistants were 

significantly more likely to have a TST conversion than other 

hospital employees. Multiple studies have shown that physicians, 

nurses, and respiratory therapists are at high risk [Catanzaro 1982; 

Dooley et al. 1992; Zaza et al. 1995; Boudreau et al. 1997]. Most 

studies have grouped nursing assistants, also known as nursing 

technicians or nurse aides, together with registered nurses. One 

study, separating nursing assistants from registered nurses, showed 

that nursing assistants had higher rates of TST conversion [Ball 

1997]. Nursing assistants, medical support assistants, and clerks are 

among the first healthcare personnel to encounter a patient in the 
Health Hazard Evaluation Report 2011-0137-3159 Page 19

Discussion

 (continued) ED or on admission to an inpatient unit before a determination 

of isolation precautions has been made. Nursing assistants often 

evaluate a patient’s vital signs before a comprehensive medical 

assessment has been conducted. It is important to convey a 

patient’s need for isolation precautions immediately after the 

assessment has been made and immediately upon admission to an 

inpatient unit.

In addition to their daily responsibilities, the nursing assistants at 

this hospital also served as interpreters for some of the patients; 

this task requires close face-to-face contact with patients. Some 

nursing assistants recalled interpreting for the reportedly hard 

of hearing Patient 1 when she was not in AII, which may have 

facilitated TB transmission.

Although the medical center’s tuberculosis control program 

policy is comprehensive, our investigation revealed gaps in the 

implementation of the administrative, engineering, and PPE 

controls. It is likely that some of these deficiencies contributed to 

the outbreak at the hospital.

First, the TB technician position was not continuously filled for 

close to 2 years before our investigation. During this time, the ICP 

was responsible for all infection control and occupational health 

activities at the medical center. These activities include employee 

TST screening and administration of the employee respiratory 

protection program. Having a permanent TB technician, an ICP, 

and an employee health nurse will facilitate managing the medical 

center’s TB control program and aid in addressing some of the 

deficiencies we noted.

Second, only 21% of the 39 interviewed employees reported ever 

having attended any TB training or educational sessions during 

their employment at the hospital. Our interviews revealed gaps in 

their knowledge about the symptoms of active TB, the difference 

between latent and active TB, as well as the procedures for a 

patient suspected of having active TB and an employee exposed 

to a patient with active TB. General TB training of all hospital 

employees is necessary upon hire and annually [CDC 2005].

Third, on the basis of less than full compliance with the TST 

screening program, efforts to improve and enforce screening should 

be strengthened. These efforts should include having all eligible 

employees participate in the testing and return for reading.
Page 20 Health Hazard Evaluation Report 2011-0137-3159

Discussion

 (continued) Fourth, although the hospital’s HVAC system in the AII rooms 

was a constant air volume system that exhausted air directly outside 

of the building without recirculation, we observed ventilation 

deficiencies. These deficiencies could increase the potential for 

Mycobacterium tuberculosis transmission from patients with active TB 

disease housed in AII rooms to hospital staff and other patients. 

The electronic pressure monitors were last calibrated 12 years ago 

on installation. The relative pressure difference reading on these 

units were often very different than the readings taken with our 

calibrated micromanometer. In some cases the electronic pressure 

monitors indicated that AII rooms were under negative pressure, 

but our measurements (including visual smoke testing and 

micromanometer readings) indicated that AII rooms were under 

positive pressure. This problem has been reported commonly in 

the scientific literature. In one study of 38 hospital AII rooms 

with electrical or mechanical devices to continuously monitor air 

pressurization, half had actual airflow at the door in the direction 

opposite that indicated by the continuous monitors [Pavelchak 

et al. 2000]. For this reason, CDC recommends daily monitoring 

of rooms with pressure sensors with smoke tubes or other visual 

methods when the rooms are used by patients with known or 

suspected TB.

The electronic door monitors allowed staff to easily switch AII 

rooms from positive to negative pressure. Though all of the AII 

rooms were supposed to be in negative pressure mode, we found 

that the controls for some rooms were in the positive pressure 

mode and had to be switched to the negative pressure mode before 

we made our measurements. Additionally, the electronic door 

monitors allowed users to reverse the dampers in the exhaust 

ductwork, which added additional confusion to the function of the 

ventilation system in the AII rooms.

In several AII rooms, airflow parameters including direction 

of airflow, relative pressure difference between AII rooms 

and adjacent areas, and calculated ACH did not meet CDC 

recommendations [CDC 2005]. Smoke that visualized airflow 

showed that some of the AII rooms were under positive or 

neutral pressure relative to adjacent anterooms and/or hallways. 

Additionally, some of the AII rooms had a pressure differential of 

less than 0.01 inches of water gauge. CDC recommends that AII 

rooms be under negative pressure relative to adjacent areas and 

be maintained at a negative pressure greater than 0.01 inches of 

water gauge [CDC 2005]. CDC also recommends that AII rooms 
Health Hazard Evaluation Report 2011-0137-3159 Page 21

Discussion

 (continued) in hospitals constructed or renovated before 2001 have at least 6 

ACH. Whenever feasible, the airflow should be increased to 12 

ACH [CDC 2005].

Use of the anterooms was suboptimal because the doorways 

between the anterooms and hallways always remained open. When 

used properly, an anteroom can reduce the escape of potentially 

infectious aerosols during the opening and closing of the door 

to an AII room and can buffer an AII room from pressure 

fluctuations in the corridor [CDC 2005]. However, as configured, 

they functioned as less contaminated vestibules between the AII 

rooms and the hallways; this setup might not prevent the escape 

of potentially infectious aerosols into the hallways. We did not 

collect measurements of the direction of airflow between the 

anterooms and hallways because it was hospital practice to keep the 

doorway between these areas open. However, most anterooms (ten 

of thirteen) exhausted more air from these areas than supplied. 

CDC recommends that for anterooms to function properly, more 

air should be exhausted from the room than is supplied to it to 

remove potentially infectious aerosols that can enter from the AII 

room [CDC 2005]. We also noted that many of the anterooms 

provided fewer than 10 ACH, based on exhaust airflow. CDC 

recommends that anterooms provide at least 10 ACH [CDC 2005].

Finally, the hospital uses PAPRs and N95 respirators for protection 

against TB. While employees were trained to use PAPRs, they were 

not trained to use N95 respirators separate from the fit-testing 

session. This training did not include all of the required elements 

of the OSHA respiratory protection standard [29 CFR 1910.134]. 

Comprehensive training will help ensure the proper use of 

respirators by employees, and has been shown to improve the rates 

of adequate fit by fit testing [Winter et al. 2010]. Also of concern 

were the reports by almost one third of interviewed employees that 

they had worn another respirator for which they had not been 

fitted during their employment. We also observed deficiencies in 

the fit-testing procedures, particularly concerning placement of the 

respirators and adherence to the test exercise protocols including 

the replenishment of aerosol concentration, all of which can 

invalidate the test.

Our evaluation was subject to limitations. First, our assessment 

of the ventilation system occurred in August 2011, several months 

after the three active TB patients were hospitalized. Thus, we were 

unable to make any conclusions on the adequacy of engineering 
Page 22 Health Hazard Evaluation Report 2011-0137-3159

Discussion

 (continued) controls during that time. Second, we interviewed only a small 

subset of the more than 1,000 employees at the medical center. 

Thus, the self-reported TB-related practices of employees in other 

locations of the medical center, particularly the outpatient center, 

were not known. Though we interviewed all employees reported 

to have a TST conversion since November 2009, our comparative 

sample of employees without a TST conversion was limited to 

those working in the ED and ACU when Patient 1 was not in 

AII. Because of the small size of this population, we were unable 

to control for multiple factors simultaneously. Third, we observed 

only one fit tester over two fit-testing sessions, so our observations 

were not likely to be representative of all fit-testing sessions and all 

fit testers at the medical center.

Conclusions

A health hazard from exposure to Mycobacterium tuberculosis existed 

at this medical center. Our investigation revealed 18 (2.3%) 

employees with a TST conversion in 2011, and this included one 

employee diagnosed with active TB. Most of these employees 

worked in the hospital during the time when Patient 1 was not in 

AII, suggesting that hospital transmission occurred in these cases. 

Working as a certified nursing assistant was significantly associated 

with having a TST conversion. Although the medical center’s 

written tuberculosis control program policy was comprehensive, 

our investigation revealed gaps in the implementation of 

administrative, engineering, and PPE controls.

Recommendations

On the basis of our findings, we recommend the actions 

listed below to create a more healthful workplace. These 

recommendations include preliminary recommendations given 

at the closing conference of our site visit as well as additional 

recommendations based on further analysis of our findings. 

We encourage the medical center to use a labor-management 

health and safety committee or working group to discuss the 

recommendations in this report and develop an action plan. Those 

involved in the work can best set priorities and assess the feasibility 

of our recommendations for the specific situation at the medical 

center. Our recommendations are based on the hierarchy of 

controls approach according to CDC guidelines [CDC 2005]. This 

approach groups actions by their likely effectiveness in reducing or 

removing hazards.
Health Hazard Evaluation Report 2011-0137-3159 Page 23

Recommendations

 (continued) More comprehensive recommendations can be found in CDC’s 

“Guidelines for Preventing the Transmission of Mycobacterium 

tuberculosis in Health-Care Settings, 2005” at http://www.cdc.

gov/mmwr/preview/mmwrhtml/rr5417a1.htm?s_cid=rr5417a1_e

[CDC 2005].

Administrative Controls

The most important level of TB controls is the use of 

administrative measures to reduce the risk for exposure to persons 

who might have TB disease [CDC 2005]. Administrative controls 

are management-dictated work practices and policies to reduce 

or prevent exposures to workplace hazards. The effectiveness of 

administrative changes in work practices for controlling workplace 

hazards is dependent on management commitment and employee 

acceptance. Regular monitoring and reinforcement are necessary to 

ensure that control policies and procedures are not circumvented 

in the name of convenience.

1. Continue to conduct an annual TB risk assessment using the 

TB risk assessment worksheet found in CDC’s “Guidelines 

for Preventing the Transmission of Mycobacterium tuberculosis

in Health-Care Settings, 2005” [CDC 2005]. This assessment 

serves as an ongoing tool for evaluating the quality of TB 

infection control and identifying needed improvements in 

infection control measures.

2. Provide general TB training during working hours to all 

employees on hire and annually thereafter to ensure a 

thorough understanding of the disease, its transmission, 

and ways to prevent it. Training for employees with direct 

patient contact should include the procedures for patients 

known or suspected of having active TB and for reporting 

healthcare personnel exposure to a patient with active TB. 

Training should be tailored to education level and clinical 

role. General training and education materials can be found 

on CDC’s TB website at http://www.cdc.gov/tb/.

3. Hire a permanent TB technician, and consider separating 

out the duties of the ICP and the employee health nurse.

4. Encourage all triage nurses to offer face masks to any 

patient who is actively coughing or complains of coughing. 
Page 24 Health Hazard Evaluation Report 2011-0137-3159

Recommendations 

(continued) Promptly place any patients with TB symptoms in a 

properly functioning AII room until the patients have had 

three negative smears for AFB in their sputa. Place signs 

indicating AII as soon as the determination is made and 

immediately upon admission to an inpatient unit.

5. Continue annual TST placement and symptom screening of 

all employees with face-to-face patient contact during work 

hours. Define more clearly which employees are considered 

to have direct patient contact and are required to have annual 

TST screening. Medical support assistants in patient areas 

should be considered to have direct patient contact. Enforce 

the requirement for employee TB screening. Enforcement 

methods could include disabling privileges to electronic 

health records or disabling access to patient care areas.

6. Ensure that employees found to have new TST conversions 

have access to a prompt medical evaluation. Try to 

accommodate the schedules of employees who work at night.

7. Close the door between the anteroom and adjacent hallway 

when housing patients with active TB (or other airborne 

infectious diseases) to reduce the escape of potentially infectious 

aerosols when the door to an AII room is opened or closed.

Engineering Controls

Engineering controls are the second line of defense in the TB 

infection control program [CDC 2005]. Engineering controls 

prevent the spread and reduce the concentration of airborne 

Mycobacterium tuberculosis in ambient air. These technologies 

include local exhaust, ventilation, general ventilation, HEPA 

filtration, and ultraviolet germicidal irradiation. Engineering 

controls are very effective in protecting employees without placing 

primary responsibility of implementation on the employee.

1. Do not use rooms Q8, Q11, Q12, Q17, R11, or R21 as AII 

rooms because they are under positive pressure. Also, do 

not use room R9 as an AII room because it is exhausting 

fewer than 6 ACH. Ensure that hospital staff understand 

that these rooms should not be used to house patients 

with known or suspected airborne infectious diseases until 

changes are made to the rooms to meet AII requirements.
Health Hazard Evaluation Report 2011-0137-3159 Page 25

Recommendations 

(continued) 2. Rebalance the HVAC system to ensure that all AII rooms are 

under negative pressure relative to adjacent anterooms and/

or hallways. Additionally, provide at least 6 ACH in all AII 

rooms and at least 10 ACH in anterooms, on the basis of 

exhaust airflow per CDC guidelines [CDC 2005].

3. Reduce the amount of airflow exhausted from the ICU 

anteroom to ensure that this room is maintained under 

positive pressure relative to the adjacent AII room and is 

at neutral or negative pressure relative to the adjacent ICU 

suite. Until this can be done, do not turn on the exhaust 

fan in the ICU AII anteroom when housing patients with 

airborne infectious diseases if employees are using the 

anteroom as an area to don respirators before entering the 

AII room.

4. Disable the mechanically controlled dampers in the 

ducted returns in rooms designated as AII rooms so that 

these rooms cannot be switched into “positive pressure” 

mode. Also, ensure dampers in the exhaust ductwork are 

positioned to maximize exhaust airflow in AII rooms.

5. Follow the CDC-recommended schedule for maintaining 

proper negative pressure in AII rooms [CDC 2005]:

● Check AII rooms for negative pressure before occupancy.

● If an AII room is occupied by a patient, use smoke tubes 

or other visual means to check daily for negative pressure.

● If pressure-sensing devices are used in AII rooms 

occupied by patients with suspected or confirmed 

TB disease, use smoke tubes or other visual means to 

check negative pressure daily.

● If the AII rooms are not being used for patients 

who have suspected or confirmed TB disease but 

potentially could be used for such patients, check 

negative pressure monthly.

6. Instruct staff not to rely on electronic door pressure 

monitors to determine if rooms are under negative 

pressure. These monitors were not calibrated regularly 

and were inaccurate. If the use of the electronic door 

pressure monitors continues, ensure that they are calibrated 

periodically according to manufacturer guidelines.
Page 26 Health Hazard Evaluation Report 2011-0137-3159

Recommendations 

(continued) 7. Confirm that the exhaust filter in the sputum booth is a 

HEPA filter.

Personal Protective Equipment

The third level of the hierarchy of controls is the use of respiratory 

protection in situations that pose a high risk for exposure such 

as AII rooms. PPE is the least effective means for controlling 

employee exposures. Proper use of PPE requires a comprehensive 

program, and calls for a high level of employee involvement and 

commitment to be effective. The use of PPE requires the choice 

of the appropriate equipment to reduce the hazard and the 

development of supporting programs such as training, change-out 

schedules, and medical assessment. PPE should not be relied upon 

as the sole method for limiting employee exposures.

1. Develop, implement, and maintain a written respiratory 

protection program for employees to protect against TB and 

other airborne infectious diseases. All employees who may 

need to wear respirators should receive training, receive 

medical clearance, and undergo fit testing annually as 

defined in the OSHA respiratory protection standard [29

CFR 1910.134].

2. Improve training to include specific indications for 

respirator use and how to put on, wear, and remove 

respiratory protection. Consider offering a training session 

separate from the fit-testing procedures. Having a separate 

training session that multiple employees can attend may also 

be time-saving to fit testers. This training should include 

all required elements defined in the OSHA respiratory 

protection standard [29 CFR 1910.134].

3. Follow the OSHA respiratory protection standard [29 CFR 

1910.134] to ensure that employees use only PAPRs or N95 

respirators for which they have been fit tested.
Health Hazard Evaluation Report 2011-0137-3159 Page 27

Recommendations 

(continued) 4. Ensure that those conducting fit testing follow the 

procedures defined in Appendix A of the OSHA 

respiratory protection standard [29 CFR 1910.134] to 

ensure the validity of the test. Important components of 

fit-testing procedures include:

● Showing the test subject how to put on a respirator, 

how it should be positioned on the face, and how 

to determine an acceptable fit. Straps should not be 

crossed, and a mirror should be available to assist this 

process.

● Having the test subject perform a seal check.

● Describing the fit test, the exercises, and the test 

subject’s responsibilities during the test procedures. 

The respirator to be tested should be worn for at least 

5 minutes before the start of the fit test.

● Having the test subject perform a taste threshold 

screening without wearing a respirator to determine 

whether the individual being tested can detect the 

taste of saccharin.

● Performing each test exercise listed in the medical 

center’s tuberculosis control program policy for 1 

minute. Every 30 seconds, the aerosol concentration 

should be replenished using half of the original 

number of squeezes during the screening test.

5. Repeat fit tests for those employees whose previous fit 

tests did not include all of the required components of fit 

testing as defined in Appendix A of the OSHA respiratory 

protection standard [29 CFR 1910.134].

6. Offer additional training to fit testers to strengthen their 

knowledge about respirators and their use and to improve 

the validity of fit-testing procedures.

7. Conduct annual evaluations of the workplace to ensure 

that the written respiratory protection program is properly 

implemented, and observe employees to ensure that they are 

using the respirators properly [29 CFR 1910.134].
Page 28 Health Hazard Evaluation Report 2011-0137-3159

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[1995]. Tuberculosis outbreak among healthcare workers in a 

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[http://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/

RespSource3.html#donning]. Date accessed: February 2012.
Health Hazard Evaluation Report 2011-0137-3159 Page 29

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Page 30 Health Hazard Evaluation Report 2011-0137-3159

Appendix: Ventilation Measurements

Table A1. Ventilation airflow and pressure measurements and calculated ACH in AII rooms and adjacent 

anterooms on August 9–11, 2011

Room

Measured 

supply airflow 

(CFM)

Measured 

exhaust airflow 

(CFM)

Calculated 

ACH*

Observed 

air pressure 

relationship to 

adjacent area

Pressure 

differential 

relative to 

adjacent area 

(inches of 

water gauge)

Observed 

electronic 

door pressure 

monitor reading 

(inches of 

water gauge)

ED and ICU

ED6 161 310 15.6 Negative to ED −0.0105 No monitor

ICU (anteroom 

fan on) 284 487 21.4

Negative to 

ICU suite; 

slightly positive 

to anteroom

−0.0140

 (ICU suite)

+0.0005 

(anteroom)

−0.0085

ICU (anteroom 

fan off) 284 487 21.4

Negative to 

ICU suite and 

anteroom

−0.0250

 (ICU suite)

−0.0250 

(anteroom)

+0.115

Anteroom ICU 45 203 33.6 Negative to 

ICU suite Not measured NA

ACU

Patient room 

R9 154 94 5.7

Negative to 

anteroom and 

hallway

−0.0075 

(anteroom) 

−0.0080 

(hallway)

−0.00093

Patient room 

R11 145 36 2.2

Positive to 

anteroom and 

hallway

+0.0060 

(anteroom)

+0.0060 

(hallway)

−0.00160

Anteroom R9/

R11 0 51 7.2 Not measured Not measured NA

Patient room 

R12 207 242 14.5

Negative to 

anteroom and 

hallway

−0.0125 

(anteroom)

−0.0105 

(hallway)

Not operable

Patient room 

R14 185 223 13.4

Negative to 

anteroom and 

hallway

−0.0150 

(anteroom)

Not measured 

relative to 

hallway

−0.00635

Anteroom R12/

R14 0 139 17.7 Not measured Not measured NA

Patient room 

R21 193 56 3.4

Positive to 

anteroom and 

hallway

+0.0085 

(anteroom)

+0.0075 

(hallway)

−0.0050

Patient room 

R23 177 197 12.0

Negative to 

anteroom and 

hallway

−0.0040 

(anteroom)

−0.0040 

(hallway)

−0.0020
Health Hazard Evaluation Report 2011-0137-3159 Page 31

Appendix: Ventilation Measurements

 (continued)

Table A1. Ventilation airflow and pressure measurements and calculated ACH in AII rooms and adjacent 

anterooms on August 9–11, 2011 (continued)

Room

Measured 

supply airflow 

(CFM)

Measured 

exhaust airflow 

(CFM)

Calculated 

ACH*

Observed 

air pressure 

relationship to 

adjacent area

Pressure 

differential 

relative to 

adjacent area 

(inches of 

water gauge)

Observed 

electronic 

door pressure 

monitor reading 

(inches of 

water gauge)

Anteroom R21/

R23 48 54 6.9 Not measured Not measured NA

Patient room 

R24 187 153 9.3

Negative to 

anteroom and 

hallway

−0.0140 

(anteroom)

−0.0070 

(hallway)

Not collected

Patient room 

R26 219 384 22.9

Negative to 

anteroom and 

hallway

−0.0265 

(anteroom)

−0.0225 

(hallway)

−0.0215

Anteroom R24/

R26 0 46 6.0 Not measured Not measured NA

Pediatric Unit

Patient room 

Q8 264 223 11.2 Neutral to anteroom −0.0020 −0.00049

Anteroom Q8 37 37 6.7 Not measured Not measured NA

Patient room 

Q9 178 185 10.0 Negative to anteroom −0.0060 −0.0066

Anteroom Q9 0 0 0 Not measured Not measured NA

Patient room 

Q10 164 224 12.1 Negative to anteroom −0.01450 −0.0145

Anteroom Q10 0 72 13.2 Not measured Not measured NA

Patient room 

Q11 148 164 9.9 Positive to anteroom +0.0070 −0.00013

Anteroom Q11 No supply vent 68 11.1 Not measured Not measured NA

Patient room 

Q12 297 86 5.2 Positive to anteroom +0.012 Not operable

Anteroom Q12 No supply vent 50 8.2 Not measured Not measured NA

Patient room 

Q17 333 251 13.7 Positive to anteroom +0.0060 −0.00020

Anteroom Q17 51 69 12.6 Not measured Not measured NA

Patient room 

Q18 195 280 15.1 Negative to anteroom −0.0050 −0.00350

Anteroom Q18 62 88 16.2 Not measured Not measured NA

Patient room 

Q19 172 133 7.2 Negative to anteroom −0.0060 −0.0097

Anteroom Q19 48 0 0 Not measured Not measured NA

* Based on exhaust airflow measurements in patient room
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Health Hazard Evaluation Report 2011-0137-3159 Page 35

The Hazard Evaluations and Technical Assistance Branch 

(HETAB) of the National Institute for Occupational Safety and 

Health (NIOSH) conducts field investigations of possible health 

hazards in the workplace. These investigations are conducted 

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

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

the Secretary of Health and Human Services, following a written 

request from any employer or authorized representative of 

employees, to determine whether any substance normally found 

in the place of employment has potentially toxic effects in such 

concentrations as used or found. HETAB also provides, upon 

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

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

control occupational health hazards and to prevent related trauma 

and disease.

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.

This report was prepared by Marie A. de Perio and R. Todd 

Niemeier of HETAB, Division of Surveillance, Hazard Evaluations 

and Field Studies. Industrial hygiene equipment and logistical 

support were provided by Donald Booher and Karl Feldmann. 

Medical field assistance and statistical support were provided by 

Anne Marie France of the Division of Tuberculosis Elimination 

at the Centers for Disease Control and Prevention. Health 

communication assistance was provided by Stefanie Evans. 

Editorial assistance was provided by Ellen Galloway. Desktop 

publishing was performed by Greg Hartle.

Copies of this report have been sent to employee and management 

representatives at the medical center, the state health department, 

the tribal health department, and the Occupational Safety and 

Health Administration Regional Office. This report is not 

copyrighted and may be freely reproduced. The report may be 

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may be purchased from the National Technical Information Service 

at 5825 Port Royal Road, Springfield, Virginia 22161.

Acknowledgments and

Availability of Report
Below is a recommended citation for this report:

NIOSH [2012]. Health hazard evaluation report: evaluation of exposure to 

tuberculosis among employees at a medical center — Arizona. By de Perio MA, 

Niemeier RT. Cincinnati, OH: U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, National Institute for Occupational 

Safety and Health, NIOSH HETA No. 2011-0137-3159.

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