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HHE Search Results
62 HHE reports were found based on your search terms. Reports are listed in order of year published with the most recently published reports listed first.
Year Published and Title
(2013) Health hazard evaluation report: evaluation of ventilation controls for tuberculosis prevention at a hospital. (Click to open report) The HHE Program evaluated ventilation controls at a hospital after latent tuberculosis infections were identified among hospital staff. Investigators measured ventilation airflow in some airborne infection isolation rooms, airborne infection isolation anterooms, and standard patient rooms; they found that air in the isolation rooms and anterooms was exhausted directly to the outside as recommended. All but one of the isolation rooms measured met the Centers for Disease Control and Prevention (CD... (Click to show more)The HHE Program evaluated ventilation controls at a hospital after latent tuberculosis infections were identified among hospital staff. Investigators measured ventilation airflow in some airborne infection isolation rooms, airborne infection isolation anterooms, and standard patient rooms; they found that air in the isolation rooms and anterooms was exhausted directly to the outside as recommended. All but one of the isolation rooms measured met the Centers for Disease Control and Prevention (CDC) guideline of providing at least six air changes per hour. Investigators recommended that the anterooms adjacent to the isolation rooms be rebalanced. All but one of the isolation rooms measured met the CDC guidelines for negative pressure (greater than or equal to 0.01 inches of water gauge). HHE Program investigators recommended that the employer follow CDC recommendations for airflow rates in isolation rooms and anterooms. A sufficient number of isolation rooms should be maintained to house patients with known or suspected active tuberculosis disease. Investigators also evaluated the use of portable air cleaners that could be used in standard patient rooms because of an insufficient number of airborne isolation rooms. As a result, investigators recommended that when portable air cleaners with high efficiency particulate air filtration and ultraviolet germicidal irradiation are used, their placement be carefully considered to achieve good air mixing. Additionally, they should be exhausted directly outside, the rooms should be maintained under negative pressure, and there should be no recirculation of room air to other parts of the facility. Investigators recommended that employees report suspected problems with the ventilation system in isolation rooms and anterooms to supervisors immediately.
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(2012) Exposure to tuberculosis among employees at a medical center - Arizona. (Click to open report) 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 (TB). 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 asse... (Click to show more)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 (TB). 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 airborne infection isolation (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 tuberculin skin test (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 personal protective equipment (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 air changes per hour (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 heating, ventilating, and air-conditioning (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 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.
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(2011) Respiratory protection practices for employees at federal immigration and customs agency workplaces - Nationwide. (Click to open report) In July 2009, NIOSH received an HHE request from the American Federation of Government Employees. The union was concerned about respiratory protection for federal immigration and customs agency employees during the pH1N1 pandemic. NIOSH investigators reviewed the agency's written respiratory protection procedures, observed a respirator fit-testing session for employees at agency headquarters, and surveyed employees nationwide about respiratory protection practices. We found that the agency's res... (Click to show more)In July 2009, NIOSH received an HHE request from the American Federation of Government Employees. The union was concerned about respiratory protection for federal immigration and customs agency employees during the pH1N1 pandemic. NIOSH investigators reviewed the agency's written respiratory protection procedures, observed a respirator fit-testing session for employees at agency headquarters, and surveyed employees nationwide about respiratory protection practices. We found that the agency's respiratory protection policy, the respirator medical evaluation questionnaire, the qualitative fit-testing protocol, and the slide presentation serving as training for fit testers were comprehensive. The quality of the observed respirator fit-testing procedures was good. However, we identified several areas that needed improvement. Though the response rate for our survey was suboptimal with 2,218 responding employees, we found that that most respondents, particularly those from DRO and OI, have face-to-face contact with immigrants in their current job. This contact places them at risk for exposure to airborne infectious agents, including Mycobacterium tuberculosis, influenza virus, rubeola virus, and varicella zoster virus. Most respondents completed all of the steps required for respirator use (medical clearance, respirator training, respirator fit testing). However, some gaps between medical clearance and respirator training existed. We also found low employee compliance with respirator usage and annual tuberculosis screening. The written respiratory protection programs were not readily available in some workplaces. The agency should maintain a written respiratory protection program for all workplaces to protect against airborne infectious agents and other respiratory hazards. The agency should require and arrange fit testing for employees at least annually and verify medical clearance prior to the fit test. Clear written procedures for the use of respirators should be developed and maintained, and specific indications for respirator usage should be included in training. Annual evaluations of the workplaces to ensure that the written respiratory protection program is being properly implemented should be conducted. Training provided to employees and fit testers should be improved to include more information on the technical capabilities of respirators and more specific instructions for performing face seal checks and for donning and doffing respirators. Employees who should undergo routine tuberculosis screening should be identified and informed. Finally, annual influenza vaccination should be recommended to all employees.
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(2010) Exposure to tuberculosis among immigration employees, U.S. Immigration and Customs Enforcement Detention and Removal Operations, Chicago, Illinois and Broadview, Illinois. (Click to open report) In January 2009, NIOSH received an HHE request from the American Federation of Government Employees, Local 2718. The request concerned the potential for transmission of TB at the U.S. ICE BSSA facility in Broadview, Illinois. While no known cases of active TB had occurred among employees, the incidence of latent TB infection among employees was unknown. NIOSH investigators made an initial site visit to BSSA on April 8-9, 2009. We walked through the facility and observed work processes, practices... (Click to show more)In January 2009, NIOSH received an HHE request from the American Federation of Government Employees, Local 2718. The request concerned the potential for transmission of TB at the U.S. ICE BSSA facility in Broadview, Illinois. While no known cases of active TB had occurred among employees, the incidence of latent TB infection among employees was unknown. NIOSH investigators made an initial site visit to BSSA on April 8-9, 2009. We walked through the facility and observed work processes, practices, and conditions. We spoke with employees about health and workplace concerns about TB and collected environmental and ventilation measurements. We also held confidential interviews with all 29 employees present at the facility. Most employees reported having daily direct contact with detainees, and none of the employees reported receiving general TB training, respirator fit testing, or respirator training during their employment at BSSA. Many employees were unaware of the ICE recommendation that they undergo periodic TB screening. We also learned that the return air from the detainee areas, including the isolation room, was recirculated throughout BSSA. In addition, all of the detainee areas, including the isolation room, were positively pressurized relative to the adjacent hallway and employee areas. Both situations result in air that was shared between employees and detainees, which could lead to an increased risk of exposure if airborne infectious agents (including Mycobacterium tuberculosis) are present. On July 10, 2009, NIOSH received a second HHE request from the American Federation of Government Employees, Local 2718 concerning the potential for transmission of TB at the ICE CDO in Chicago, Illinois. We made a second site visit to BSSA and an initial site visit to the CDO on August 10-12, 2009. During that visit, we walked through both facilities and observed work processes, practices, and conditions. We spoke with employees about TB-related health and workplace concerns and collected environmental and ventilation measurements. We also screened employees at both facilities for TB with both the TST skin test and QFT GIT blood test methods. At the CDO, the HVAC system in the detainee area is a constant air volume system that exhausts air directly out of the building without recirculation, which is an optimal design. However, the calculated ACH in the holding cells, processing area, and courtrooms were below those recommended by CDC. We also noted that the air flow movement between many of the holding cells and the processing area and between Courtroom B and a secure hallway was bidirectional. These deficiencies can increase the risk of exposure if airborne infectious agents (including Mycobacterium tuberculosis) are present. Most ICE employees participate in job activities that place them at risk of acquiring TB infection, including transporting and interviewing detainees and supervising court visits. Despite this, few participants reported having annual TB screening. Even when we offered TB screening on-site, the number of employees who returned for the TST reading and second step placement was low. All employees who underwent blood collection for the QFT-GIT completed screening. Our evaluation demonstrates the feasibility and practicality of the QFT-GIT as the preferred TB screening method among ICE employees who often have unpredictable schedules. We recommend that the Field Office Director and other local ICE supervisors familiarize themselves with ICE's existing tuberculosis exposure control plan and then develop plans specific for both BSSA and the CDO. A separate constant air volume HVAC system should be designed for BSSA to provide single-pass exhaust ventilation in the detainee holding cells, isolation room, and processing area. Negative pressure should be maintained in these areas relative to all adjacent administrative areas at BSSA. The HVAC system in the detainee areas at the CDO should be rebalanced to provide the appropriate ACH and air flow patterns to minimize the potential for transmission of TB. General training on TB should be provided annually to all employees. All employees should be made aware that annual TB screening is recommended and that it is offered at no cost through FOH. FOH should consider conducting on-site TB screening on predetermined dates and hours at BSSA and CDO and using IGRA testing instead of TST testing to improve participation rates. A respiratory protection program should be implemented for all employees to minimize the potential for transmission of TB. All employees should receive training and medical clearance, and undergo fit testing as defined in the OSHA Respiratory Protection Standard (29 CFR 1910.134).
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(2007) Denver Sheriff's Department, Denver, Colorado. (Click to open report) In September 2006, employees at the Denver Sheriff's Department, Denver, Colorado, requested that the National Institute for Occupational Safety and Health (NIOSH) evaluate potential employee exposures to infectious agents from inmates housed at the facility. The specific diseases listed in the employee request included tuberculosis (TB), methicillin-resistant staphylococcus aureus (MRSA), and Serratia marcescens (serratia). During the NIOSH visit in September 2006, employee and management repr... (Click to show more)In September 2006, employees at the Denver Sheriff's Department, Denver, Colorado, requested that the National Institute for Occupational Safety and Health (NIOSH) evaluate potential employee exposures to infectious agents from inmates housed at the facility. The specific diseases listed in the employee request included tuberculosis (TB), methicillin-resistant staphylococcus aureus (MRSA), and Serratia marcescens (serratia). During the NIOSH visit in September 2006, employee and management representatives provided information about the Denver Sheriff's Department infection control procedures and ventilation system and participated with NIOSH representatives in a walk-through tour of the facility. Confidential employee requesters and Department medical providers were interviewed by phone at another time. There were no reports of infections with TB, MRSA, or serratia among any of the Denver Sheriff's Department employees. Employee exposures to potentially ill inmates were limited by procedures followed at the Denver Sheriff's Department. These included: medical screening of incoming inmates, transfer of sick inmates to an offsite medical location, preventing inmate presence on the first-floor administrative area by moving inmates directly from the basement entry area to the housing areas on the second-fourth floors, regular cleaning of inmate housing areas, and exhausting of 100% of the air in the inmate housing areas to the outdoors. Although our evaluation did not document occupationally-acquired infections with TB, MRSA, or serratia in employees of the Denver Sheriff's Department, correctional facilities are considered to be workplaces where the risk of certain infectious disease exposures is greater than in the general population. These include TB, the human immunodeficiency virus, and hepatitis B and C. Recommendations to decrease the likelihood of these exposures to employees at the Denver Sheriff's Department are provided in this report. Although no occupationally-acquired TB, MRSA, or serratia infections were identified in Denver Sheriff's Department employees, our evaluation found areas where improvements are warranted. Correctional facilities are considered to be work environments with an elevated risk for occupational exposure to TB, hepatitis B and C, and the human immunodeficiency virus, and consensus infection control standards and guidelines have been established to prevent disease transmission in these facilities. We recommend that additional infection control procedures, including hepatitis B vaccination and TB screening in employees, be implemented per established standards and guidelines and that current inmate transport policies and 100 percent exhaust ventilation in the inmate holding areas be continued to help limit the risk of infectious-disease exposure to employees.
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(2007) Tuberculin skin test conversions at a Mississippi fire department, City of Meridian Fire Department, Meridian, Mississippi. (Click to open report) In October 2006, NIOSH received a management request for an HHE at the City of Meridian Fire Department in Meridian, Mississippi. The Fire Chief submitted the HHE request because 12 firefighters tested positive for latent tuberculosis infection from 2005-2006. On October 24-26, 2006, NIOSH medical investigators conducted a site visit. We held an opening conference with management and union representatives to discuss the HHE request. We conducted employee interviews and collected blood samples fo... (Click to show more)In October 2006, NIOSH received a management request for an HHE at the City of Meridian Fire Department in Meridian, Mississippi. The Fire Chief submitted the HHE request because 12 firefighters tested positive for latent tuberculosis infection from 2005-2006. On October 24-26, 2006, NIOSH medical investigators conducted a site visit. We held an opening conference with management and union representatives to discuss the HHE request. We conducted employee interviews and collected blood samples for TB testing. Individuals were mailed their blood test results on October 31, 2006. A follow-up site visit was conducted on December 11-13, 2006. NIOSH medical investigators, in conjunction with State of Mississippi District 6 Tuberculosis Program staff, conducted follow-up TSTs for participants to determine their eligibility for future TST as part of their medical surveillance program and to help confirm the results of our investigation. Individuals were verbally notified of their test results at the time of TST interpretation, and written results were mailed to participants on December 15, 2006. Interviews with Fire Department management, firefighters, District 6 Tuberculosis Program personnel; and an evaluation of the department's EMS procedures (no patient transport) found the department to be at low risk for TB, using CDC guidelines. All twelve participants' blood samples were tested for evidence of TB infection using QuantiFERON-TB Gold methodology; all twelve samples tested negative, indicating that these firefighters were not infected with Mycobacterium tuberculosis. We found discrepancies in the TB screening program at the hospital that administered the Fire Department's occupational medical screening program, when compared to CDC recommendations. These discrepancies led to the false-positive TST results that were confirmed by the blood test and subsequent follow-up TST performed in December 2006. We recommend two options concerning future tuberculosis screening for Meridian Fire Department firefighters. If management decides to continue annual tuberculosis screening, it should be conducted following CDC guidelines. If management decides to conduct an annual TB risk assessment for department firefighters to determine testing frequency, this assessment should be conducted with the assistance and close cooperation of the State of Mississippi District 6 Tuberculosis Program staff. Management and union officials should emphasize the importance of attending all medical appointments, continue periodic refresher training on tuberculosis and bloodborne pathogens, and incorporate N95 respirator training and fit-testing into their respiratory protection program.
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(2006) New York University School of Medicine, New York City, New York. (Click to open report) On December 19, 2003, the National Institute for Occupational Safety and Health (NIOSH) received a request for a health hazard evaluation (HHE) from the Department of Environmental and Occupational Safety and Health at the New York University School of Medicine in New York City, New York. The request cited concerns regarding potential employee exposure to aerosolized Mycobacterium tuberculosis (M. tuberculosis) in an animal biosafety level 3 (ABSL3) laboratory. Specific activities of concern i... (Click to show more)On December 19, 2003, the National Institute for Occupational Safety and Health (NIOSH) received a request for a health hazard evaluation (HHE) from the Department of Environmental and Occupational Safety and Health at the New York University School of Medicine in New York City, New York. The request cited concerns regarding potential employee exposure to aerosolized Mycobacterium tuberculosis (M. tuberculosis) in an animal biosafety level 3 (ABSL3) laboratory. Specific activities of concern included aerosolizing M. tuberculosis, caretaking of infected mice, using a cryostat to cut infected tissue, and manipulating infected tissue in ways that could generate aerosols. On May 19-21, 2004, investigators from NIOSH conducted a site visit to the facility. Area air samples were collected in the laboratory for airborne M. tuberculosis. Information was gathered and observations were made regarding the personal protective equipment (PPE) used by employees in the laboratory, as well as the current medical surveillance programs in place. Smoke tubes were used to verify the pressure relationships between the rooms of the laboratory. The NIOSH investigators concluded that a health hazard did not exist from exposure to M. tuberculosis. The work practices and procedures provide a high level of protection against potential occupational exposure to M. tuberculosis. No evidence was collected that suggested the M. tuberculosis was being aerosolized outside of contained, controlled chambers. Recommendations are made to continue current safety practices and work procedures and to maintain a schedule of regular maintenance on the laboratory's ventilation system.
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(2006) Swannanoa Valley Youth Development Center, Swannanoa, North Carolina. (Click to open report) The National Institute for Occupational Safety and Health (NIOSH) received a confidential request from employees at the North Carolina Department of Juvenile Justice and Delinquency Prevention's (DJJDP) Swannanoa Valley Youth Development Center (SVYDC) in Swannanoa, North Carolina, to conduct an investigation of tuberculosis (TB) control, indoor air quality (IAQ), and asbestos management at that facility. Employees expressed concerns about possible TB exposure after hearing that at least one of ... (Click to show more)The National Institute for Occupational Safety and Health (NIOSH) received a confidential request from employees at the North Carolina Department of Juvenile Justice and Delinquency Prevention's (DJJDP) Swannanoa Valley Youth Development Center (SVYDC) in Swannanoa, North Carolina, to conduct an investigation of tuberculosis (TB) control, indoor air quality (IAQ), and asbestos management at that facility. Employees expressed concerns about possible TB exposure after hearing that at least one of the facility's students was being treated with TB medication and that one employee recently had a positive tuberculin skin test (TST) result when tested by a private physician. They questioned the change in policy that occurred in 2000, whereby annual skin testing for employees was replaced with testing at hire only. In addition, employees expressed concerns about indoor air quality, including exposure to mold. They reported asthma and other respiratory symptoms. Finally, employees expressed concerns about possible exposure to asbestos. They reported broken floor tiles that they believed contained asbestos as well as construction debris containing asbestos that had been buried on the campus grounds. The NIOSH response consisted of several phone interviews with the requesters and management to gather information, phone interviews with members of the state health department, a two-day site visit by NIOSH staff, review of the state's tuberculosis control policy manual, and review of the facility's operations and management plan. During the site visit, a NIOSH industrial hygienist conducted a walkthrough of the facility's buildings, evaluated building ventilation systems, and interviewed both SVYDC and DJJDP safety officers. A NIOSH medical officer reviewed the facility's TB control program (including skin testing protocols and results for students and employees), inquired about its respiratory protection program, and interviewed the facility and state health department health care personnel responsible for infection control. A TB control nurse consultant from the state health department participated in the site visit, including the review of the facility's TB control program. The TB control program includes one-step TST at baseline (pre-admission) and every two years for students; and one-step TST at hire for employees. Employees do not receive information on TB as part of their safety training and do not participate in a respiratory protection program for TB. Review of student TST results for the past three years revealed five newly positive results in students who had negative baseline results. According to the facility and state health department health care personnel, there have not been any cases of infectious TB among the students for at least the past three years. Mold growth in some of the student shower areas was observed. Some of the ventilation ducts had substantial dust build-up. Concentrations of carbon dioxide were found to be elevated in the clinic area when it was occupied by multiple people. Materials identified in the facility's Asbestos Management Plan as containing asbestos were noted to be intact with the exception of several broken floor tiles in one area. NIOSH staff conducted a two-day site visit to the Swannanoa Valley Youth Development Center in Swannanoa, North Carolina to address employee concerns about exposure to TB, indoor air quality, exposure to asbestos, and health effects that employees were experiencing. Students are skin-tested for TB every two years. While some students have had tuberculin skin test conversions, there have been no documented cases of infectious TB among students. Employees are skin-tested at hire only. One employee who had a positive test in 2005 when tested by a private physician may have had a workplace exposure. Further investigation is recommended and annual employee testing should be initiated. A respiratory protection program for TB was not in place for employees and should be established. A small amount of mold growth was noted in the student showers and there was evidence of roof leaks in the cafeteria. Real-time measurements indicated that carbon dioxide levels in the clinic area were elevated when it was occupied by multiple people, indicating that fresh air supply was inadequate. Floor tiles in the Greenwood Cottage A-wing had been identified in the Asbestos Management Plan as containing asbestos. Several of these tiles were found to be broken and should be replaced.
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(2005) El Dorado County Health Department, Placerville, CA and South Lake Tahoe, CA. (Click to open report) On September 30, 2004, the National Institute for Occupational Safety and Health (NIOSH) received a request for technical assistance from a management official at the El Dorado County Health Department in Placerville, California concerning the potential for airborne transmission of infectious diseases within health department clinics. At the time of the request, no health effects had been reported. NIOSH representatives visited the El Dorado County Health Departments in Placerville, California a... (Click to show more)On September 30, 2004, the National Institute for Occupational Safety and Health (NIOSH) received a request for technical assistance from a management official at the El Dorado County Health Department in Placerville, California concerning the potential for airborne transmission of infectious diseases within health department clinics. At the time of the request, no health effects had been reported. NIOSH representatives visited the El Dorado County Health Departments in Placerville, California and in South Lake Tahoe, California during March 7-10, 2005, to conduct a hazard evaluation. During the evaluation, indoor environmental quality (IEQ) parameters and the heating, ventilation, and air conditioning (HVAC) systems were evaluated. The IEQ measurements did not indicate a problem with temperature, relative humidity, or carbon dioxide levels. However, many supply and return air diffusers were discovered to be either non-functioning, obstructed, or functioning at a capacity other than intended. None of the exam rooms at either clinic met the criteria for airborne infection isolation. Airborne infection isolation rooms should be used when providing care for patients with airborne infections such as tuberculosis and chickenpox. The results of the IEQ measurements confirmed that the indoor environmental quality is within acceptable ranges. However, the air flow measurements indicated problems with the function of diffusers, thus affecting the supply of outdoor air and reducing the potential for dilution of normal room contaminants and potentially infectious aerosols. This report provides recommendations to address these issues and advises the designation of an airborne isolation infection room at both clinics.
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(2005) Salvation Army Harbor Light Center, St. Louis, Missouri. (Click to open report) On August 20, 2003, the National Institute for Occupational Safety and Health (NIOSH) received a request for technical assistance concerning a tuberculosis (TB) outbreak at the Salvation Army Harbor Light Center in St. Louis, Missouri. The request was made by the Division of Tuberculosis Elimination (DTBE), National Center for HIV, STD and TB Prevention (NCHSTP), which was investigating the outbreak at the request of the Missouri Department of Health and Senior Services (MO DHSS). Between Februa... (Click to show more)On August 20, 2003, the National Institute for Occupational Safety and Health (NIOSH) received a request for technical assistance concerning a tuberculosis (TB) outbreak at the Salvation Army Harbor Light Center in St. Louis, Missouri. The request was made by the Division of Tuberculosis Elimination (DTBE), National Center for HIV, STD and TB Prevention (NCHSTP), which was investigating the outbreak at the request of the Missouri Department of Health and Senior Services (MO DHSS). Between February 2001 and August 2003, MO DHSS had identified a total of 19 cases of active TB linked to the Harbor Light shelter. NIOSH investigators made five visits to the Salvation Army Harbor Light Center between September 2003 and October 2004. Thorough inspections of the shelter air-handling units (AHUs) were conducted, and ventilation air flow rates were monitored. Tracer gas studies were conducted to calculate air exchange rates and describe air flow patterns. This work revealed that the majority of the AHUs at the shelter were in poor repair and in need of cleaning and maintenance. Following our recommendations, the shelter improved the overall cleanliness of the AHUs and has instituted regular maintenance procedures. The filters in all AHUs were upgraded to MERV 11 filters from the original MERV 7 filters. Despite some AHU improvements in providing more outside air to the clients inside, some areas of the shelter are still not consistently capable of meeting the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommendations for outside air supply. Ultraviolet germicidal irradiation (UVGI) fixtures were installed in all of the highest-risk areas of the shelter to help kill or inactivate airborne Mycobacterium tuberculosis. We continue to recommend that all areas of the shelter should be brought into compliance with applicable ASHRAE recommendations for outside air supply. Thorough testing and balancing of the AHUs, along with the proper establishment of setpoints for each AHU, should be completed and documented. Detailed operations and maintenance plans should also be developed to keep the ventilation systems and UVGI fixtures operating properly. Preexisting conditions (prior to September 2003) relating primarily to inadequate fresh air supply and suboptimal filtration of air in the shelter's ventilation systems could have contributed to airborne M. tuberculosis transmission that resulted in the TB outbreak of 2001-2003.
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