Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, HETA 2013-0110-3218, 2014 Aug; :1-45
On March 21, 2013, the National Institute for Occupational Safety and Health (NIOSH) received a request for technical assistance from the Chief Epidemiologist of the Dallas County Department of Health and Human Services, on behalf of the Executive Director of a large faith-based homeless shelter in Dallas, Texas, which was one of two shelters linked to an ongoing tuberculosis outbreak among homeless people in the Dallas area. The request asked NIOSH to assess the heating, ventilation, and air-conditioning (HVAC) systems and make recommendations to improve overall environmental controls at the shelter. During an on-site evaluation of the homeless shelter in June 2013, we collected physical and ventilation measurements in all key areas of the facility. We focused on areas where shelter guests typically congregate or spend significant amounts of time. We recorded the make and model number of air-handling units (AHUs) providing air to the facility, and visually inspected the units, when possible. We also measured the air flow rate through all supply diffusers and return grilles. Over the last two decades, the shelter has acquired all of the pieces of a former commercial office building. Thus, the shelter inherited HVAC equipment from various manufacturers. We were able to identify ventilation quipment from at least 13 different manufacturers during our assessment (see Table 1). Air-handling units ranged from newer, well maintained systems to old, inoperable systems. Ventilation filters were often missing or installed in incorrect configurations. Certain aspects of the ventilation systems' operation could potentially contribute to airborne disease transmission among shelter guests. Some areas of the shelter were not being served by mechanical ventilation during our visit, because various AHUs were not functional. Additionally, it appeared the AHUs were not providing adequate outdoor air to the occupied spaces, as is required by the Dallas Mechanical Code and ASHRAE standards. In addition to alleviating odors and maintaining occupant comfort, outdoor air serves to dilute infectious aerosols, such as Mycobacterium tuberculosis droplet nuclei that are responsible for TB transmission. Since the TB outbreak began, the shelter has taken numerous steps to improve administrative controls, particularly when it comes to identifying guests showing signs and symptoms of TB. We recommend additional improvements to the administrative and environmental controls at the shelter. From a ventilation standpoint, we suggest that all occupied spaces at the shelter be served by mechanical ventilation and all areas supplied with adequate amounts of outdoor air, as prescribed by the Dallas Mechanical Code and ASHRAE standards. In addition, we identified areas, at least one of which should be converted for respiratory separation purposes. This space could serve to separate a guest suspected of having TB or other respiratory diseases from the remainder of the guest population, until medical evaluation, transport or treatment could be obtained. We also recommend developing a written infection control plan, an HVAC operation and maintenance plan, and a written respiratory protection program. Having these plans/programs in place will help the shelter under normal operating conditions, and especially during future outbreaks of respiratory disease.
Region-6; Infectious-diseases; Infection-control; Respiratory-system-disorders; Bacteria; Bacterial-disease; Bacterial-infections; Ventilation; Ventilation-systems; Heating-equipment; Heating-systems; Air-conditioning-equipment; Air-contamination; Indoor-air-pollution; Indoor-environmental-quality; Disease-transmission; Disease-control; Disease-prevention; Environmental-control-equipment; Environmental-engineering; Environmental-exposure; Engineering-controls; Control-technology; Air-flow; Measurement-equipment; Airborne-particles; Equipment-design; Air-quality; Aerosols; Administration; Humans; Sociological-factors; Quality-standards; Respiratory-protection; Public-health; Germicides; Irradiation;
Author Keywords: Temporary Shelters; tuberculosis; environmental controls; ventilation; homeless shelter; airborne infection; airborne transmission; respiratory