This type is preferred because the system prevents contaminated air from being recirculated to other areas of the health-care setting. In a single-pass air system, 100% of the supplied air is exhausted to the outside after passing through the room. The two types of ventilation systems are single-pass ventilation systems and recirculation systems. However for natural ventilation control over direction of airflow is difficult and there is no easy-to-use tool for measuring ACH, because natural ventilation is climate dependent 6. In contrast to negative-pressure mechanical ventilation, which is expensive to install and maintain and offers limited protection, natural ventilation may provide greater protection for little cost. A study in Peru showed that natural ventilation achieved more than 17–40 ACH, while well functioning mechanical ventilation in isolation rooms achieved 12 ACH 12. Natural ventilation, such as keeping windows open on opposite sides of the room, could be more effective than mechanical ventilation. American Institute of Architects guideline recommends minimum ventilation rates of two ACH in patient corridors, six ACH in patient rooms, and 12 ACH in AIIR, protective environment rooms, bronchoscopy rooms, and emergency department waiting areas 11. Another study including 17 hospitals in Canada showed that for non-isolation rooms, ventilation rates lower than two ACH were associated with higher tuberculin skin test (TST) conversion rates among HCWs 10. In a modeling study performed in South Africa, improvements to natural ventilation could prevent average of 33% of XDR-TB cases (range, 8%–35% due to wind patterns) 8. ![]() Previous studies investigated the effect of ventilation on TB infection control. The air velocity at the patient's breathing zone of partial enclosures should be kept above at least 200 feet per minute (FPM) to capture droplet nuclei 7, 9.Ī higher ventilation rate is able to provide a higher dilution of airborne pathogens and consequently reduces the risk of airborne infections. Air is drawn across the patient's breathing zone and HEPA-filtered, then discharged back into the room or exhausted outdoors directly. Partial enclosures do not fully enclose the patient. Complete enclosures should have sufficient airflow such that at least 99% of airborne particles can be removed during the interval between turnover of room air. Air from complete enclosures is HEPA-filtered and then can be exhausted outdoors or returned to the room. There are two basic types of local exhaust devices: complete enclosures (e.g., booths or tents) and partial enclosures (e.g., hoods). If LEV is not feasible, cough-inducing and aerosol-generating procedures should be performed in a room that meets the requirements for an airborne infection isolation room (AIIR) 7. Guidelines recommend the use of LEV for cough-inducing and aerosol-generating procedures. LEV is a source-control technique used for capturing airborne contaminants before they disseminate into the general environment. This review provides an overview of environmental control and personal protection. The synergistic combination of available nosocomial infection control strategies could prevent nearly half of extensively drug-resistant (XDR)-TB cases, even in a resource-limited setting 8. ![]() These strategies are synergistic in efficacy when combined. Personal respiratory protection includes the use of respiratory masks 6, 7. Environmental control reduces the concentration of airborne infectious droplets nuclei. Administrative control decreases TB exposure risk by rapid detection, isolation, and treatment of TB patients. Guidelines suggest a three-level hierarchy of controls including administrative control, environmental control, and personal protection. ![]() TB infection control is a combination of measures designed to minimize the risk of TB transmission within populations. ![]() World Health Organization (WHO) reports have described a 5.7 times greater risk of LTBI and TB disease among HCWs than among the general population in low income settings, and 10 and 2 times higher, respectively, in high income settings 6. The incidence of latent TB infection (LTBI) and TB disease among health care workers (HCWs) exceeds that among the general population. Nosocomial transmission of TB occurs in both developed and undeveloped countries, particularly in patients with human immunodeficiency virus 4, 5. TB outbreaks have long been reported in congregate settings including hospitals 1, prisons 2, and homeless shelters 3. Tuberculosis (TB) infection control remains a public health priority.
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