EFFECTIVENESS OF IN-ROOM AIR FILTRATION AND DILUTION VENTILATION FOR TUBERCULOSIS INFECTION-CONTROL

Tuberculosis (TB) is a public health problem that may pose substantial risks to health care workers and others. TB infection occurs by inhal ation of airborne bacteria emitted by persons with active disease. We experimentally evaluated the effectiveness of in-room air filtration s ystems, specifically portable air filters (PAFs) and ceiling-mounted a ir filters (CMAFs), in conjunction with dilution ventilation, for cont rolling TB exposure in high-risk settings. For each experiment, a test aerosol was continuously generated and released into a full-sized roo m. With the in-room air filter and room ventilation system operating, time-averaged airborne particle concentrations were measured at severa l points. The effectiveness of in-room air filtration plus ventilation was determined by comparing particle concentrations with and without device operation. The four PAFs and three CMAFs we evaluated reduced r oom-average particle concentrations, typically by 30% to 90%, relative to a baseline scenario with two air-changes per hour of ventilation ( outside air) only. Increasing the rate of air flow recirculating throu gh the filter and/or air flow from the ventilation did not always incr ease effectiveness. Concentrations were generally higher near the emis sion source than elsewhere in the room. Both the air flow configuratio n of the filter and its placement within the room were important, infl uencing room air flow patterns and the spatial distribution of concent rations. Air filters containing efficient, but non-high efficiency par ticulate air (HEPA) filter media were as effective as air filters cont aining HEPA filter media.