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The Centers for Disease Control and Prevention recently developed recommendations for respirators worn to minimize exposures to Mycobacterium tuberculosis. These recommendations include criteria for filters and facial fit, but do not address how respirators are worn or disposed of. Handling may increase the risk of infection if loaded organisms remain viable.Respirator filters were challenged with aerosols containing three bacteria: Mycobacterium abscessus, Staphylococcus epidermidis, and Bacillus subtilis subsp. niger. Elution and surface contact sampling were used to recover organisms from filters after loading and following 5 days storage at 85% RH.Almost all filters showed culturable organisms immediately after loading. After storage, filters showed the least culturability for M abscessus (20% of all filters) followed by S. epidermidis (61%), while B. subtilis remained highly culturable (98%). A slimilar trend was seen for the number of organisms recovered before and after storage (M abscessus demonstrated the least survival and B. subtilis the most).

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A method for selecting respirators for protection in infectious aerosol environments was developed, building on a procedure used to choose respiratory protection for environments containing nonbiological contaminants. Modifications in the traditional respirator selection method are proposed for situations where information on occupational exposure limits, toxicity, and airborne concentrations is absent. Toxicity is determined from risk rankings proposed by a variety of organizations. The nature of the activity allows assessment of source generation, which is combined with room volume and airflow to obtain a ranking of airborne concentration. Finally, concentration and toxicity ranks determine a minimum assigned protection factor, which corresponds to a respirator class. Case studies are presented to illustrate the proposed decision logic. For each situation, the procedure yielded choices that were both protective and reasonable. These results suggest that the procedure will be applicable to a variety of settings for a range of infectious organisms.