EVALUATION OF SINGLE-USE MASKS AND RESPIRATORS FOR PROTECTION OF HEALTH-CARE WORKERS AGAINST MYCOBACTERIAL AEROSOLS

Background: The recent increase in multidrug-resistant tuberculosis ha s spawned a major controversy concerning the degree of respiratory pro tection needed by health care workers, particularly during sputum-indu cing procedures. The objective of this study was to measure the filtra tion efficiencies of a single-use submicron surgical mask, two disposa ble dust/mist respirators, a dust/mist/fume respirator, and a high-eff iciency particulate air respirator against aerosolized mycobacteria. F acial fit was not addressed. Methods: In a specially designed enclosed test apparatus, an aerosol was generated with a Collison nebulizer fr om a known concentration of Mycobacteria chelonae, used as a surrogate for Mycobacterium tuberculosis. Aerosol concentrations were measured with Andersen samplers upstream and downstream of the test masks and r espirators, which were heat sealed to a metal plate. Results: Mean eff iciencies ranged from approximately 97% for the surgical mask and a du st/mist respirator to more than 99.99% for the high-efficiency particu late air respirator. Measurements of filter efficiency with an Aerodyn amic Particle Sizer for the M. chelonae aerosol and independent challe nge tests with latex spheres correlated closely with measurements of M . Chelonae collection efficiency determined with Andersen samplers. Co nclusions: Analysis of variance and Tukey's method for multiple compar isons indicated that the dust/mist/fume respirator and the HEPA respir ator collected M. chelonae with significantly greater efficiency than did either the surgical mask or the dust/mist respirator. Even the lea st efficient mask tested, however, had a filter efficiency of more tha n 97% against particles averaging less than 1 mum in aerodynamic diame ter.