Page:Niosh tb guidelines.pdf/39

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Table 2—Summary Comparison of Three Respirator Categories Evaluated for Protection of Health-Care-Facility-Workers Potentially Exposed to Tuberculosis

CONSIDERATION	Surgical Masks Not Certified by NIOSH as Dust and Mist Masks	Cup-Shaped, Disposable-Mask, Particulate Respirators (PRs) Certified by NIOSH	Powered, HEPA-Filter, Halfmask Respirators and Postitive-Pressure, Air-Line, Halfmask Respirators Certified by NIOSH
EFFICACY OF PROTECTION   Face-Seal Leakage	Under optimal use conditions, up to 10% to 20% face-seal leakage is likely for any respirable aerosol (i.e., less than 10 micrometers aerodynamic diameter). Considerably more than 10% to 20% face-seal leakage is possible, since these masks cannot be properly fitted to each wearer's face with fit tests and fit checks.   Face-seal efficacy with these masks is uncertain, since there are no proven fit tests for them and they cannot be fit checked. Current standard tests for these masks do not address either face-seal leakage or the effect that prolonged use might have on this hazardous leakage. Only one facepiece size is generally available that tends to produce higher leakages on small facial sizes (e.g., women, Hispanics, Asians).	Under optimal use conditions, up to 10% to 20% face-seal leakage is expected for any respirable aerosol (i.e. less than 10 micrometers aerodynamic diameter). Considerably more than 10% to 20% face-seal leakage is possible, since these masks cannot be properly fitted to each wearer's face with fit tests and fit checks.   Face-seal efficacy with these masks is uncertain, since there are no proven fit tests for them and they cannot be fit checked. These NIOSH-certified masks are not NIOSH tested for hazardous face-seal leakage during the certification process.   Only one facepiece size is generally available that tends to produce higher leakages on small facial sizes (e.g., women, Hispanics, Asians).	Up to 2% face seal leakage under routine use conditions for any respirable aerosol (i.e., less than 10 micrometers in aerodynamic diameter).   Less than 2% seal leakage can be routinely expected, sine these respirators can be properly lined to each wearer's face with fit tests and fit checks. The screening cutoff value in quantitative fit tests can be adjusted to assure very low faceseal leakage considerably less than 2%. Face-seal efficacy with these respirators is predictable, since they can be both fit tested and fit checked. These NIOSH-certified respirators have been NIOSH tested for their face-seal efficacy during the certification process.   Up to three halfmask sizes are generally available to fit a wider range of facial sizes including small faces.
Filter Leakage	Filter leakage of 25% to 85% has been reported at 30 L/min over the size range 1 to 5 micrometers aerodynamic diameter. Filter efficacy has not been adequately evaluated against droplet nuclei.	Filter leakage of 0% to 40% has been reported at 30 L/min over thes size range 1 to 5 micrometers aerodynamic diameter. Filter efficacy has not been adequately evaluated against droplet nuclei.	HEPA filters are NIOSH-certified to exhibit less than 0.03% filter leakage against any size aerosol. These filters do not need to be tested specifically against droplet nuclei. With air-line respirators, no filter leakage can occur, since no filters are used in these devices.