Respirator specialists, manufacturers, and OSHA recognize that cup-shaped, disposable masks have up to 10% (55,56) to 20% (57,58) face-seal leakage even after passing a fit test performed by a qualified individual. This inevitable leakage past face seals results from inherent limitations in the design and construction of these masks. This amount of leakage is unacceptable for effective and reliable respiratory protection against aerosolized droplet nuclei.
What is more relevant, the face-seal leakage for cup-shaped, disposable masks can be considerably higher than 10% to 20% if these masks are not properly fitted to each wearer's face, fit tested by a qualified individual, and then fit checked by each wearer before each respirator use. Both fit testing and fit checking are essential elements in any effective and reliable personal respiratory protection program (55,57,89) as summarized in Table 1 on page 20. At this time there are no NIOSH-recommended qualitative or quantitative fit tests for these masks (81,82). Cup-shaped, disposable masks cannot be reliably fit checked be wearers (58). Therefore, the efficacy and reliability of the face seals on cup-shaped, disposable masks are undependable because there are no proven reliable fit tests nor reliable fit checks. Such devices cannot be relied upon to assure protection of workers against exposure to aerosolized droplet nuclei containing tubercle bacilli.
Another major problem that can contribute to hazardous face-seal leakage of cup-shaped, disposable masks is that in almost all cases these masks are available in only one size. This contrasts with the elastomeric facepieces used for powered, HEPA-filter, halfmask respirators and positive-pressure, air-line, halfmask respirators, which are available in up to three different sizes to fit small, medium, and large facial sizes. The single size in which cup-shaped, disposable masks are available tends to produce higher leakage for wearers with small face sizes (e.g., women, Hispanics, Asians) (96).
Table 2 starting on page 29 summarizes the substantial differences in protection efficacy and reliability between three categories of respirators, which have been considered for protection of health-care-facility workers potentially exposed to tuberculosis.
