Factors Affecting the Location and Shape of Face Seal Leak Sites on Half-Mask Respirators

Abstract

While there have been a number of studies on the effect of leak site and shape on the magnitude of measured leakage through respirator face seals, there have been very few studies to identify the location and size of these leaks. In a previous study we used a method of identifying the location and shape of respirator leaks on a half-mask respirator by the deposition of a fluorescent tracer during a fit test, and testing for their association with facial dimensions. The purpose of this study was to apply that methodology to conduct multiple fit tests to determine if gender, respirator brand, repeated fit tests, and test exercises affected the location and shape of face seal leak sites. Categorical analysis found that none of these factors had a significant effect on the location and shape of leaks. General linear model analysis found some significant effects of the study factors on leaks, but facial dimensions had a greater effect, and there were significant differences between facial dimensions of subjects with a leak and those without. Significant differences in leak site distributions between this and the previous study may have been due to differences in facial dimensions and racial/ethnic composition. Twice as many diffuse leaks as point leaks were observed in both studies, indicating that slit-like leaks would be most appropriate on mannequins used in laboratory respirator leakage studies, and in respirator flow and penetration models. That the study factors had no significant effects in the categorical analysis, significant effects for facial dimensions were found in the linear analysis, and leak site distribution differences between this and our previous study may have been affected by differences in facial dimensions, indicate that, in addition to size, the shape of an individual's face may be an important determinant of leak sites on a half-mask respirator. This would have implications for the design of respirator facepieces and in the selection of respirators for individual wearers.

Manikin-Based Performance Evaluation of Elastomeric Respirators Against Combustion Particles

“…This further suggests that sealing the nose area (rather than the chin area) reduced penetration on average from approximately 5-11% (unsealed) to 0.11-0.48% (nose-only sealed) for the cyclic flow regime, and from approximately 44-51% (unsealed) to 0.66-1.19% (nose-only sealed) for the constant flow regime. This finding is consistent with other studies (30)(31)(32) that suggest the nose is frequently the primary leak location. c. Penetration pathway.…”

“…(30)(31)(32) In the present study, four sealing conditions ("unsealed," "nose-only sealed," "nose and chin sealed," and "fully sealed") were used when testing the half mask respirator. For the full facepiece respirator, only two sealing conditions (unsealed and fully sealed) were used because our pilot study revealed that these two conditions produced similar penetration levels, which made it unnecessary to evaluate partially sealed conditions.…”

Penetration of Fiber Versus Spherical Particles Through Filter Media and Faceseal Leakage of N95 Filtering Facepiece Respirators with Cyclic Flow

“…(7) Roberge et al (15) have shown that nasal and cheekbone regions account for 71% of identified faceseal leaks with three models of N95 FFRs. Furthermore, Oestenstadt and Bartolucci (16) showed that diffuse leaks are twice more common than point leaks. The experiments simulated respirator wearer exposure to elongated particles of various lengths, including fibers.…”

Evaluation of Full-Facepiece Respirator Fit on Fire Fighters in the Municipality of Jeddah, Saudi Arabia

“…Face periphery lines, folded skin, fatty cheeks are important factors in determining fitness of respirators, since they constitute the geometrical contact between face and respirator. It is not a matter of respirator size, but a matter of adjusting the borders of the respirator to the periphery of the faces to reach maximum sealing [12,13,25]. …”