Disposable face masks are crucial for protecting against airborne contaminants like viruses and pollutants. While N95 respirators have regulated fit standards, data on the FFE of commonly worn ear-loop masks (KN95, surgical, KF94) is limited. The COVID-19 pandemic and increasing wildfire smoke exposure have increased public mask use, highlighting this data gap. Mask efficacy depends on both material and fit. Several modifications have been proposed to improve fit and reduce leakage. This study aims to quantify the variation in FFE of these commonly worn masks, comparing them to N95 respirators and assessing the impact of a simple ear-loop clip modification on FFE, specifically investigating sex-based differences.

Previous research has shown variations in mask protection due to factors like design, materials, and individual wearer characteristics (facial hair, fit). Studies have examined the effectiveness of cloth masks and modified procedure masks, but data on the common ear-loop styles worn by the general public is scarce. Prior work has also investigated methods to improve mask fit, including double masking and modifications to improve the seal against the face. The limited data on the FFE of commonly available masks during the COVID-19 pandemic motivates this study, seeking to address the lack of information on the efficacy of different masks and fit improvement strategies.

One hundred healthy adults (50 female, 50 male; average age 32.3 ± 9.2 years; average BMI 25.5 ± 3.4) participated. Participants underwent a modified OSHA Quantitative Fit Test using four mask types: N95, KN95, surgical, and KF94. Ear-loop masks were also tested with a clip modification. FFE was calculated as (100 × [1− particle number in breathing space behind mask / particle number in ambient chamber air]). Mixed-effects linear regression analyzed FFE, considering mask type, sex, and clip modification as fixed effects and participant as a random effect. Sensitivity analysis included age, BMI, and race/ethnicity. Pairwise t-tests and post-hoc Tukey tests compared sex differences and the effect of the clip modification.

The N95 respirator showed the highest FFE (97.8% ± 3.2%). Significant sex differences in baseline FFE were observed for KN95, surgical, and KF94 masks. Males had significantly higher FFE than females (−7.4% for KN95, −10.1% for surgical, −15.2% for KF94). The clip modification significantly increased average FFE overall (6.4%), but the improvement varied by sex. Females experienced a larger increase (20%) than males (6%). The largest increase in modified FFE was observed with the KF94 mask for female participants (+26.1%). The effect of the clip was more pronounced for participants with lower baseline FFE, suggesting that the clip modification may be more beneficial for those with a poorer initial mask fit. Sensitivity analysis showed that age and BMI were significant confounders, but their inclusion did not alter the main findings regarding sex differences in FFE and the effect of the clip modification. The KN95 mask was the only condition that consistently exceeded the FFP1 threshold for filtration after the clip modification.

This study reveals significant sex-based differences in the FFE of commonly used ear-loop masks. Males consistently showed higher baseline FFE than females. The simple clip modification effectively improved FFE, particularly for females, potentially acting as a fit equalizer. The observed sex-based disparity in FFE likely relates to differences in craniofacial morphology. This finding has important public health implications as it highlights the variability in protection offered by these masks and suggests targeted interventions to optimize mask fit and improve protection, especially for women. This study also highlights the importance of considering the impact of simple modifications on mask performance.

This study demonstrated significant sex-based differences in the FFE of commonly worn disposable face masks. Males had higher baseline FFE than females for KN95, surgical, and KF94 masks. A simple ear loop clip modification significantly improved FFE, particularly for females. Future research should investigate the relationship between craniofacial morphology and mask fit, informing strategies for improved mask design and fit modifications.

This study used only one model and manufacturer for each mask type, limiting generalizability. The study population was restricted in age and BMI, and included only healthy participants, potentially limiting generalizability to broader populations. Further research should include larger and more diverse populations, encompassing a wider range of ages, BMIs, and mask manufacturers.