Comparing the fit of N95, KN95, surgical, and cloth face masks and assessing the accuracy of fit checking

Abstract

Introduction The COVID-19 pandemic has made well-fitting face masks a critical piece of protective equipment for healthcare workers and civilians. While the importance of wearing face masks has been acknowledged, there remains a lack of understanding about the role of good fit in rendering protective equipment useful. In addition, supply chain constraints have caused some organizations to abandon traditional quantitative or/and qualitative fit testing, and instead, have implemented subjective fit checking. Our study seeks to quantitatively evaluate the level of fit offered by various types of masks, and most importantly, assess the accuracy of implementing fit checks by comparing fit check results to quantitative fit testing results. Methods Seven participants first evaluated N95 and KN95 respirators by performing a fit check. Participants then underwent quantitative fit testing wearing five N95 respirators, a KN95 respirator, a surgical mask, and fabric masks. Results N95 respirators offered higher degrees of protection than the other categories of masks tested; however, it should be noted that most N95 respirators failed to fit the participants adequately. Fit check responses had poor correlation with quantitative fit factor scores. KN95, surgical, and fabric masks achieved low fit factor scores, with little protective difference recorded between respiratory protection options. In addition, small facial differences were observed to have a significant impact on quantitative fit. Conclusion Fit is critical to the level of protection offered by respirators. For an N95 respirator to provide the promised protection, it must fit the participant. Performing a fit check via NHS self-assessment guidelines was an unreliable way of determining fit.

One size fits all?: A simulation framework for face-mask fit on population-based faces

“…Experimental studies with human subjects and manikins show that mask usage can limit the droplet and airborne transmission of various infections to and from the wearer [8][9][10][11][12][13][14][15][16]. Air leakage has been observed around the perimeter of the mask where it does not make a seal with the face, reducing the effectiveness of the mask [6,17]. Perimeter leakage is caused by loose or improper fitting face masks and can be significantly impacted by facial features [18][19][20][21].…”

“…Perimeter leakage is caused by loose or improper fitting face masks and can be significantly impacted by facial features [18][19][20][21]. A recent study found that seemingly insignificant facial features have an impact on the fitting of the mask on the face and concluded that 3D models could be used to assess mask fit in relation to the subtle changes in facial topology [17]. While proper-fitting of respirators on a face has always been stressed for effective filtering of all contaminants, there is a lack of knowledge on how important the fit of homemade cloth and simple surgical masks is.…”

The Ultra Fit Community Mask - Toward Maximal Respiratory Protection via Personalized Face Fit

“…While improving face mask fit increases protection for both the community and individual (18), the most prevalent type of commercially available mask, disposable multi-layer face masks, such as 3PM, are plagued by poor fit issues (19). To address these persistent design challenges, we have developed a low-cost highperformance mask suitable for mass production and widespread community adoption.…”

Development of a Virtual Fit Analysis Method for an Ergonomic Design of Pilot Oxygen Mask

“…Lastly, Zhuang et al [13] used five 3D head forms representing U.S. workers in designing an industrial respiratory mask. However, the validation of a design with a large group of users is often limited due to time and cost [17][18][19]; therefore, a computerized method would be a practical solution for design validation with a large number of virtual individuals [20,21].…”