3D Printed frames to enable reuse and improve the fit of N95 and KN95 respirators

Abstract

Background In response to supply shortages caused by the COVID-19 pandemic, N95 filtering facepiece respirators (FFRs or “masks”), which are typically single-use devices in healthcare settings, are routinely being used for prolonged periods and in some cases decontaminated under “reuse” and “extended use” policies. However, the reusability of N95 masks is limited by degradation of fit. Possible substitutes, such as KN95 masks meeting Chinese standards, frequently fail fit testing even when new. The purpose of this study was to develop an inexpensive frame for damaged and poorly fitting masks using readily available materials and 3D printing. Results An iterative design process yielded a mask frame consisting of two 3D printed side pieces, malleable wire links that users press against their face, and cut lengths of elastic material that go around the head to hold the frame and mask in place. Volunteers (n = 45; average BMI = 25.4), underwent qualitative fit testing with and without mask frames wearing one or more of four different brands of FFRs conforming to US N95 or Chinese KN95 standards. Masks passed qualitative fit testing in the absence of a frame at rates varying from 48 to 94 % (depending on mask model). For individuals who underwent testing using respirators with broken or defective straps, 80–100 % (average 85 %) passed fit testing with mask frames. Among individuals who failed fit testing with a KN95, ~ 50 % passed testing by using a frame. Conclusions Our study suggests that mask frames can prolong the lifespan of N95 and KN95 masks by serving as a substitute for broken or defective bands without adversely affecting fit. Use of frames made it possible for ~ 73 % of the test population to achieve a good fit based on qualitative and quantitative testing criteria, approaching the 85–90 % success rate observed for intact N95 masks. Frames therefore represent a simple and inexpensive way of expanding access to PPE and extending their useful life. For clinicians and institutions interested in mask frames, designs and specifications are provided without restriction for use or modification. To ensure adequate performance in clinical settings, fit testing with user-specific masks and PanFab frames is required.

Is additive manufacturing a magic bullet to resupply lacking PPE? Producing respirators and face shields during COVID-19 pandemic: A systematic review

“…Most of the analyzed articles were peer-reviewed (excluding the article by McAvoy et al 24 ). There are concerns about the technical aspects of AM in this field, in particular FDM, as it was the dominant technology in the analyzed articles.…”

“…Parameters that were taken into account during face mask analyses included qualitative fit testing, 24 quantitative fit testing, 19,22,43 filtration efficiency, 13,21 and overall comfort or discomfort (Table 3). 18,19,43 It is worth emphasizing that the use of 3D face scanning techniques allows for producing a mask with the highest degree of adhesion, and thus, tightness.…”

The personal protective equipment fabricated via 3D printing technology during COVID-19

“… Antimicrobial mask FDM [ 30 , 31 ] 5. N95 respirators similar FDM [ 29 , 32 ] 6. Nasopharyngeal swabs FDM, SLA, SLS [33] , [34] , [35] 7.…”

Aging of 3D Printed Polymers under Sterilizing UV-C Radiation

“…These prototypes passed OSHA-certified quantitative respiratory testing [19]. Another implementation is that of McAvoy et al, who 3D printed frames that can attach to commercial N95 and KN95 respirators, improving their fit [20].…”