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

Abstract

Background: In response to supply shortages during 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 often limited by degradation or breakage of elastic head bands and issues with mask fit after repeated use. The purpose of this study was to develop a frame for N95 masks, using readily available materials and 3D printing, which could replace defective or broken bands and improve fit. 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= 41; average BMI= 25.5), of whom 31 were women, underwent qualitative fit with and without mask frames and 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 48-92% (depending on mask model and tester). For individuals for whom a mask passed testing, 75-100% (average = 86%) also passed testing with a frame holding the mask in place. Among users for whom a mask failed in initial fit testing, 41% passed using a frame. Success varied with mask model and across individuals. Conclusions: The use of 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. Frames also have the potential to improve fit for some individuals who cannot fit existing masks. Frames therefore represent a simple and inexpensive way of extending the life and utility of PPE in short supply. 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, qualitative fit testing with user-specific masks and frames is required.

Analysis of SteraMist ionized hydrogen peroxide technology in the sterilization of N95 respirators and other PPE

“…Such studies are important for assessing the real-world implication of mask reuse. Previous work has found that masks subjected to multiple donnings and doffings fail fit testing 36 although potential solutions to this problem have been proposed 37 . Additional questions that must be addressed by real-world testing include inhalation resistance for an N95 mask that has been loaded with internal and external contaminants, the comfort level of health care workers in using an N95 mask that is sterilized but previously used by another individual, and the rate of wastage arising from breakage of elastic bands, and contamination with makeup or topical face products.…”

3D‐Printing to Mitigate COVID‐19 Pandemic

“…Replacing defective or broken bands by 3D‐printed frames ensured a longer lifetime of masks in the case of both N95 and KN95 masks and also proved to be a better fit for the user. [ 77 ] CERN, the European Organization for Nuclear Research, followed all the regulatory and safety specifications similar to the surgical type I mask, to design 3D‐printed flexible and washable masks with replaceable filters. [ 78 ] They also developed an alternative for 3D printers that lacks the capacity of printing flexible items, by separately printing a mould injected with silicon in a rigid plastic material.…”

A Crisis-Responsive Framework for Medical Device Development Applied to the COVID-19 Pandemic

“…Because manufacturing N95-type respirators requires highly specialized fabrics and equipment, it is more feasible to fix the problems with existing masks than to make new ones. As a result, multiple groups have developed 3D printed mask frames that can fit over existing N95 masks and take the place of degraded or broken nosepieces and straps ( 21 – 27 ). Like many other innovative products developed to meet emergency needs, mask frames may also have a role in respiratory protection under non-crisis conditions.…”