This document outlines a possible solution for PPE shortage during the COVID-19 pandemic, specifically focusing on a face mask, or respirator, with a high-grade filtration and fit, comparable to standard N-95 respirators.
The focus of this document is on (1) the fabrication of a fabric-based mask based on easily accessible surgical sterilization wrap, and (2) two different designs for simple assembly with minimal access to specialized material and for scaling up using basic prototyping techniques using laser cutting.
This product is a surgical mask. Materials that contact the body are polypropylene Halyard Sterilization Wrap, polypropylene Medline Sterilization Wrap, and elastic bands. This surgical mask meets Class I or Class II flammability requirements per 16 CFR 1610. Use this surgical mask with appropriate personal protective equipment per your institution’s standards. This product meets fluid resistance testing consistent with standard ASTM F1862 Standard Test Method for Resistance of Medical Face Masks to Penetration by Synthetic Blood.
This device has not been tested or qualified for any of the following uses: to prevent or reduce infection or related uses; for antimicrobial or antiviral protection; for radiation protection. It does not provide particulate filtration. Nor has this device been approved by any local, state, or federal agency, including the FDA. This device has not been disinfected or cleaned. Non-sterile.
The Regents of the University of California makes no claims regarding the safety and efficacy of this product. This product is delivered without warranty of any kind, express or implied, including without limitation any warranty of title, merchantability, or fitness for a particular purpose. Use it at your own risk.
As of April 29th 2020, there are now 1 million COVID-19 cases in the United States and more than 50,000 deaths , and these numbers are rising every day. Some of the characteristics of COVID-19 that have led to a pandemic include the relatively long incubation period before the onset of symptoms, infected individuals who are asymptomatic, and the virus’ capability to be highly infectious compared to other coronavirus strains. Among social distancing, refraining from touching one’s face, and either washing hands with soap and water or an alcohol-based hand sanitizer, the CDC has recently also added that Americans wear at minimum a cloth mask when leaving their residence. Although cloth masks provide some form of protection and help prevent the spread of COVID-19, there are numerous data that suggest cloth masks are not sufficient: In fact, one study found 97% penetrability amongst cloth masks.
The alternative would be medical masks such as surgical masks or N95 respirators both of which are scarce resources during the pandemic and should be reserved for frontline clinicians and healthcare workers who come into contact with COVID-19patients. It is important to maintain sufficient medical-grade masks for healthcare providers to protect them, their families, and their non-COVID 19 patients. However, despite recommendations from the CDC to reserve medical-grade masks for healthcare providers, many people in the general population continue to purchase medical-grade masks for their own protection, refusing to donate them to healthcare providers. In fact, the situation has gotten so bad that there are counties such as Los Angeles County that have told their healthcare workers to reuse their mask, which if done incorrectly does more harm than good.
Protection of frontline healthcare workers is not just crucial for their own personal safety, but also to prevent a collapse of the healthcare system via sick healthcare workers who have contracted COVID-19 and are no longer able to work. The CDC was hesitant to give guidelines regarding the public use of masks in order to prevent resource depletion for healthcare workers, but now that they have outlined that wearing at minimum a cloth mask is recommended this puts the resources at risk . During the pandemic, it is still vital for people to go grocery shopping and non-healthcare essential workers are still leaving their houses. Given that people are still leaving their homes for survival reasons such as grocery shopping, it is important that an effective mask is developed for public use that can take the pressure off the resources that are approved for medical use.
An important goal during the pandemic is to protect both the public and frontline healthcare workers by giving healthcare workers priority for FDA approved medical grade masks. The goal of this project is to create a simple mask design that provides quality N95-like protection for public use and potential medical use to alleviate the scarcity of medical-grade masks.
We and others have identified readily available material that filters 99% of particulates according to our tests and manufacturing specifications. We designed a respirator that provides 0.01% particulate penetration during normal breathing which can be deployed for public use, however, in order to enable scaling up future production and distribution more resources are needed.
Our overall goal is to empower anyone in need in California and beyond to readily access quality respirators that enable protection from the Coronavirus. We want the general population to be able to produce, or locally obtain, face masks with filtration and fit as close as possible to the protection warranted by current standards such as the N95 respirators. To provide generalizable access across populations with varying access to tools and materials, we aim to create a number of designs for DIY respirators that can be produced easily and with various local resources such as small-scale 3D printing facilities, easy-to-find filtration material, sewing, casting and other techniques.
Clinical Applicability and Buy-In
We have received positive feedback to continue making these DIY respirators from top leadership within various departments in the UC San Diego Health Systems such as Surgery, the Emergency Department, and Infectious Diseases. Building off the success we have had with this respirators design, we are also working on optimizing the mask shape to universally seal on all individuals’ faces and provide the seal needed for medical-grade protection. The hope here is to also alleviate the stress on resources available for healthcare workers.
Materials & Methods
We describe here two methods of fabricating DIY Surgical Sterilization Wraps Respirators from Halyard or Medline material.
(1) Square sterilization wraps + Aluminum Strip + Velcro
Transpore 3M tape (any tape is fine really)
Method (Total time: 5 minutes)
(2) Butterfly-shaped sterilization wraps + Metal Nose Piece + Elastic Bands
22 gauge Aluminum Sheet Metal
3/16” Elastic band
Product Testing Results
We performed tests on our DIY Surgical Sterilization Wrap respirators for (1) Particulate Filtration and (2) Face Fit using the PortaCount Plus Model 8020 respirator fit tester. This machine test filters by launching an aerosol at the test filter and measures the number of particulates that get through the filtration substrate.
The particle count is performed using a continuous-flow Condensation Nucleus Counter - a process that grows submicron particles into particles large enough for measurement. This is done by mixing the aerosol with an alcohol vapor so that the alcohol molecules condense into droplets around the molecules of aerosol that have passed through the filtration substrate. The alcohol droplets are then collected on a screen and measured by scattering a laser on the particles and using a photodetector to measure pulses in the incident light - counting pulses counts the number of particles passing through the screen in a given time.
Combining this with a flowrate allows for the calculation of the number of particles per volume. The PortaCount machine is sensitive to particle diameters of 0.02 microns, but cannot distinguish between shapes and structures.
(1) Filtration Test
We tested both the Medline and the Halyard material to verify their filtration efficiency and performed 2 controls (1 with no filter, and one with a HEPA filter that filters out 100.00% of particulates) to verify the machine was functioning. Below are the results of our tests
(2) Face Fit test
Fit TestsFit testing is performed by measuring the number of particulates in the ambient air and comparing that number to the number of particles inside the mask while it is worn. This is done by creating a hole in the surface of the mask and sealing tubing to this hole. The tubing returns to the PortaCount for measuring the number of particles inside of the mask while the wearer performs a series of exercises.
Partial fit tests (only tested fit while breathing at rest) were performed on all of our masks in addition to a full fit test (7 exercises) performed on our Velcro-based DIY mask (1 user), and our laser-cut DIY mask (5 users). We also performed a standard-fit test on the laser-cut DIY mask (5 users).
The table below reports on our test results
Comparing DIY masks to N95 and Surgical Mask
While standing and breathing normally, a certified N95 mask was compared to our DIY surgical wrap mask.
We measured the number of particles inside of the masks and showed that on average, our mask out-performs or is comparable to N95 masks.
While full tests were not performed on our other masks, the brief testing indicated that some of our DIY masks were performing better or close to N95 masks.
The presented DIY Surgical Sterilization Wrap Respirator can be fabricated from common sterilization material from Halyard © and Medline ©, double-sided tape, and metal strips.
We showed two techniques to create a DIY respirator by leveraging either only simple manual manipulations or by using a laser cutter to scale up and described step-by-step instructions on how to produce and then assemble respirators built from these materials.
Our DIY Surgical Sterilization wrap has been shown to a variety of clinicians at UC San Diego Health, specialized in Infectious Diseases, Emergency Department and SUrgery, and all agreed about the potential use of these respirators. In addition, we performed qualitative standard-fit tests and quantitative particulate tests of both material and respirators, and our preliminary work showed that these can filter 99% of particulates the size of the Coronavirus, and can sometimes provide a better fit than some standard N95-mask.
All in all, our DIY respirators can be fabricated with material easily found online, or in standard healthcare facilities, are easy to assemble in a short time, and show a filtration and fit comparable to N-95 masks. However, our masks are not FDA-approved, not have been approved by UC San Diego Health for any clinical use. While we do not have enough evidence to show N95 equivalent or greater protection with high consistency, there is overwhelming evidence to say the mask is more protective than a common surgical mask.
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- Halyard ® *POWERGUARD* Technology, https://www.halyardhealth.com/solutions/surgical-solutions/sterilization-solutions/sterilization-wrap.aspx
- Medline ® Dual Color Bonded Surgical Instrument Wraps, https://www.medline.com/product/Dual-Color-Bonded-Surgical-Instrument-Wraps/Sterilization-Wraps/Z05-PF77587
- Willeke, K., H.E. Ayer, J.D., “New Methods For Quantitative Respirator Fit Testing With Aerosols,” American Industrial Hygiene Association Journal, Feb 1981
- Amy Price, DPhil (Oxon) and Larry Chu, MD On behalf of the Stanford AIM Lab and Learnly COVID-19 Evidence Service Stanford Anesthesia Informatics and Media Lab, "Can face masks be safely disinfected and reused?", https://elautoclave.files.wordpress.com/2020/03/stanford-2020.pdf
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- Walmart Inc, Smooth-On Silicone Mold Making, Liquid Rubber OOMOO 30 Easy to Use, https://www.walmart.com/ip/Smooth-On-Silicone-Mold-Making-Liquid-Rubber-OOMOO-30-Easy-to-Use-Trial-Size-2-8-lb/
Author and Reviewing Information
Authors and Contributors:
Reviewed by: Nadir Weibel, Ph.D., Associate Professor of Computer Science at UC San Diego
Review Date: April 27, 2020
Reviewed by: Eliah Aronoff-Spencer, M.D., Ph.D., Division of Infectious Diseases and Global Public Health, UC San Diego
Review Date: April 30, 2020