Guidance Document for Manufacturing Masks and Respirators for protection against COVID-19 Updated May 21, 2020 The purpose of this document is to provide open source guidance, resources, references, ideas, and information to improve the manufacturing of DIY masks. The ultimate goal is to make recommendations on best materials and manufacturing methods for a variety of technical and non-technical capabilities. We welcome your collaboration. Document originators: Jeffrey Ott, Biorez Jacob Komenda, Biorez Justin Bendigo, Biorez Kevin Rocco, Biorez Document collaborators: Michael Plumley, Ph.D, P.E., US Coast Guard Academy Christopher Wiles, D.O., UConn Anesthesiology BIOREZ, INC 1: Purpose of this Guidance Document 2 2: Role of PPE & Transmission Mechanisms of COVID-19 3 2.1: Transmission Mechanisms of COVID-19 3 2.2: What is a Mask versus a Respirator? 4 2.3: How Masks and Respirators Work? 6 3: Guidance for Make-at-Home Masks 9 3.1: Purpose of Masks and User Needs 9 3.2: Overview of Primary, Secondary and Tertiary Mask Structure 10 3.3: Types of Fiber (Primary Structure) 10 3.4: Types of Fabric (Secondary Structure) 13 3.4.1: Commercially Available Material Table 17 3.4.2: Expanded Section on Materials 19 3.4.2.1: Fabrics 19 3.4.2.2: Other Materials 20 3.5: Mask Assembly (Tertiary Structure) 22 3.5.1: Design Features 22 3.5.2: Design Criteria 25 3.5.3: Published Methods of Assembly 25 3.5.4 Other Manufacturing Methods 27 3.6: Tips for Fit, Function, Cleaning & Re-Use 30 3.7: Lab Testing and Regulatory 32 4: Other Teams, Projects and Resources to Consider 35 APPENDIX A - SEM Imaging 36 APPENDIX B - Filtration Efficiency Figures 36 APPENDIX C - www.n95decon.org 43 APPENDIX D - Overflow 48 D.1: Polypropylene Background and Usage in Respirators 48 D.2: Production Techniques and Tips 49 D.3: N95 Respirator Testing Expanded 51 < Initially prepared by BIOREZ for open source distribution and collaboration > 1 BIOREZ, INC < Initially prepared by BIOREZ for open source distribution and collaboration > 2 BIOREZ, INC Executive Summary The COVID-19 virus is primarily transmitted between people through respiratory droplets and contact routes, with airborne transmission still a topic of research. This document provides open ​ source guidance, resources, references, ideas, and information to improve the manufacturing of Do It Yourself (DIY) masks. Discussion of progress toward development of DIY respirators is also discussed. It is intended to be collaborative. Research about the current Covid-19 pandemic is moving at a rapid pace, and this document provides current information regarding materials and manufacturing methods for a variety of technical and non-technical capabilities. Masks and respirators are key PPE for protection against COVID-19, and have different purposes. The CDC recommends that simple masks including cloth face coverings (home-made masks) be worn when in public instead of N95 respirators. A respirator’s job is to filter airborne aerosol droplets from the user’s air supply. Made-at-home masks are not intended to prevent the transmission of Covid-19 but provide a low level of protection and ease of manufacture. Careful selection of materials and methods will lead to higher quality and more effective made-at-home masks without increasing the difficulty of manufacturing. The ideal mask is easy to manufacture, tight fitting, highly breathable, traps and/or deflects particles, and is cleanable and reusable. Mask design may be discussed in terms of primary (fiber type), secondary (fabric type), and tertiary mask structure. While high thread cotton is commonly used, the best mask filters would consiste of mats of nonwoven fibrous materials, such as wool felt, fiberglass paper, and polypropylene. Nonwoven materials are dense, create a tortuous path, and adhesion of particles to the fibers without blocking open porous spaces, allowing air to flow easily. Furnace filter paper and sterilization wrap offer commercial sources for nonwoven materials, and flow properties of these are still being studied and reported in the media. Ideally, a hydrophilic outer ​ layer (such as cotton) canl be used to absorb respiratory droplets, while the hydrophobic inner layer (such as nonwoven furnace filter or polypropylene) prevents droplets from entering the fiber and prevents the trapping of moisture. Mask structure may be created through sewn pleats or form fitted filtration material, or constructed plastic frames or hard shells which hold filter material. They are all often held by some sort of elastic. Respirators are highly regulated. As such, care should be taken when choosing an “N95 replacement”, as strict NIOSH testing procedures have likely not been carried out to ensure the same protection. Hard shelled fitted respirators require testing. Both the development of locally manufactured models through procedures like 3D printed, and methods to test such PPE, are the subject of considerable ongoing study by the DIY community and collaborators. The design space for masks and respirators is rapidly evolving as the SARS-CoV-2 pandemic is met by solutions developed in an unprecedented era of online collaboration and maker < Initially prepared by BIOREZ for open source distribution and collaboration > 3 BIOREZ, INC technology, in a race to eliminate PPE shortages in hospitals and the community. As such, this and other documents will also evolve rapidly to keep pace with innovation. < Initially prepared by BIOREZ for open source distribution and collaboration > 4 BIOREZ, INC 1: Purpose of this Guidance Document Whether working in a supply-limited healthcare environment, or just going to the grocery store, we believe there should be a more scientific approach to manufacturing your own PPE. The purpose of this document is to provide open source guidance, resources, references, ideas, and information to improve the manufacturing of DIY masks. It is intended to be collaborative. Research about the current Covid-19 pandemic is moving at a rapid pace, and this document serves to represent the best of what we know of the situation in real time. The ultimate goal is to make recommendations on best materials and manufacturing methods for a variety of technical and non-technical capabilities. We welcome your collaboration. This document is intended as a primer to discuss the fundamental specifications and testing required for development of Do-It-Yourself (DIY) design and manufacturing of Personal Protective Equipment (PPE) intended to prevent the transmission of or infection with Covid-19 and similar viruses. This document is not intended to provide detailed manufacturing instructions, declare particular designs or processes superior, or to replace accepted Codes or Standards. < Initially prepared by BIOREZ for open source distribution and collaboration > 5 BIOREZ, INC 2: Role of PPE & Transmission Mechanisms of COVID-19 2.1: Transmission Mechanisms of COVID-19 According to the WHO, SARS-CoV-2, commonly referred to as Covid-19 or novel ​ coronavirus, is primarily transmitted between people through respiratory droplets and contact routes. Currently there are three mechanisms of transfer being investigated in relation to the ​ Covid-19 outbreak: Respiratory droplets, airborne transmission, and contact routes.(WHO ​ ​ ​ ​ ​ ​ Scientific Brief Modes of transmission of virus causing COVID-19: implications for IPC precaution ​ recommendations​) Respiratory droplets originate from an infected person sneezing, coughing, spitting, etc. They can be in the form or water vapor or mucus droplets that are expelled from the infected individual. These droplets are 5-10 microns large and are currently believed to be the primary transmission mechanism of COVD-19. Transmission occurs when someone comes into direct contact with these droplets and they get into the mouth, nose, or eyes after a cough or sneeze, or through indirect contact when an individual touches their mouth, nose or eyes after touching an object that had respiratory droplets resting on it. Surfaces and objects that transmit the virus are called fomites and droplets may stick around for hours and possibly days after falling there. ​ ​ (WHO Scientific Brief Modes of transmission of virus causing COVID-19: implications for IPC ​ precaution recommendations​) Typically, respiratory droplets do not remain suspended in the air and fall quickly due to their size. Sometimes it may take a couple seconds, sometimes minutes, and sometimes even longer depending on the air flow in a room and the actual sizes of the droplets. The 6 foot radius that has been established as a minimum safe distance for social distancing is based on research of these patterns. However, in reality there is no imaginary wall 6 feet away from a person that prevents further spread droplets. They can likely travel much farther when propelled by an uncovered sneeze or cough. (Turbulent Gas Clouds and Respiratory Pathogen Emissions​) ​ Airborne transmission typically refers to conveyance of virus through respiratory droplets which are under 5 microns in diameter. These originate in a similar manner, being expelled through mechanisms including breathing, coughing and sneezing. These very small droplets are referred to as aerosols or aerosol droplets. Particles of this size can be suspended in the air for several hours or by some accounts, indefinitely. This again depends on the airflow conditions and the actual size of the droplets. Additionally, in some instances, droplets under 5 micron diameter will fall quickly and droplets larger than 5 microns may stay in the air for hours. The < Initially prepared by BIOREZ for open source distribution and collaboration > 6 BIOREZ, INC length of time it takes for a particle or droplet to fall out of the air is referred to as the settling time. (Review of Aerosol Transmission of Influenza A Virus​) ​ It is generally believed that the coronavirus is not airborne, or that it does not transmit through aerosol droplets that remain suspended in the air for long periods of time. This is currently a subject of contention among researchers.