Journal of the International Society for Respiratory Protection

1 | Next-Generation Custom-Fit Reusable Respiratory Protective Device with Continuous Fit Monitoring – Part III: 3D Printing of Prototypes and Evaluation

13 | Abstracts 21st International Conference of the International Society for Respiratory Protection “Respiratory Protection, Use, and Users”

57 | Instructions for Authors

Next-Generation Custom-Fit Reusable Respiratory Protective Device with Continuous Fit Monitoring – Part III: 3D Printing of Prototypes and Evaluation

Sungmee Park1, Yuanqing Tian2, Michael Bergman3, Jonisha Pollard3, Ziqing Zhuang3, and Sundaresan Jayaraman1*

1 Georgia Institute of Technology, School of Materials Science and Engineering

2 Georgia Institute of Technology, School of Industrial Design

3 National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory

*Corresponding author: Sundaresan Jayaraman, sundaresan.jayaraman@gatech.edu, Phone: 404.894.2461

ABSTRACT

Some respiratory protective devices (RPDs) such as filtering facepiece respirators (FFRs) are manufactured in discrete sizes, with some models being limited in accommodating the fit of some gender and race combinations. This study presents the development of a custom-fit RPD which conforms to a user’s facial features and flexes and moves with facial movements during use. Our design also integrates a pressure-sensing network, which continuously monitors fit and will alert the user when the fit is compromised.

In this final part of the three-part series, we transform the digital prototypes of the custom-fit RPD presented in Parts I and II to physical prototypes through 3D printing (additive manufacturing) using silicone-based elastomers. We identify the key material properties required for creating the physical prototypes. Based on a comparative analysis of commercially available materials, we select two of them and create prototypes of the RPD using two different commercial 3D printers. We then demonstrate the responsiveness of the custom-fit RPD to changes in facial profile during use from natural (neutral facial expression with mouth closed) to talking, to smiling, and to yawning, and the quantification of the changes in pressure at the faceseal by the continuous fit monitoring system through an App running on an Android tablet. With the realization of the successful custom-fit RPDs using the developed methodology, we lay the foundation for providing respiratory protection, and improved source control, to the full spectrum of individuals in the United States public including children, for whom FFRs options are currently limited.

Keywords: Custom-fit respiratory protective device; continuous fit monitoring; 3D printing; additive manufacturing, Shore hardness; protection; comfort; faceseal pressure; pressure injury; data analytics; facial profile

Fit testing of respirators with ear loop straps

Nick Baxter*, Helen Beattie, Gillian Nicholls and Duncan Smith

Health and Safety Executive, Science Division, Buxton, Harpur Hill, SK17 9JN, UK

*Corresponding author and email: Nicholas.baxter@hse.gov.uk

ABSTRACT

Background: Due to large demand for respirators during the COVID-19 pandemic, particularly filtering facepiece respirators (FFP) level 3 (FFP3) in Great Britain (GB), an increasing number of FFPs with ear loop straps were imported into GB from outside of Europe. Many of these FFPs were incorrectly and often dually marked, showing a European “CE” (“Conformité Européenne”) mark which indicates conformance with the European standard BS EN 149 for respiratory protective devices (RPD), and a KN95 marking, which shows conformity to the Chinese standard GB 2626-2006 for respiratory protective equipment (RPE).

There is evidence suggesting FFPs with ear loop straps do not pass a fit test on a significant proportion of the intended population, with many studies throughout the world demonstrating a low fit testing pass rate of FFPs with ear loop straps.

Objective: The aim of this study was to evaluate the fit of KN95 style respirators with ear loop straps on volunteers representative of GB users, using a quantitative fit testing method.

Methods: Eight models of respirators with ear loop straps, with no certification documentation, were selected from different manufacturers. Quantitative fit testing using an ambient particle counting method was conducted on 29 volunteers. The order of the fit testing on each respirator was randomised. The study followed the fit testing protocol as described in Health and Safety Executive (HSE) guidance on RPE fit testing, INDG 479.

Results: From the 232 fit tests completed, only one achieved a fit factor above the pass/fail criteria of 100. The data showed a 95% confidence that the geometric mean of the overall fit factors lies between 3.0 and 4.7, and is significantly lower (P<0.05) than the pass/fail criteria of 100. Volunteer comments on the perceived fit of the respirators with ear loop straps included being loose on the face, and feeling leakage around the edges of the respirator. Discomfort of the straps around the wearers’ ears was also described.

Conclusion: The testing confirmed that there is a very low fit testing pass rate for FFPs with ear loop straps. Comments from volunteers also indicated that the perceived fit was poor.

Keywords: COVID-19 pandemic, healthcare, filtering facepiece respirators, ear loop straps, quantitative fit

test, KN95, discomfort, ears.

Human Errors in Qualitative Respiratory Protective Equipment Fit Testing: A Study of Real-World Fit Testers

Karen M. Long1,*, Nathalie Mai1, Michael Williams1

1. Cranfield University, Cranfield Defence and Security, Bedford UK.

* Corresponding author email: karen.long@face-fit.co.uk

ABSTRACT

Background. Fit testing is an essential part of any respiratory protective device program and provides a method for assessing the effectiveness of the face-to-facepiece seal of a tight-fitting facepiece which helps to assure wearer protection. Although qualitative fit test methods are assumed to be simple and easy to use, it remains critical that the methodology is applied in accordance with the protocols set out in guidance to ensure that a correct ‘pass’ or ‘fail’ result is assigned. An incorrectly assigned pass result increases the risk to the wearer of exposure to hazardous respiratory substances in the workplace, putting their health or life in danger. Fit testing stakeholders, manufacturers and regulatory bodies have raised concerns about the quality of fit testing conducted in the UK workplace, but there have been no published research studies in this area to date.

Methods. This article presents results from a study into the errors made by real-world qualitative fit testers, using the data gathered during Fit2Fit practical assessments conducted in the UK over a ten-year period from 2009 to 2019.

Results. When application of the qualitative fit test method was measured against the HSE INDG479 protocol, assessment records indicate that fit testers made a median of 4 errors, and a high of 29 errors. Fit2Fit accredited fit testers appear to make half as many errors as non-accredited fit testers, yet the scheme remains voluntary in the UK. The sources of errors were analysed in detail and revealed that the most common errors were made in instructing the wearer, donning and fit checking RPE, verifying the nebuliser function, and assuring the wearer’s taste detection.

Conclusion. Results from this study suggest that errors made by real-world fit testers are common, and steps to mitigate the assignment of false pass fit test results arising from these errors are needed if wearer health is to be better protected.

Keywords: Qualitative fit test, QLFT, FFP3 respirator, half mask respirator, Fit2Fit, competency.

Minimum oxygen concentration in breathing gas:

Effects of altitude

Dan Warkander1,2,*, Richard Arnold1, Alberto Spasciani3

1. Naval Medical Research Unit Dayton, Dayton, OH, USA,
2. Leidos, Reston, VA, USA,
3. Spasciani Spa, Origgio, Italy.

* Corresponding author email: dan.warkander.1.ctr@us.af.mil, dwarkand@buffalo.edu

ABSTRACT

Background. Oxygen is essential for life and a minimum safe level shall be determined before using air purifying respiratory protective devices. However, no consensus among regulatory standards exists on what is a safe low limit of oxygen concentration (O2%) – the values range from 17% to 19.5%. A person’s fundamental need is the partial pressure of oxygen, not the O2%. The partial pressure of O2 is proportional to the number of molecules of O2 in the air. Since the barometric pressure decreases with altitude, the number of O2 molecules in a breath of air also decreases. Therefore, it makes little sense to express a safe low limit as a concentration, unless the altitude of use is specified. For instance, if an altitude of 2,400 m (8,000 feet) is considered safe when breathing air, the equivalent partial pressure of O2% would be provided at sea level from a gas containing 15.3% O2.

Objective. To highlight the different levels of O2% or altitude that are considered safe in various situations and provide means to determine how the necessary O2% level changes with altitude.

Methods. The alveolar gas equation was used to determine the equivalence between O2% and altitude for a given partial pressure of O2.

Results. The equivalences between O2% and altitude are shown in graphs for easy interpretation. For instance, if it is deemed acceptable to breathe air at 2,400 m, then the equivalent O2% is 19.3% at 1,800 m or 17.3% at 1,000 m. Breathing gas containing 23.5% O2 at an altitude of 3,300 m is equivalent to breathing air at 2,400 m.

Conclusion. The step-by-step approach described will allow a Safety Officer or user of respiratory protective devices to determine equivalent O2% based upon a generally accepted safe condition from a known altitude.

Keywords: partial pressure of oxygen, partial pressure of carbon dioxide, O2, CO2, hypoxia, hyperoxia, alveolar gases.

Desmitificando los FPAs para EPR: intentando lo imposible

(This is a Spanish language translation of a commentary originally published in English language by the ISRP)

Samantha Connell¹*, CIH^[1], Stephanie Lynch, PhD, CSP²

¹Directora de Programas de Salud Global, Indorama Ventures PCL y presidente de la Asociación Internacional de Higiene Ocupacional

²Gerente senior de tecnología e investigación en OHD LLLP y vicepresidente de la Sociedad Internacional de Protección Respiratoria

* Autor correspondiente y correo electrónico:samantha.connell.cih@outlook.com

^[1] Certified Industrial Hygienist (Higienista Industrial Certificada)

RESUMEN

Este comentario tiene como objetivo compartir perspectivas internacionales sobre los equipos de protección respiratoria (EPR) y el concepto de factores de protección asignados (FPA)^[1]. FPA es un valor numérico establecido por una organización que indica el nivel de protección que se debe esperar para la mayoría de la población que utiliza ese equipo de protección respiratoria (EPR), cuando se usa correctamente. Diferentes países y organizaciones tienen diferentes enfoques para establecer los FPA, lo que puede llevar a que exactamente el mismo EPR tenga diferentes valores de FPA en diferentes países. Después de años de navegar por múltiples reglas específicas de cada país (o la falta de ellas), los autores buscaron establecer qué FPA debería aplicarse a empresas como las suyas, que operan a nivel mundial. En este comentario, los autores no llegan a una conclusión específica, sino que comparten la información que obtuvieron a lo largo de su viaje y brindan una discusión sobre la situación global. Los autores se educaron en los Estados Unidos y tienen experiencia laboral internacional, pero no pretenden representar las perspectivas de todos los países con respecto a las FPA.

Palabras clave: equipo de protección respiratoria, factor de protección asignado, factor de protección nominal, normas internacionales

^[1] En ingles APF por “assigned protection factors”. Al traducir se prefirió respetar las designaciones en español.

Demystifying APFs for RPE: Attempting the impossible

Samantha Connell¹*, CIH, Stephanie Lynch, PhD, CSP²

¹Global Health Programs Director, Indorama Ventures PCL, and President, International Occupational Hygiene Association

²Senior Technology and Research Manager at OHD LLLP, and Vice President, International Society of Respiratory Protection

* Corresponding author and email: samantha.connell.cih@outlook.com

ABSTRACT

This commentary aims to share international perspectives on respiratory protective equipment (RPE) and the concept of assigned protection factors (APFs). APF is a numerical value established by an organization indicating the level of protection that should be expected for a majority of the population using that respiratory protective equipment (RPE), when used correctly. Different countries and organizations have different approaches to setting AFPs, which can lead to the same exact RPE having different APF values in different countries. After years of navigating multiple country specific rules (or lack thereof), the authors sought to establish which APFs should be applied for companies like theirs that operate globally. In this commentary, the authors do not come to a specific conclusion, rather they share the information they obtained along their journey and provide some discussion of the global situation. The authors are educated in the United States and have international work experience but do not claim to represent all countries’ perspectives regarding APFs.

Keywords: respiratory protective equipment, assigned protection factor, nominal protection factor, international standards

Respiratory protection for Canadian Armed Forces members with headdress and/or beards: Powered air purifying respirators for interim use in CBRN training

Dr. Paul Bodurtha1*, Dr. Eva F. Gudgin Dickson1,2, Maj. Christian Doucet3

1. Defence Research and Development Canada (DRDC)
2. Royal Military College of Canada (RMC)
3. Canadian Armed Forces (CAF)

* Corresponding author and E-mail: paul.bodurtha2@forces.gc.ca; tel. 403.544.4622; Suffield Research Centre, Defence Research and Development Canada, Box 4000, Station Main, Medicine Hat, Alberta, T1A 8K6

ABSTRACT

Background: The Canadian Department of National Defence (DND) and the Canadian Armed Forces (CAF) are in the process of developing inclusive solutions for chemical-biological-radiological-nuclear (CBRN) respiratory protection for CAF users. The ultimate goal is to provide a variety of low-burden CBRN respiratory protection options for operational use for all wearers, including those with facial hair and/or headdress, as well as other individuals with hard to fit faces in the context of fit testing.

Methods: In this study, the option of providing the in-service C4 and C5 CBRN respirators in a powered air form was investigated for their ability to provide adequate protection in both training and operational contexts, and for training procedures to be suitably adapted and implemented. Their performance was compared to existing requirements for the C5 respirator with regards to their ability to remove airborne contaminants via filtration, and for wearers with beards and/or headdresses, their fit factor in powered air mode, their protection factor in use via simulated workplace protection factor (SWPF) measurements, and their use in a tear gas hut for training.

Results: The flow rate through each of the two C8 filters in the powered air configuration was less than the 50 L/min at which the filters were specified and tested for approval, while the flow rates of the other two filter configurations investigated were similar to the C8. All were demonstrated suitable for use in the study and the C8’s filtration performance in the powered air (PA) configuration would be appropriate for operational use. When fit factors were measured in the PA configuration, all individuals tested achieved a value greater than 10,000. Similarly, in SWPF all individuals obtained overall protection factors of greater than 10,000. Finally, in a training activity in the tear gas hut, all individuals were able to perform the training drills successfully without exhibiting effects from the tear gas.

Conclusion: The C4 or C5 PA configuration is suitable for use in CBRN training in the tear gas hut for individuals with beards and/or headdresses, and shows promise when used with the C8 canister for operational application in a CBRN environment, with further investigation needed to demonstrate meeting all of the operational requirements.

Keywords: chemical-biological-radiological-nuclear (CBRN) protection, beards, facial hair, headdress, respiratory protection, simulated workplace protection factor, CS tear gas, quantitative fit testing, powered air purifying respirator (PAPR).

Assessment of a Novel Low-Cost Personal Respirator Evaluation Device

Quinton F. Burke M. Eng.*, Kevin Aroom M.S., P.E., and Martha O. Wang Ph.D.

Robert E. Fischell Institute for Biomedical Devices, 5102A A. James Clark Hall, 8278 Paint Branch Drive, University of Maryland, College Park, MD 20742

* Corresponding author and E-mail: qburke@umd.edu

ABSTRACT

Background: Throughout the COVID-19 pandemic, respirators and masks have been recommended, and in many instances mandated, across the globe. The National Institute for Occupational Safety and Health (NIOSH) is the main regulatory agency for respirators in the United States. Currently, the TSI 8130A and the ATI 100Xs machines are utilized for respirator filtration and resistance testing, but both are costly and valued upwards of U.S. $100,000.

Objective: The goal of this study was to develop a low-cost respirator evaluation mechanism (LREM) to evaluate respirators as well as masks and other materials for filtration efficiency (FE), inhalation resistance (IR), and exhalation resistance (ER). The aim of this mechanism is to support the development of innovative and alternative respirator and mask designs and materials with an inexpensive and more accessible testing device.

Methods: The methods and design for the LREM were based on U.S. 42 CFR Part 84 Subpart K and the corresponding standard testing procedures for air-purifying respirators published by NIOSH. The LREM itself is constructed from available components and functions to deliver sodium chloride (NaCl) aerosols in a stream of airflow to challenge a respirator or mask sample. A variety of respirators, masks, and materials were tested on both the LREM and an ATI 100Xs to assess how the LREM compares to one of the current evaluation devices.

Results: Overall, the LREM offers promise as an accessible and low-cost testing option. The LREM can accurately determine the pass/fail status of the N95 filtering facepiece respirators (FFRs) samples tested for both IR and FE based on NIOSH criteria. For all respirators, masks, and materials tested, the LREM and ATI 100Xs both show similar performance trends as seen by rankings of sample performance.

Conclusions: The LREM was constructed for approximately 6% the cost of current respirator testing gold standards. The LREM could serve as a first pass testing method done before official respirator testing (e.g. per NIOSH mandated testing) and can be particularly useful in the development of innovative respirators and masks or in testing alternative materials for each.

Keywords: COVID-19, respirator, mask, respirator testing, filtration efficiency, inhalation resistance, exhalation resistance.

Demonstration of a Reusable Mask in a Tubular Design that Provides Universal Fit and Protection from Respiratory Hazards

Chris Baglin¹, Axel Bawor¹, Mia Burleigh², Claire Chalmers², Chris Easton², Fiona Henriquez², William Mackay², and Paul Baglin¹

¹ tensARC, Unit 27, STEP, Stirling, FK7 7RP, Scotland

² University of the West of Scotland

* Corresponding author and E-mail: paul@tensarc.co.uk

ABSTRACT

Background: There is a well-documented need for a reusable, high-performing face mask for use by the public as a barrier to respiratory hazards.

Objective: This utility validation study sought to assess the functionality of a tubular-shaped, textile-based solution to enable the simple manufacture of a reusable face mask designed to minimize leakage and to achieve high levels of community protection from respiratory hazards.

Methods: We used a mechanistic approach to design, develop, and combine engineered components into an integrated tubular solution.  To ensure the desired features were optimized when integrated, after reprocessing we tested the entire mask, as worn, for physiological impact, comfort, filtration efficiency, and leakage. For several features, the novel design and tubular shape required in-house design and manufacture of new test equipment.  We tested fabrics, prototypes, and reprocessing protocols in-house and with academic partners.  Independent testing for certain features was available (e.g., EN14683 Medical Face Masks, ASTM F3502-21, Standard Specification for Barrier Face Coverings) and was used to confirm performance. 

Results: The tubular shape, special seals, unique harness, and three-layers of fabrics with distinct functions and composition work together to minimize leaks and ensure durability after repeated laundering. In-house testing indicated that designing a textile-based, tubular-shaped face mask optimized for source control with minimized leakage also resulted in wearer protection properties, even after hundreds of laundering cycles. Independent testing of one filter choice (Filter B) after 50 laundering cycles confirmed low breathing resistance (4.9 mm H₂O/48 Pa) and high filtration efficiency (96%) to ASTM F3502-21.

Conclusion: This utility validation study concludes that a reusable, tubular-shaped, textile-based face mask is capable of a universal fit as well as filtration efficiency and breathability performance levels that are similar to those for a disposable filtering facepiece respirator.

Keywords: Reusable mask, Filtration, Universal fit, Leakage, Breathability, Barrier face covering, Source control, Filtering facepiece respirator, Gaiter, Tubular face mask.