The importance of fit testing in decontamination of N95 respirators: A cautionary note

Recommendations for change in infection prevention programs and practice

Fifty years of evolution in infection prevention and control programs have involved significant accomplishments related to clinical practices, methodologies, and technology. However, regulatory mandates, and resource and research limitations, coupled with emerging infection threats such as the COVID-19 pandemic, present considerable challenges for infection preventionists. This article provides guidance and recommendations in 14 key areas. These interventions should be considered for implementation by United States health care facilities in the near future.

Thermoplasmonics Decontamination of Respirators Face Masks Using Silver Nanoparticles: A New Weapon in the Fight Against COVID-19 Pandemic

The current COVID-19 pandemic has resulted in an urgent need for methods to decontaminate respirators masks for reuse while keeping them intact and functional. The severe shortage of professional masks such as N95 and FFP2 has necessitated their reuse over long periods. A very promising method is the pasteurization of these masks by thermoplasmonic heat generated by plasmonics nanoparticles when they are irradiated by light. Under illumination at its plasmonic resonance, a metal nanoparticle features enhanced light absorption, turning it into an ideal nano-source of heat, remotely controllable using light. In this work, we propose a numerical study based on the finite element method (FEM) of the thermoplasmonic properties of silver nanoparticles (AgNPs) decorating polypropylene (PP) fibers which is a basic material for the manufacture of these masks. The surface plasmon resonance (SPR) of these nanostructures was investigated through the computation of the complex effective dielectric permittivity and the absorption cross section in the near UV-visible (NUV-Vis) range. First, the SPR characteristics of AgNPs for different morphologies are determined from the absorption spectra, including the SPR-peak position λmax and the electric field enhancement. Second, we determine the power absorbed by an individual AgNP of different morphologies. From this, we calculate the internal temperature increase of the particle at the plasmonic resonance. The last step is devoted to the determination of the temperature profile in the surrounding medium in order to better understand and design the plasmon-assisted heating processes at the nanometric scale.

Efficacy of facemasks in mitigating respiratory exposure to submicron aerosols

We designed a novel experimental set-up to pseudo-simultaneously measure size-segregated filtration efficiency (η_F), breathing resistance (η_P) and potential usage time (t_B) for 11 types of face protective equipment (FPE; four respirators; three medical; and four handmade) in the submicron range. As expected, the highest η_F was exhibited by respirators (97 ± 3%), followed by medical (81 ± 7%) and handmade (47 ± 13%). Similarly, the breathing resistance was highest for respirators, followed by medical and handmade FPE. Combined analysis of efficiency and breathing resistance highlighted trade-offs, i.e. respirators showing the best overall performance across these two indicators, followed by medical and handmade FPE. This hierarchy was also confirmed by quality factor, which is a performance indicator of filters. Detailed assessment of size-segregated aerosols, combined with the scanning electron microscope imaging, revealed material characteristics such as pore density, fiber thickness, filter material and number of layers influence their performance. η_F and η_P showed an inverse exponential decay with time. Using their cross-over point, in combination with acceptable breathability, allowed to estimate t_B as 3.2-9.5 h (respirators), 2.6-7.3 h (medical masks) and 4.0-8.8 h (handmade). While relatively longer t_B of handmade FPE indicate breathing comfort, they are far less efficient in filtering virus-laden submicron aerosols compared with respirators.

Reusing and/or reprocessing the N95 face respirator mask or equivalent: An integrative review

OBJECTIVE

to analyze the scientific evidence available on the different reprocessing methods and the necessary conditions for reuse of the N95 face respirator mask or equivalent.

METHOD

an integrative literature review. The PICO strategy was used to elaborate the question. The search was conducted in four databases: PubMed, SciVerse Scopus, WebofScience and EMBASE, considering any period of time.

RESULTS

a total of 32 studies were included from the 561 studies identified, and they were presented in two categories: "Conditions for reuse" and "Reprocessing the masks". Of the evaluated research studies, seven(21.8%) addressed the reuse of the N95 face respirator mask or equivalent and 25(78.1%) evaluated different reprocessing methods, namely: ultraviolet germicidal irradiation(14); hydrogen peroxide(8); vapor methods(14); using dry heat(5) and chemical methods(sodium hypochlorite[6], ethanol[4] and sodium chloride with sodium bicarbonate and dimethyldioxirane[1]). We emphasize that different methods were used in one same article.

CONCLUSION

no evidence was found to support safe reprocessing of face respirator masks. In addition, reuse is contraindicated due to the risk of self-contamination and inadequate sealing.

Impact of ultraviolet germicidal irradiation on new silicone half-piece elastometric respirator (VJR-NMU) performance, structural integrity and sterility during the COVID-19 pandemic

Since the innovation of our new half-piece elastometric respirator, this type of filtering facepiece respirator (FFR) has been used widely in Thailand. Decontamination methods including ultraviolet C (UVC) germicidal irradiation and 70% alcohol have been implemented to decontaminate these respirators. We then examined the inactivation potential of different decontamination processes on porcine epidemic diarrhea virus (PEDV) and numerous bacterial strains, most of which were skin-derived. To enable rigorous integrity of the masks after repeated decontamination processes, fit tests by the Bitrex test, tensile strength and elongation at break were also evaluated. Our results showed that UVC irradiation at a dose of 3 J/cm2 can eradicate bacteria after 60 min and viruses after 10 min. No fungi were found on the mask surface before decontamination. The good fit test results, tensile strength and elongation at break were still maintained after multiple cycles of decontamination. No evidence of physical degradation was found by gross visual inspection. Alcohol (70%) is also an easy and effective way to eradicate microorganisms on respirators. As the current pandemic is expected to continue for months to years, the need to supply adequate reserves of personnel protective equipment (PPE) and develop effective PPE reprocessing methods is crucial. Our studies demonstrated that the novel silicone mask can be safely reprocessed and decontaminated for many cycles by UVC irradiation, which will help ameliorate the shortage of important protective devices in the COVID-19 pandemic era.

Practical considerations for Ultraviolet-C radiation mediated decontamination of N95 respirator against SARS-CoV-2 virus

Decontaminating N95 respirators for reuse could mitigate shortages during the COVID-19 pandemic. Although the United States Center for Disease Control has identified Ultraviolet-C irradiation as one of the most promising methods for N95 decontamination, very few studies have evaluated the efficacy of Ultraviolet-C for SARS-CoV-2 inactivation. In addition, most decontamination studies are performed using mask coupons that do not recapitulate the complexity of whole masks. We sought to directly evaluate the efficacy of Ultraviolet-C mediated inactivation of SARS-CoV-2 on N95 respirators. To that end we created a portable UV-C light-emitting diode disinfection chamber and tested decontamination of SARS-CoV-2 at different sites on two models of N95 respirator. We found that decontamination efficacy depends on mask model, material and location of the contamination on the mask. Our results emphasize the need for caution when interpreting efficacy data of UV-C decontamination methods.

The value of photomedicine in a global health crisis: Utilizing ultraviolet C to decontaminate N95 respirators during the COVID-19 pandemic

One early problem during the height of the COVID‐19 global pandemic, caused by severe acute respiratory syndrome 2 (SARS‐CoV‐2), was the shortage of personal protective equipment donned by healthcare workers, particularly N95 respirators. Given the known virucidal, bactericidal, and fungicidal properties of ultraviolet irradiation, in particular ultraviolet C (UVC) radiation, our photomedicine and photobiology unit explored the role of ultraviolet germicidal irradiation (UVGI) using UVC in effectively decontaminating N95 respirators. The review highlights the important role of photobiology and photomedicine in this pandemic. Namely, the goals of this review were to highlight: UVGI as a method of respirator disinfection—specifically against SARS‐CoV‐2, adverse reactions to UVC and precautions to protect against exposure, other methods of decontamination of respirators, and the importance of respirator fit testing.

The 2019 global pandemic and plastic pollution prevention measures: Playing catch-up

The early 2000's encompassed a rising awareness by the scientific community, the general public and policy makers of the impending environmental catastrophe caused by the increasing prevalence of plastics in the environment. Soon thereafter, a slew of regulatory initiatives and policies and actions targeting plastic pollution were put forth by governments, international institutions, non-governmental organizations, companies and even by citizen groups. However, the 2020 COVID19 pandemic has disrupted this momentum, and, presently, many fear that plastic pollution will increase, not only due to the increased consumption of single-use plastic items, but also due to the ever growing need of personal protective equipment. Many plastic pollution reduction policies have been suspended, cancelled or postponed. Herein, some of these delayed policies and initiatives are overviewed and, based on publicly available data, the questions as to whether, at a global level, increased government action to address plastic pollution will continue, or will the pandemic change this paradigm, are tentatively answered, as well as whether the pandemic will affect plastic production, in particular, single-use plastics, and what the potential routes to overcome these tendencies may be. As such, the dynamics of the interaction between the restrictive measures adopted in the wake of this pandemic and plastic pollution are examined, as are the roles of different legislative and regulatory bodies, whether at the local, regional or international levels.

Current Understanding of Ultraviolet-C Decontamination of N95 Filtering Facepiece Respirators

Introduction: The COVID-19 pandemic has led to critical shortages of single-use N95 filtering facepiece respirators. The US Centers for Disease Control and Prevention has identified ultraviolet-C (UV-C) irradiation as one of the most promising decontamination methods during crisis-capacity surges; however, understanding the mechanism of pathogen inactivation and post-treatment respirator performance is central to effective UV-C decontamination. Objective: We summarize the UV-C N95 decontamination evidence and identify key metrics. Methods: We evaluate the peer-reviewed literature on UV-C decontamination to inactivate SARS-CoV-2, viral analogues, and other microorganisms inoculated on N95s, as well as the resulting effect on respirator fit and filtration. Where peer-reviewed studies are absent, we discuss outstanding questions and ongoing work. Key Findings: Evidence supports that UV-C exposure of ≥1.0 J/cm2 inactivates SARS-CoV-2 analogues (≥3-log reduction) on the majority of tested N95 models. The literature cautions that (1) viral inactivation is N95 model-dependent and impeded by shadowing, (2) N95 straps require secondary decontamination, (3) higher doses may be necessary to inactivate other pathogens (e.g., some bacterial spores), and (4) while N95 fit and filtration appear to be preserved for 10-20 cycles of 1.0 J/cm2, donning and doffing may degrade fit to unacceptable levels within fewer cycles. Results and Discussion: Effective N95 UV-C treatment for emergency reuse requires both (1) inactivation of the SARS-CoV-2 virus, achieved through application of UV-C irradiation at an appropriate wavelength and effective dose, and (2) maintenance of the fit and filtration efficiency of the N95. Conclusions: UV-C treatment is a risk-mitigation process that should be implemented only under crisis-capacity conditions and with proper engineering, industrial hygiene, and biosafety controls.

Filtering Facepiece Respirator (N95 Respirator) Reprocessing: A Systematic Review

IMPORTANCE

The COVID-19 pandemic has resulted in a persistent shortage of personal protective equipment; therefore, a need exists for hospitals to reprocess filtering facepiece respirators (FFRs), such as N95 respirators.

OBJECTIVE

To perform a systematic review to evaluate the evidence on effectiveness and feasibility of different processes used for decontaminating N95 respirators.

EVIDENCE REVIEW

A search of PubMed and EMBASE (through January 31, 2021) was completed for 5 types of respirator-decontaminating processes including UV irradiation, vaporized hydrogen peroxide, moist-heat incubation, microwave-generated steam, and ethylene oxide. Data were abstracted on process method, pathogen removal, mask filtration efficiency, facial fit, user safety, and processing capability.

FINDINGS

Forty-two studies were included that examined 65 total types of masks. All were laboratory studies (no clinical trials), and 2 evaluated respirator performance and fit with actual clinical use of N95 respirators. Twenty-seven evaluated UV germicidal irradiation, 19 vaporized hydrogen peroxide, 9 moist-heat incubation, 10 microwave-generated steam, and 7 ethylene oxide. Forty-three types of N95 respirators were treated with UV irradiation. Doses of 1 to 2 J/cm2 effectively sterilized most pathogens on N95 respirators (>103 reduction in influenza virus [4 studies], MS2 bacteriophage [3 studies], Bacillus spores [2 studies], Escherichia virus MS2 [1 study], vesicular stomatitis virus [1 study], and Middle East respiratory syndrome virus/SARS-CoV-1 [1 study]) without degrading respirator components. Doses higher than 1.5 to 2 J/cm2 may be needed based on 2 studies demonstrating greater than 103 reduction in SARS-CoV-2. Vaporized hydrogen peroxide eradicated the pathogen in all 7 efficacy studies (>104 reduction in SARS-CoV-2 [3 studies] and >106 reduction of Bacillus and Geobacillus stearothermophilus spores [4 studies]). Pressurized chamber systems with higher concentrations of hydrogen peroxide caused FFR damage (6 studies), while open-room systems did not degrade respirator components. Moist heat effectively reduced SARS-CoV-2 (2 studies), influenza virus by greater than 104 (2 studies), vesicular stomatitis virus (1 study), and Escherichia coli (1 study) and preserved filtration efficiency and facial fit for 11 N95 respirators using preheated containers/chambers at 60 °C to 85 °C (5 studies); however, diminished filtration performance was seen for the Caron incubator. Microwave-generated steam (1100-W to 1800-W devices; 40 seconds to 3 minutes) effectively reduced pathogens by greater than 103 (influenza virus [2 studies], MS2 bacteriophage [3 studies], and Staphylococcus aureus [1 study]) and maintained filtration performance in 10 N95 respirators; however, damage was noted in least 1 respirator type in 4 studies. In 6 studies, ethylene oxide preserved respirator components in 16 N95 respirator types but left residual carcinogenic by-product (1 study).

CONCLUSIONS AND RELEVANCE

Ultraviolet germicidal irradiation, vaporized hydrogen peroxide, moist heat, and microwave-generated steam processing effectively sterilized N95 respirators and retained filtration performance. Ultraviolet irradiation and vaporized hydrogen peroxide damaged respirators the least. More research is needed on decontamination effectiveness for SARS-CoV-2 because few studies specifically examined this pathogen.

Unlocking the surge in demand for personal and protective equipment (PPE) and improvised face coverings arising from coronavirus disease (COVID-19) pandemic - Implications for efficacy, re-use and sustainable waste management

Currently, there is no effective vaccine for tackling the ongoing COVID-19 pandemic caused by SARS-CoV-2 with the occurrence of repeat waves of infection frequently stretching hospital resources beyond capacity. Disease countermeasures rely upon preventing person-to-person transmission of SARS-CoV2 so as to protect front-line healthcare workers (HCWs). COVID-19 brings enormous challenges in terms of sustaining the supply chain for single-use-plastic personal and protective equipment (PPE). Post-COVID-19, the changes in medical practice will drive high demand for PPE. Important countermeasures for preventing COVID-19 transmission include mitigating potential high risk aerosol transmission in healthcare setting using medical PPE (such as filtering facepiece respirators (FFRs)) and the appropriate use of face coverings by the general public that carries a lower transmission risk. PPE reuse is a potential short term solution during COVID-19 pandemic where there is increased evidence for effective deployment of reprocessing methods such as vaporized hydrogen peroxide (30 to 35% VH2O2) used alone or combined with ozone, ultraviolet light at 254 nm (2000 mJ/cm2) and moist heat (60 °C at high humidity for 60 min). Barriers to PPE reuse include potentially trust and acceptance by HCWs. Efficacy of face coverings are influenced by the appropriate wearing to cover the nose and mouth, type of material used, number of layers, duration of wearing, and potentially superior use of ties over ear loops. Insertion of a nose clip into cloth coverings may help with maintaining fit. Use of 60 °C for 60 min (such as, use of domestic washing machine and spin dryer) has been advocated for face covering decontamination. Risk of virus infiltration in improvised face coverings is potentially increased by duration of wearing due to humidity, liquid diffusion and virus retention. Future sustained use of PPE will be influenced by the availability of recyclable PPE and by innovative biomedical waste management.

Decontamination of N95 respirators against SARS-CoV-2: A scoping review

OBJECTIVES

This scoping review aimed to map and compile the available evidence regarding the effectiveness of decontaminating N95 respirators against the novel coronavirus (SARS-CoV-2).

DATA

We selected studies written in English assessing or discussing the decontamination strategies of N95 respirators against SARS-CoV-2. Two independent researchers performed the search and study screening. A descriptive analysis was carried out considering the study design of the included studies.

SOURCES

PubMed, SCOPUS, and Preprint platforms (bioRxiv and medRxiv).

STUDY SELECTION

We included 55 reports from PubMed and SCOPUS. Nine articles were letters to the editors, 21 were in vitro studies, 16 were literature reviews, and 9 were classified as other study designs. We included 37 preprints. Two articles were letters to the editors, 24 were in vitro studies, 3 were literature reviews, and 8 were classified as other study designs. In general, vaporized hydrogen peroxide and ultraviolet irradiation were the strategies most cited and most promising. However, there is a lack of evidence and consensus related to the best method of N95 respirator decontamination.

CONCLUSION

The evidence regarding decontamination strategies of N95 respirators against SARS-CoV-2 remains scarce. Vaporized hydrogen peroxide and ultraviolet irradiation seem to be the current standard for N95 respirator decontamination.

CLINICAL SIGNIFICANCE

Vaporized hydrogen peroxide and ultraviolet irradiation appear to be the most promising methods for N95 respirator decontamination.

The effect of ultraviolet C radiation against different N95 respirators inoculated with SARS-CoV-2

OBJECTIVES

There are currently no studies that have examined whether one dosage can be uniformly applied to different respirator types to effectively decontaminate SARS-CoV-2 on N95 filtering facepiece respirators (FFRs). Health care workers have been using this disinfection method during the pandemic. Our objective was to determine the effect of UVC on SARS-CoV-2 inoculated N95 respirators and whether this was respirator material/model type dependent.

METHODS

Four different locations (facepiece and strap) on five different N95 FFR models (3M 1860, 8210, 8511, 9211; Moldex 1511) were inoculated with a 10 μL drop of SARS-CoV-2 viral stock (8 × 10⁷ TCID₅₀/mL). The outside-facing and wearer-facing surfaces of the respirators were each irradiated with a dose of 1.5 J/cm² UVC (254 nm). Viable SARS-CoV-2 was quantified by a median tissue culture infectious dose assay (TCID₅₀).

RESULTS

UVC delivered using a dose of 1.5 J/cm², to each side, was an effective method of decontamination for the facepieces of 3M 1860 and Moldex 1511, and for the straps of 3M 8210 and the Moldex 1511.

CONCLUSION

This dose is an appropriate decontamination method to facilitate the reuse of respirators for healthcare personnel when applied to specific models/materials. Also, some straps may require additional disinfection to maximize the safety of frontline workers. Implementation of widespread UVC decontamination methods requires careful consideration of model, material type, design, and fit-testing following irradiation.

Rapid Review of SARS-CoV-1 and SARS-CoV-2 Viability, Susceptibility to Treatment, and the Disinfection and Reuse of PPE, Particularly Filtering Facepiece Respirators

In the COVID-19 pandemic caused by SARS-CoV-2, hospitals are often stretched beyond capacity. There are widespread reports of dwindling supplies of personal protective equipment (PPE), particularly N95-type filtering facepiece respirators (FFRs), which are paramount to protect frontline medical/nursing staff, and to minimize further spread of the virus. We carried out a rapid review to summarize the existing literature on the viability of SARS-CoV-2, the efficacy of key potential disinfection procedures against the virus (specifically ultraviolet light and heat), and the impact of these procedures on FFR performance, material integrity, and/or fit. In light of the recent discovery of SARS-CoV-2 and limited associated research, our review also focused on the closely related SARS-CoV-1. We propose a possible whole-of-PPE disinfection solution for potential reuse that could be rapidly instituted in many health care settings, without significant investments in equipment.

Spectrum of virucidal activity from ultraviolet to infrared radiation

The COVID-19 pandemic has sparked a demand for safe and highly effective decontamination techniques for both personal protective equipment (PPE) and hospital and operating rooms. The gradual lifting of lockdown restrictions warrants the expansion of these measures into the outpatient arena. Ultraviolet C (UVC) radiation has well-known germicidal properties and is among the most frequently reported decontamination techniques used today. However, there is evidence that wavelengths beyond the traditional 254 nm UVC - namely far UVC (222 nm), ultraviolet B, ultraviolet A, visible light, and infrared radiation - have germicidal properties as well. This review will cover current literature regarding the germicidal effects of wavelengths ranging from UVC through the infrared waveband with an emphasis on their activity against viruses, and their potential applicability in the healthcare setting for general decontamination during an infectious outbreak.