American Journal of Infection Control

BackgroundIsolation space must be expanded during pandemics involving airborne transmission. Little to no work has been done to establish optimal design strategies and implementation plans to ease surge capacity and expand isolation capacity over long periods in congregate living facilities. The COVID-19 pandemic has an airborne transmission component and requires isolation, which is difficult to accomplish in skilled nursing facilities. PurposeIn this study we designed, implemented, and validated an isolation space at a skilled nursing facility in Lancaster, PA. The overall goal was to minimize disease transmission between residents and staff within the facility. Basic ProceduresWe created an isolation space by modifying an existing HVAC system of the SNF. We measured pressure on-site and performed computational fluid dynamics and Lagrangian particle-based modeling to test containment and possible transmission extent given the isolation space is considered negative rather than individual rooms. Main FindingsPressure data shows the isolation space maintained an average hourly value of (standard deviation) -2.3 Pa (0.12 Pa) pressure differential between it and the external hallway connected to the rest of the facility. No transmission of SARS-CoV-2 between residents isolated to the space occurred, nor did any transmission to the staff or other residents occur. The isolation space was successfully implemented and, as of writing, continues to be operational through the pandemic. HighlightsO_LINegative pressure isolation space is an effective method to meet needed surge capacity during the COVID-19 pandemic and future pandemics C_LIO_LIPlanning for how and where to rapidly create a negative pressure isolation space is needed in congregate living areas such as skilled nursing facilities C_LIO_LIThis demonstration shows the feasibility of using low-cost and in-house systems to quickly create negative pressure within a skilled nursing facility hallway and to maintain these conditions, minimizing disease transmission between residents and staff C_LI

ImportanceThe outbreak of Coronavirus diseases 2019 (COVID-19) disease has increased demand for N95 respirators, surgical masks, and other facial coverings to stop the spread of SARS-CoV-2. Research shows that N95 respirators perform the best at filtering viral droplets and aerosols, however these masks are much more difficult to manufacture and expensive to distribute on a large scale, which led to shortages during the pandemic. Surgical masks, on the other hand, were more widely available and have been previously used to mitigate the spread of tuberculosis and influenza. ObjectivesTo evaluate the filter filtration efficiency (FFE) of three elastomeric harness designs in hospital and research settings in order to improve facemask seal. Design, setting and participantsA multi-institutional collaboration between engineers and health professionals, conducted between November 2020 and March 2021, was set up to design an elastomeric harness to improve the face seal of a surgical mask. Three elastomeric harness designs were created with harness designs 1 and 2 tested in a research laboratory setting and harness design 2.1 tested in a hospital setting. The initial harness design 1 was laser cut for testing and design 2 was developed to improve the detected particle leakage around the nose bridge area by introducing more material in that region. Design 2.1 is developed for hospital settings with less material around the nose bridge to reduce vision disruption. The designs were tested on mannequins and human volunteers using IR imaging and standard fit testing equipment. Main Outcomes and MeasuresOur elastomeric harness can improve the seal of a surgical mask allowing it to pass the fit test used to evaluate N95 respirators. 24/39 participants achieved a passing score of 100 or more while wearing the second harness design. IR imaging determined that the nasal sidewalls region of the mask is most prone to leakage when using our first elastomeric harness. Conclusions and RelevanceOverall, these results confirm that elastomeric harnesses combined with surgical masks improve their ability to filter aerosolized particles, which is especially important when in close proximity to individuals who are infectious or while performing aerosol-generating medical procedures.

Reprocessing of used N95 respirators may ameliorate supply chain constraints during the COVID-19 pandemic and provide a higher filtration crisis alternative. The FDA Medical Countermeasures Initiative previously funded a study of HP vapor decontamination of respirators using a Clarus C system (Bioquell, Horsham, PA) which normally is used to fumigate hospital rooms. The process preserved respirator function, but it is unknown if HP vapor would be virucidal since respirators have porous fabric that may harbor virus. We evaluated the virucidal activity of HP vapor using a BQ-50 system (Bioquell, Horsham, PA) after inoculating 3M 1870 N95 respirators (3M, St. Paul, MN) with 3 aerosolized bacteriophage that are a reasonable proxy for SARS-CoV-2. Inoculation resulted in contamination of the respirator with 9.87e4 plaque forming units (PFU) of phage phi-6, 4.17e7 PFU of phage T7 and 1.35e7 PFU of phage T1. Respirators were reprocessed with BQ-50 with a long aeration phase to reduce HP vapors. Virucidal activity was measured by a standard plaquing assay prior to and after sterilization. A single HP vapor cycle resulted in complete eradication of phage from masks (limit of detection 10 PFU, lower than the infectious dose of the majority of respiratory viral pathogens). After 5 cycles, the respirators appeared similar to new with no deformity. Use of a Bioquell machine can be scaled to permit simultaneous sterilization of a large number of used but otherwise intact respirators. HP vapor reprocessing may ease shortages and provide a higher filtration crisis alternative to non-NIOSH masks.

RationaleInhalation of ambient SARS-CoV-2-containing bioaerosols leads to infection and pandemic airborne transmission in susceptible populations. Filter-based respirators effectively reduce exposure but complicate normal respiration through breathing zone pressure differential and are therefore impractical for long-term use. ObjectivesWe tested the comparative effectiveness of a prototyped micronized electrostatic precipitator (mEP) to a filter-based respirator (N95) in the removal of viral bioaerosols from a simulated inspired air stream. MethodsEach respirator was tested within a 16-liter environmental chamber housed within a Class III biological safety cabinet within biosafety level 3 containment. SARS-CoV-2 containing bioaerosols were generated into the chamber, drawn by vacuum through each respirator, and physical particle removal and viral genomic RNA were measured distal to the breathing zone of each device. Measurement and Main ResultsThe mEP respirator removed particles (96.5{+/-}0.4%) approximating efficiencies of the N95 (96.9{+/-}0.6%). The mEP respirator similarly decreased SARS-CoV-2 viral RNA (99.792%) when compared to N95 removal (99.942%) as a function of particle removal from the airstream distal to the breathing zone of each respirator. ConclusionsThe mEP respirator approximated performance of a filter-based N95 respirator for particle removal and viral RNA as a constituent of the SARS-CoV-2 bioaerosols generated for this evaluation. In practice, the mEP respirator would provide equivalent protection from ambient infectious bioaerosols as the N95 respirator without undue pressure drop to the wearer, thereby facilitating long-term use in an unobstructed breathing configuration.

On May 12, 2023 CDC recommended 5 air changes per hour (5 ACH) and in July 2021 California (CDPH) recommended 6 to 12 ACH to reduce long-range, aerosol transmission of COVID-19 and other pathogens in classrooms. EPA recommends MERV 13+ DIY air cleaners for temporary use during wildfires, and a recent EPA study reported inconsistent usage in homes due to excessive noise generated by the DIY air cleaners. Questions also remain about wear and tear including how long filters retain their filtration properties and need to be replaced. Herein we report real-world experience from daily usage of 47 HEPA and 60 MERV 16 DIY air cleaners in a California elementary school during two academic school years from spring 2021 through fall of 2023 across 16 classrooms, a library, an auditorium, a lunchroom, and in a hallway. Three to six purifiers were needed in classrooms to meet 6 to 12 ACH. Teachers reported noise generated by MERV 16 DIY purifiers on lowest fan speed as acceptable for classroom use. Filtration efficiency at 0.3 m (most penetrating particle size) for DIY air cleaners with 5" MERV 16 filters used in the classrooms averaged 77% after six months (1st batch in February 2022) compared to 92% for newly installed filters (2nd batch in October 2022). Follow up testing on both batches of filters after an additional academic year (June 2023) showed only slight changes in average filtration efficiency. Portable air cleaners (HEPA and DIY) averaged and estimated 10 ACH (6-15 ACH) across the 16 classrooms demonstrating feasibility and unit economics of meeting CDPH targets per classroom for $200-$650 with DIY versus $600-$12,000 with the HEPA models used. In one 9000 cubic foot classroom with 7 air purifiers, air exchange rate was measured using ambient aerosols at 18 ACH from air purifiers (within 20% of ACH estimated based on CADR of purifiers) and 7 ACH from HVAC for a combined total of 25 ACH. Based on this long-term experience, specific recommendations for enhancing and improving CDCs web page "Ventilation in Buildings" include: (1) recommended operation of MERV 13+ DIY at their low speed for low noise, cost-effective air cleaning (2) electro-mechanical safety especially in relation to power outlets (3) an open-source procedure known as the "spike test" using ambient aerosols to verify ACH in a room, like the Portacount for mask fit testing. Spike testing can become the basis for ACH certification or verification in any room without generating aerosol contaminants (e.g. salt water, smoke, tracers which may be unsafe or disallowed indoors).

Coronavirus disease 2019 (COVID-19) is an illness caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease was first identified as a cluster of respiratory illness in Wuhan City, Hubei Province, China in December 2019, and has rapidly spread across the globe to greater than 200 countries. Healthcare providers are at an increased risk for contracting the disease due to occupational exposure and require appropriate personal protective equipment (PPE), including N95 respirators. The rapid worldwide spread of high numbers of COVID-19 cases has facilitated the need for a substantial supply of PPE that is largely unavailable in many settings, thereby creating critical shortages. Creative solutions for the decontamination and safe reuse of PPE to protect our frontline healthcare personnel are essential. Here, we describe the development of a process that began in late February 2020 for selecting and implementing the use of hydrogen peroxide vapor (HPV) as viable method to reprocess N95 respirators. Since pre-existing HPV decontamination chambers were not available, we optimized the sterilization process in an operating room after experiencing initial challenges in other environments. Details are provided about the prioritization and implementation of processes for collection and storage, pre-processing, HPV decontamination, and post-processing of filtering facepiece respirators (FFRs). Important lessons learned from this experience include, developing an adequate reserve of PPE for effective reprocessing and distribution, and identifying a suitable location with optimal environmental controls (i.e., operating room). Collectively, information presented here provides a framework for other institutions considering decontamination procedures for N95 respirators.

BACKGROUNDExhalation exposure from patients to healthcare workers (HCWs), while using a nasal cannula or simple O2 mask used in treating COVID-19 and other respiratory diseases, is a present and future risk. Little is known on exhalation dispersal through these devices, and on mitigating the viral exposure to those in the vicinity. METHODSRespiration through O2 therapy devices was studied with a supine manikin equipped with a controllable mechanical lung by measuring aerosol density and flow with direct imaging. Dispersal direction and distances were quantified while placing a surgical mask loosely over the devices and contrasted with unmitigated oxygenation device use. Exhalation jets were examined over the entire range of oxygenation rates used in treatment. RESULTSExhalation jets travel 0.35 {+/-} 0.02 m upward while wearing a nasal cannula, and 0.29 {+/-} 0.02 m laterally while wearing a simple O2 mask posing significant inhalation risk. Placing a surgical facemask loosely over the oxygenation device is demonstrated to alleviate exposure by reducing and deflecting the exhalation jets from being launched forward, and by reducing exhalations from being launched directly higher over a supine patient. Less than 12% of the exhaled breath is observed to reach above a masked face where HCWs would be present, independent of oxygen flow rates. CONCLUSIONSExhalation jets from both the nasal cannula or simple O2 mask were found to concentrate aerosol-laden exhalations directly in front of a patients face. Exposure is effectively mitigated with a surgical mask which reduces and redirects the exhalation downward away from HCWs.

ImportanceFiltering facepiece respirators, including N95 masks, are a critical component of infection prevention in hospitals. Due to unprecedented shortages in N95 respirators, many healthcare systems have explored reprocessing of N95 respirators. Data supporting these approaches are lacking in real hospital settings. In particular, published studies have not yet reported an evaluation of multiple viruses, bacteria, and fungi along with respirator filtration and fit in a single, full-scale study. ObjectiveWe initiated a full-scale study to evaluate different N95 FFR decontamination strategies and their impact on respirator integrity and inactivating multiple microorganisms, with experimental conditions informed by the needs and constraints of the hospital. MethodsWe explored several reprocessing methods using new 3M 1860 N95 respirators, including dry (<10% relative humidity) and moist (62-66% relative humidity) heat (80-82 {degrees}C) in the drying cycle of industrial instrument washers, ethylene oxide (EtO), pulsed xenon UV (UV-PX), hydrogen peroxide gas plasma (HPGP), and vaporous hydrogen peroxide (VHP). Respirator samples were treated and analyzed for biological indicator inactivation using four viruses (MS2, phi6, influenza A virus, murine hepatitis virus), three bacteria (Escherichia coli, Staphylococcus aureus, Geobacillus stearothermophilus), and the fungus Aspergillus niger. The impact of different application media was also evaluated. In parallel, decontaminated respirators were evaluated for filtration integrity and fit. ResultsVHP resulted in >2 log10 inactivation of all tested biological indicators. The combination of UV-PX + moist heat resulted in >2 log10 inactivation of all biological indicators except G. stearothermohphilus. Greater than 95% filtration efficiency was maintained following 2 (UV-PX + <10% relative humidity heat) or 10 (VHP) cycles of treatment, and proper fit was also preserved. UV-PX + dry heat was insufficient to inactivate all biological indicators. Although very effective at virus decontamination, HPGP resulted in decreased filtration efficiency after 3 cycles, and EtO treatment raised potential toxicity concerns. The observed inactivation of viruses with UV-PX, heat, and hydrogen peroxide treatments varied as a function of which culture media (PBS buffer or DMEM) they were deposited in. Conclusions and RelevanceHigh levels of biological indicator inactivation were achieved following treatment with either moist heat or VHP. These same treatments did not significantly impact mask filtration or fit. Hospitals have a variety of scalable options to safely reprocess N95 masks. Beyond value in the current Covid-19 pandemic, the broad group of microorganisms and conditions tested make these results relevant in potential future pandemic scenarios.

ObjectivesThe aim of this observational study was to demonstrate the behaviour and trajectory of exhaled material from an individual wearing an FFP3 mask. Valves allow material release, but we theorised that valve design may direct material downwards towards patient and surrounding environment. Limiting transmission of diseases with aerosolised spread is a current and serious concern within healthcare worldwide. Filtering face piece masks (FFP) are an essential piece of protective equipment when treating patients with ongoing infection. However, valved masks in other settings such as elective theatre and by the general public may have unforeseen negative effects. DesignA heating coil-based vaporiser was used to produce visible water vapour. A healthy test subject was filmed wearing a variety of different masks and exhaling the water vapour. ResultsFlexible pleated and solid-shell FFP masks direct exhaled material downwards in plumes exceeding 25 cm. Duckbill-shaped masks appear to direct exhaled vapour laterally, with a smaller plume. The effect is influenced by mask design and type of valve. Fluid repellent surgical masks reduce material directed downwards, and when used in conjunction with an FFP3 mask, appear to reduce the size and density of the exhaled vapour plume. The use of a visor was ineffective in reducing plume expulsion. InterpretationA properly fit-tested FFP3-rated protective mask may only moderately limit expulsion of aerosolised particles from asymptomatic healthcare workers to patients, particularly in cases where procedures are being performed in close proximity to patients or in cases where mucosal surfaces are exposed. Further research in this area is needed.

BackgroundThe unprecedented demand and consequent global shortage of N95 respirators during the COVID-19 pandemic have left frontline workers vulnerable to infection. To potentially expand the supply, we validated a rapidly applicable low-cost decontamination protocol in compliance with regulatory standards to enable the safe reuse of personalized, disposable N95-respirators. MethodsFour common models of N95-respirators were disinfected for 60 minutes at 70{degrees}C either at 0% or 50% relative humidity (RH). Effective inactivation of SARS-CoV-2 and E. coli was evaluated in inoculated masks. The N95 filter integrity was examined with scanning electron microscopy. The protective function of disinfected N95 respirators was tested against US NIOSH standards for particle filtration efficiency, breathing resistance and respirator fit. ResultsA single heat treatment inactivated both SARS-CoV-2 (undetectable, detection limit: 100 TCID50/ml) and E. coli (0 colonies at 50%RH) in all four respirator models. Even N95-respirators that underwent ten decontamination cycles maintained their integrity and met US-governmental criteria for approval regarding fit, filtration efficiency and breathing resistance. Scanning electron microscopy demonstrated maintained N95 fiber diameter compared to baseline. InterpretationThermal disinfection enables large-scale, low cost decontamination of existing N95 respirators using commonly sourced equipment during the COVID-19 pandemic. This process could be used in hospitals and long term care facilities and also provides a feasible approach to expand the N95 supply in low- and middle-income regions.

IntroductionOne of the important measures to prevent spread of COVID-19 in community is use of face mask. Though the debate is going on regarding the airborne transmission of SARS-CoV-2 it makes reasonable point for universal use of face masks. A large variety of face masks are available in the market or people can make their own using household items. The efficacy of masks depends upon the type of cloth and number of layers of the cloth. Material and methodsWe have created an innovative mask with two layers of cotton and an impervious layer. The impervious layer made from polypropylene coated with polyurethane was applied on the outer side in the middle half of the mask in front of mouth and nose. The efficacy of this test mask was measured against N95FFR (reference standard), triple layer surgical masks and single layer cotton mask. A manikin was used wearing these masks/respirator and aerosols/droplets of diluted red coloured carbol fuchsin and fluorescent Auramine O were sprayed from distance of 1m and 2m. We also tested use of face shield. Both macroscopic and microscopic examination of the dissected masks and respirator was performed. ResultsThe N95FFR was able to block the aerosols/droplets by its front layer. One triple layer surgical mask showed microscopic presence of stain in its innermost layer while the other blocked it with middle layer. The single layer cotton mask was not able to protect as we observed stain on the face itself. The test mask blocked most of the stain on impervious layer and also on the front cotton layer on lateral sides, where impervious layer was absent. When fluorescent stain was used, ultraviolet examination demonstrated that the whole area covered by test mask was clean while the other non covered area was fluorescent. ConclusionWe believe that our innovation can be used in the community as well as in general areas of the hospital like, offices, labs, etc. and can be a better alternative to single use triple layer surgical masks. Further testing may be done by other organizations to rule out bias in our study.

BackgroundCOVID-19 has stretched the ability of many institutions to supply needed personal protective equipment, especially N95 respirators. N95 decontamination and reuse programs provide one potential solution to this problem. Unfortunately, a comprehensive evaluation of the effects of decontamination on the integrity of various N95 models using a quantitative fit test (QTFT) approach is lacking. Aims1) To investigate the effects of up to eight rounds of vaporized H2O2 (VHP) decontamination on the integrity of N95 respirators currently in use in a hospital setting. 2) To examine if N95 respirators worn by one user can adapt to the face shape of a second user with no compromise of integrity following VHP decontamination. MethodsThe PortaCount Pro+ Respirator Fit Tester Model 8038 was used to quantitatively define the integrity, measured by fit, of N95 respirators following decontamination with VHP. FindingsThere was an observable downward trend in the integrity of Halyard Fluidshield 46727 N95 respirators throughout eight cycles of decontamination with VHP. The integrity of 3M 1870 N95 respirators was significantly reduced after the respirator was worn, decontaminated with VHP, and then quantitatively fit tested on a second user. Furthermore, we uncovered inconsistencies between qualitative fit test and QTFT results that may have strong implications on the fit testing method used by institutions. ConclusionsOur data revealed variability in the integrity of different N95 models after VHP decontamination and exposed potential limitations of N95 decontamination and reuse programs.

COVID-19 has demonstrated the devastating consequences of the rapid spread of an airborne virus in residential aged care. We report the use of CO2-based ventilation assessment to empirically identify potential "super-spreader" zones within an aged care facility, and determine the efficacy of rapidly implemented, inexpensive, risk reduction measures.

During the Covid-19 pandemic, pristine and reprocessed N95 respirators are crucial equipment towards limiting nosocomial infections. The NIOSH test certifying the N95 rating, however, poorly simulates aerosols in healthcare settings, limiting our understanding of the exposure risk for healthcare workers wearing these masks, especially reprocessed ones. We used experimental conditions that simulated the sizes, densities and airflow properties of infectious aerosols in healthcare settings. We analyzed the penetration and leakage of aerosols through pristine and reprocessed N95 respirators. Seven reprocessing methods were investigated. Our findings suggest that pristine and properly reprocessed N95 respirators effectively limit exposure to infectious aerosols, but that care must be taken to avoid the elucidated degradation mechanisms and limit noncompliant wear.

Study ObjectiveThe COVID-19 pandemic has resulted in widespread shortages in personal protective equipment, including N95 respirators. While basic surgical facemasks are more commonly available, their efficacy is limited due primarily to their poor face seal. This pilot study examined the impact of a rubber band mask brace on a basic surgical mask, as determined by quantitative fit testing. MethodsSubjects wearing a basic surgical facemask and the rubber band mask brace underwent quantitative fit testing using machinery designed to certify N95 mask fit. Subjects were tested with the brace anchored behind their eyes, with a paperclip behind the head, and on the side knobs of their face shields. The primary outcome measure was whether the subject passed the quantitative fit test at or above the OSHA verified standard for N95 masks. ResultsSubjects (n=11) were 54.5% female, with a median height of 70 inches (IQR 68-74), weight of 170 lbs (IQR 145-215) and BMI of 24.6 (IQR 22.2-27.2), and encompassing 5 distinct N95 mask fit types. We found that 45%, 100% and 100% of subjects passed the quantitative fit test when the brace was anchored behind the ears, with a paperclip and on a face shield respectively. ConclusionOf the 11 subjects included in the analysis, across a range of body habitus and N95 mask fit types, all passed the quantitative fit test when the mask brace was anchored on either face shield or with a paperclip. This data suggests the brace would offer an improved margin of safety when worn with a basic surgical mask.

BackgroundUsing face masks is one of the possible prevention methods against respiratory pathogens. A number of studies and reviews have been performed regarding the use of medical grade masks like surgical masks, N95 respirators etc. However, the use of cloth masks has received little attention. ObjectivesThe purpose of this review is to analyze the available data regarding the use of cloth masks for the prevention of respiratory infections. We intended to use data from both clinical and non-clinical studies to arrive at our conclusion. MethodsWe used PubMed, Cochrane Library and Google Scholar as our source databases. Both clinical and non-clinical studies, which had data regarding the efficacy of cloth masks, were selected. Articles not containing analyzable data including opinion articles, review articles etc. were excluded. After screening the search results, ten studies could be included in our review. Data relevant to our objective was extracted from each study including clinical efficacy, compliance, filtration efficacy etc. Data from some studies were simplified for the purpose of comparison. Extracted data was summarized and categorized for detailed analysis. Qualitative synthesis of the data was performed. But the heterogeneity between the studies did not allow for a meta-analysis. DiscussionThe review was limited by a lack of sufficient clinical studies. Lack of standardization between studies was another limitation. Although cloth masks generally perform poorer than the medical grade masks, they may be better than no masks at all. Filtration efficacy varied greatly depending on the material used, with some materials showing a filtration efficacy above 90%. However, leakage could reduce efficacy of masks by about 50%. Standardization of cloth masks and appropriate use is essential for cloth masks to be effective. However, result of a randomized controlled trial suggest that they may be ineffective in the healthcare setting.

Decontaminating N95 respirators for reuse could mitigate shortages during the COVID-19 pandemic. We tested a portable UV-C light-emitting diode disinfection chamber and found that decontamination efficacy depends on mask model, material and location on the mask. This emphasizes the need for caution when interpreting efficacy data of UV-C decontamination methods.

Given the current shortage of respirator masks and the resulting lack of personal protective equipment for use by clinical staff, we examined bottom-up solutions that would allow hospitals to fabricate respirator masks that: (i) meet requirements in terms of filtering capacities, (ii) are easy to produce rapidly and locally, and (iii) can be constructed using materials commonly available in hospitals worldwide. We found that Halyard H300 material used for wrapping of surgical instruments and routinely available in hospitals, met these criteria. Specifically, three layers of material achieved a filter efficiency of 94%, 99%, and 100% for 0.3 m, 0.5 m, and 3.0 m particles, respectively; importantly, these values are close to the efficiency provided by FFP2 and N95 masks. After re-sterilization up to 5 times, the filters efficiency remains sufficiently high for use as an FFP1 respirator mask. Finally, using only one layer of the material satisfies the criteria for use as a surgical mask. This material can therefore be used to help protect hospital staff and other healthcare professionals who require access to suitable masks but lack commercially available solutions.

Personal protective equipment (PPE) including N95 respirators are critical for persons exposed to SARS-CoV-2. KN95 respirators and N95 decontamination protocols have been described as solutions to a lack of such PPE. However, there are a few materials science studies that characterize the charge distribution and physical changes accompanying disinfection treatments particularly heating. Here, we report the filtration efficiency, dipole charge density, and fiber integrity of pristine N95 and KN95 respirators before and after various decontamination methods. We found that the filter layer of N95 is 8-fold thicker than that of KN95, which explains its 10% higher filtration efficiency (97.03 %) versus KN95 (87.76 %) under pristines condition. After 60 minutes of 70 {degrees}C treatment, the filtration efficiency and dipole charge density of N95 became 97.16% and 12.48 C/m2, while those of KN95 were 83.64% and 1.48 C/m2; moreover, fit factor of N95 was 55 and that of KN95 was 2.7. In conclusion, the KN95 respirator is an inferior alternative of N95 respirator. In both systems, a loss of electrostatic charge does not directly correlate to a decrease in performance.

As the Coronavirus 2019 pandemic creates worldwide shortages of personal protective equipment, hospitals have increasingly turned to sterilization and re-use protocols, often without significant data supporting the specific methodologies. When using UV-C irradiation, previously shown to be effective for decontaminating hard surfaces, modeling shows the importance of accounting for the porosity and non-uniform curvature of the N95 masks in decontamination procedures. Data shows a standard incident dose of 1 J/cm2 delivered to both front and back surfaces is more than 500x higher than the known kill dose. However, modeling indicates this would undertreat 40% of the mask material due to the curvature, path-length attenuation and scatter. Multidirectional UV-C irradiation employing dose calibrated exposures can adjust for this loss and best decontaminate masks. Such protocols can be rapidly implemented in thousands of hospitals across the world equipped with UV-C irradiation lamps without the need for additional capital equipment purchases.