Infection Control & Hospital Epidemiology

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.

IntroductionTransmission of SARS-Cov-2 through aerosol has been implicated particularly in the presence of highly concentrated aerosols in enclosed environments. It is accepted that aerosols are produced during a range of dental procedures, posing potential risks to both dental practitioners and patients. There has been little agreement concerning aerosol transmission associated with orthodontics and associated mitigation. MethodsOrthodontic procedures were simulated in a closed side-surgery using a dental manikin on an acrylic model using composite-based adhesive. Adhesive removal representing debonding was undertaken using a 1:1 contra-angle handpiece (W&H Synea Vision WK-56 LT, Burmoos, Austria) and fast hand-piece with variation in air and water flow. The removal of acid etch was also simulated with use of combined 3-in-1 air water syringe to remove etch. An Optical Particle Sizer (OPS 3330, TSI Inc. Minnesota, USA) and a portable Scanning Mobility Particle Sizer (NanoScan SMPS Nanoparticle Sizer 3910, TSI Inc Minnesota, USA) were both to assess particulate matter ranging from very small (0.08 - 0.26 m) to large (2.7 - 10 m) particles. ResultsStandard debonding procedure (involving air but no water) was associated with clear increase in the very small and small (0.26 - 0.9 m) particles but only for a short period. Debonding procedures without air appeared to produce similar levels of aerosol to standard debonding. Debonding in association with water tended to produce large increase in aerosol levels, producing particles of all sizes throughout the experiment. The use of water and a fast hand-piece led to the most significant increase in particles. Combined use of the 3-in-1 air water syringe did not result in any detectable increase in the aerosol levels. ConclusionsParticulate matter was released during orthodontic debonding, although the concentration and volume was markedly less than that associated with the use of a fast hand-piece. No increase in particulates was associated with prolonged use of a 3-in-1 air-water syringe. Particulate levels reduced to baseline levels over a short period (approx. 5 minutes). Further research within alternative, open environments and without air exchange systems is required.

Dental procedures produce aerosols which may remain suspended and travel significant distances from the source. Dental aerosols and droplets contain oral microbes and there is potential for infectious disease transmission and major disruption to dental services during infectious disease outbreaks. One method to control hazardous aerosols often used in industry is Local Exhaust Ventilation (LEV). The aim of this study was to investigate the effect of LEV on aerosols and droplets produced during dental procedures. Experiments were conducted on dental mannequins in an 825.4 m3 open plan clinic, and a 49.3 m3 single surgery. 10-minute crown preparations were performed with an air-turbine handpiece in the open plan clinic, and 10-minute full mouth ultrasonic scaling in the single surgery. Fluorescein was added to instrument irrigation reservoirs as a tracer. In both settings, Optical Particle Counters (OPCs) were used to measure aerosol particles between 0.3 - 10.0 m and liquid cyclone air samplers were used to capture aerosolised fluorescein tracer. Additionally, in the open plan setting fluorescein tracer was captured by passive settling onto filter papers in the environment. Tracer was quantified fluorometrically. An LEV device with High Efficiency Particulate Air (HEPA) filtration and a flow rate of 5,000 L/min was used. LEV reduced aerosol production from the air-turbine handpiece by 90% within 0.5 m, and this was 99% for the ultrasonic scaler. OPC particle counts were substantially reduced for both procedures, and air-turbine settled droplet detection reduced by 95% within 0.5 m. The effect of LEV was substantially greater than suction alone for the air-turbine and was similar to the effect of suction for the ultrasonic scaler. LEV reduces aerosol and droplet contamination from dental procedures by at least 90% in the breathing zone of the operator and it is therefore a valuable tool to reduce the dispersion of dental aerosols.

A systematic review was performed to answer the following questions: 1) Do dental, oral and maxillofacial (OMF) surgical procedures generate bioaerosols (and if so, which ones), which can result in transmission of COVID-19?; 2) Are aerosolized airborne droplets (and to which extent is splatter) in dental and OMF procedures infective?; 3) Is enhanced personal protective equipment (PPE) an essential to prevent spreading of COVID-19 during dental and OMF aerosol generating procedures (AGPs)? Authors performed a systematic review to retrieve all pertinent literature that assessed effectiveness of surgical mask vs respirators for protecting dental health care workers during dental and OMF AGPs surgical procedures. Additionally, studies which assessed potential aerosolization during dental, OMF and orthopaedic surgeries were retrieved. There is moderate evidence showing that ultrasonic scaling and bone drilling using high speed rotary instruments produces respirable aerosols. Additionally, there is very weak/inconclusive evidence to support the creation of infectious aerosols during dental procedures. According to available very weak/inconclusive evidence, transmission of SARS-CoV-2 via infective aerosol during AGPS, so far, must remain speculative and controversial. As, however, this is a probable opportunistic way of transmission which at least cannot be sufficiently excluded and therefore should not be dismissed out of hand prematurely, proper and equally important properly applied protective equipment (i.e., N95 respirators or FFP-2 masksv or above regarding mouth and nose protection) should always be used during AGPs.

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.

Decontamination of N95 respirators has become critical to alleviate PPE shortages for healthcare workers in the current COVID-19 emergency. The factors that are considered for the effective reuse of these masks are the fit, filter efficiency and decontamination/disinfection level both for SARS-CoV2, which is the causative virus for COVID-19, and for other organisms of concern in the hospital environment such as Staphylococcus aureus or Clostridium difficile. The efficacy of inactivation or eradication against various pathogens should be evaluated thoroughly to understand the level of afforded disinfection. Methods commonly used in the sterilization of medical devices such as ionizing radiation, vaporized hydrogen peroxide, and ethylene oxide can provide a high level of disinfection, defined as a 6 log10 reduction, against bacterial spores, considered the most resistant microorganisms. CDC guidance on the decontamination and reuse of N95s also includes the use of moist heat (60{degrees}C, 80% relative humidity, 15-30 min) as a possible recommendation based on literature showing preservation of fit efficiency and inactivation of H1N1 on spiked masks. Here, we explored the efficacy of using moist heat under these conditions as a decontamination method for an N95 respirator (3M 1860S, St. Paul, MN) against various pathogens with different resistance; enveloped RNA viruses, Gram (+/-) bacteria, and non-enveloped viruses.

The study was undertaken to record the amount of dental aerosol created using 3-in-1 syringe, air rotor, and ultrasonic scaler using high volume suction (HVS) in 5 primary care dental surgeries. The time for the aerosol to dissipate following completion of the procedure was also recorded. The amount of aerosol created above the background level for the surgery corresponding to the operating positions of the nurse, dentist, and patient was recorded using particle meters measuring the number of 2.5{micro}m (PM2.5) and 10{micro}m (PM10) particles respectively. The procedures were recorded in triplicate for each surgery and average change calculated for each procedure, lasting 90 seconds. PM2.5 remained at or very near background readings during all procedures, whereas PM10 increased with use of the air rotor and to a much lower extent with both 3-in-1, and ultrasonic scaler. The means time to return to background reading level was 2.5 minutes. It was concluded that PM2.5 levels did not rise and although PM10 increased for all procedures the increase was low and with a return to background readings within 2m:50s (95% CI: 2:34 to 3:37) of completing the procedures that a minimum fallow period of 5minutes would allow be more than ample to be safe.

ObjectiveThe COVID-19 pandemic has led to widespread shortages of personal protective equipment (PPE) for healthcare workers, including filtering facepiece respirators (FFRs) such as N95 masks. These masks are normally intended for single use, but their sterilization and subsequent reuse could substantially mitigate a world-wide shortage. DesignQuality assurance. SettingA sealed environment chamber installed in the animal facility of an academic medical center. InterventionsOne to five sterilization cycles using ionized hydrogen peroxide (iHP), generated by SteraMist(R) equipment (TOMI; Frederick, MD). Main outcome measuresPersonal protective equipment, including five N95 mask models from three manufacturers, were evaluated for efficacy of sterilization following iHP treatment (measured with bacterial spores in standard biological indicator assemblies). Additionally, N95 masks were assessed for their ability to efficiently filter particles down to 0.3{micro}m and for their ability to form an airtight seal using a quantitative fit test. Filtration efficiency was measured using ambient particulate matter at a university lab and an aerosolized NaCl challenge at a National Institute for Occupational Safety and Health (NIOSH) pre-certification laboratory. ResultsThe data demonstrate that N95 masks sterilized using SteraMist iHP technology retain function up to five cycles, the maximum number tested to date. Some but not all PPE could also be sterilized using an iHP environmental chamber, but pre-treatment with a handheld iHP generator was required for semi-enclosed surfaces such as respirator hoses. ConclusionsA typical iHP environment chamber with a volume of ~80 m3 can treat ~7000 masks per day, as well as other items of PPE, making this an effective approach for a busy medical center.

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.

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.

Decontamination of N95 respirators has become critical to alleviate PPE shortages for healthcare workers in the current COVID-19 emergency. The factors that are considered for the effective reuse of these masks are the fit, filter efficiency and decontamination/disinfection level both for SARS-CoV-2, which is the causative virus for COVID-19, and for other organisms of concern in the hospital environment such as Staphylococcus aureus or Clostridium difficile. In its guidance entitled Recommendations for Sponsors Requesting EUAs for Decontamination and Bioburden Reduction Systems for Surgical Masks and Respirators During the Coronavirus Disease 2019 (COVID19) Public Health Emergency (May 2020)[1], the FDA recommends a 6-log10 reduction in either the most resistant bacterial spores for the system or in a mycobacterium species to authorize the use of a decontamination method of N95 respirators for single or multiple users. While the goal is primarily inactivation against SARS-CoV-2, testing of decontamination methods against the virus may not always be available. For decontamination methods considered for only single users, the recommendation is a 6-log10 reduction in the infective virus concentration of 3 non-enveloped viruses or in the concentration of two Gram (+) and two Gram (-) bacteria. Based on these recommendations, we explored the efficacy of vaporized H2O2 (VHP) treatment of N95 respirators against surrogate viruses covering a wide range of disinfection resistance for emergency decontamination and reuse to alleviate PPE shortages for healthcare workers in the COVID-19 emergency.

ObjectivesAgainst the COVID-19 pandemic backdrop and potential disease transmission risk by dental procedures that can generate aerosol and droplets, this review aimed to identify which clinical dental procedures do generate droplets and aerosols with subsequent contamination, and for these, characterise their pattern, spread and settle. Data SourcesSix databases were searched and citation chasing undertaken (to 11/08/20). Study selectionScreening stages were undertaken in duplicate, independently, by two researchers. Data extraction was performed by one reviewer and verified by another. ResultsEighty-three studies met the inclusion criteria and covered: Ultrasonic scaling (USS, n=44), highspeed air-rotor (HSAR, n=31); oral surgery (n=11), slow-speed handpiece (n=4); air-water (triple) syringe (n=4), air-polishing (n=4), prophylaxis (n=2) and hand-scaling (n=2). Although no studies investigated respiratory viruses, those on bacteria, blood splatter and aerosol showed activities using powered devices produced the greatest contamination. Contamination was found for all activities, and at the furthest points studied. The operators torso operators arm, and patients body were especially affected. Heterogeneity precluded significant inter-study comparisons but intra-study comparisons allowed construction of a proposed hierarchy of procedure contamination risk: higher risk (USS, HSAR, air-water syringe [air only or air/water together], air polishing, extractions using motorised handpieces); moderate (slow-speed handpieces, prophylaxis with pumice, extractions) and lower (air-water syringe [water only] and hand scaling. ConclusionSignificant gaps in the evidence, low sensitivity of measures and variable quality limit firm conclusions around contamination for different procedures. However, a hierarchy of contamination from procedures can be proposed for challenge/verification by future research which should consider standardised methodologies to facilitate research synthesis. Clinical significanceThis manuscript addresses uncertainty around aerosol generating procedures (AGPs) in dentistry. Findings indicate a continuum of procedure-related aerosol generation rather than the current binary AGP or non-AGP perspective. This informs discussion around AGPs and direct future research to help support knowledge and decision making around COVID-19 and dental procedures.

ObjectivesThis study was undertaken to assess the amount of dental aerosol created in a primary care dental surgery. MethodsTwo particle meters were placed a set distances round a volunteer patient whilst undergoing simulated dental treatment using a high speed dental handpiece, and 3-in-1 air/water syringe, moisture control was managed with high volume suction and a saliva ejector. Measurement were taken every thirty seconds with the surgery environment set a neutral ventilation and with the windows open plus fan assistance. ResultsFrom the cessation of aerosol generation it took between 6 and 19 minutes for the surgery to return to baseline. The ventilated surgery had faster aerosol dispersal, returning to background levels within 5 minutes. ConclusionIt is concluded for the surgery under investigation the dental aerosol had dissipated after 30 minutes using HVS and optimal surgery.

BackgroundCritical shortages of personal protective equipment (PPE) especially N95 respirators, during the SARS-CoV-2 pandemic continues to be a source of great concern among health care workers (HCWs). Novel methods of N95 filtering facepiece respirator (FFR) decontamination that can be scaled-up for in-hospital use can help address this concern and keep HCWs safe. MethodsA multidisciplinary pragmatic study was conducted to evaluate the use of an ultrasonic room high-level disinfection system (HLDS) that generates aerosolized peracetic acid (PAA) and hydrogen peroxide for decontamination of large numbers of N95 respirators. A cycle duration that consistently achieved disinfection of N95 respirators (defined as [&le;] 6 log10 reductions in bacteriophage MS2 and Geobacillus stearothermophilus spores inoculated onto respirators) was identified. The treated masks were then assessed for changes to their hydrophobicity, material structure, strap elasticity, and filtration efficiency (FE). Assessment of PAA off-gassing from a treated mask was also performed. ResultsThe PAA room HLDS was effective for disinfection of N95 respirators in a 2447 cubic feet room with deploy and dwell times of 16 and 32 minutes respectively, and a total cycle time of 1 hour and 16 minutes. After 5 treatment cycles, no adverse effects were detected on filtration efficiency, structural integrity, or strap elasticity. There was no detectable off-gassing of PAA from the treated masks. ConclusionThe PAA room disinfection system provides a rapidly scalable solution for in-hospital decontamination of large numbers of N95 respirators to meet the needs of HCWs during the SARS-CoV-2 pandemic.

We conducted a systematic review of hygiene intervention effectiveness against SARS-CoV-2, including developing inclusion criteria, conducting the search, selecting articles for inclusion, and summarizing included articles. We reviewed 104,735 articles, and 109 articles meeting inclusion criteria were identified, with 33 additional articles identified from reference chaining. Herein, we describe results from 58 mask disinfection and reuse studies, where the majority of data were collected using N95 masks. Please note, no disinfection method consistently removed >3 log of virus irrespective of concentration, contact time, temperature, and humidity. However, results show it is possible to achieve >3 log reduction of SARS-CoV-2 using appropriate concentrations and contact times of chemical (ethanol, hydrogen peroxide, peracetic acid), radiation (PX-UV, UVGI), and thermal (autoclaving, heat) disinfection on N95 masks. N95 mask reuse and failure data indicate that hydrogen peroxide, heat, and UV-GI are promising for mask reuse, peracetic acid and PX-UV need more data, and autoclaving and ethanol lead to mask durability failures. Data on other mask types is limited. We thus recommend focusing guidelines and further research on the use of heat, hydrogen peroxide, and UVGI for N95 mask disinfection/reuse. All of these disinfection options could be investigated for use in LMIC and humanitarian contexts. TOC Art O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/20229880v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@154383borg.highwire.dtl.DTLVardef@37b888org.highwire.dtl.DTLVardef@33eae1org.highwire.dtl.DTLVardef@818e32_HPS_FORMAT_FIGEXP M_FIG C_FIG SynopsisIn resource-limited contexts, N95s are reused. We recommend using heat, hydrogen peroxide, or UVGI to disinfect and reuse N95 masks.

The coronavirus disease 2019 crisis is creating a shortage of personal protective equipment (PPE), most critically, N95 respirators for healthcare personnel. Our group was interested in the feasibility of ozone disinfection of N95 respirators as an alternative for healthcare professionals and organizations that might not have access to other disinfection devices. We tested the effectiveness of ozone on killing Pseudomonas aeruginosa (PsA) on three different N95 respirators: 3M 1860, 3M 1870, and 3M 8000. We used an ozone chamber that consisted of: an airtight chamber, an ozone generator, an ozone destruct unit, and an ozone UV analyzer. The chamber was capable of concentrating ozone up to 500 parts per million (ppm) from ambient air, creating an airtight seal, and precisely measuring ozone levels within the chamber. Exposure to ozone at 400 ppm with 80% humidity for two hours effectively killed bacteria on N95 respirators, types 1860, 1870, and 8000. There were no significant changes in filtration efficiency of the 1860 and 1870 type respirators for up to ten cycles of ozone exposure at similar conditions. There was no change in fit observed in the 1870 type respirator after ozone exposure. There was no significant change in the strap integrity of the 1870 type respirator after ozone exposure. Tests for filtration efficiency were not performed on the 8000 type respirator. Tests for fit or strap integrity were not performed on the 8000 or 1860 type respirators. This study demonstrates that an ozone application achieves a high level of disinfection against PsA, a vegetative bacteria that the CDC identifies as more difficult to kill than medium sized viruses such as SARS-CoV-2 (Covid-19). Furthermore, conditions shown to kill these bacteria did not damage or degrade respirator filtration. This is the first report of successful disinfection of N95 PPE with ozone of which the authors are aware. It is also the first report, to the authors knowledge, to identify necessary conditions for ozone to kill organisms on N95 masks without degrading the function of N95 filters.

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.

ObjectiveThere are widespread shortages of personal protective equipment as a result of the coronavirus disease 2019 (COVID-19) pandemic. Reprocessing filtering facepiece respirators may provide an alternative solution in keeping health care professionals safe. Designprospective, bench-to-bedside SettingA primary care-based study using filtering facepiece particles (FFP) type 2 respirators without exhalation valve (3M Aura 1862+, Maco Pharma ZZM002), FFP2 respirators with valve (3M Aura 9322+ and San Huei 2920V), and valved FFP type 3 respirators (Safe Worker 1016). InterventionsAll masks were reprocessed using a medical autoclave (34-minute total cycle time of steam sterilization, with 17 minutes at 121{degrees}C) and subsequently tested up to 3 times whether these decontaminated respirators retained their integrity (seal check, pressure drop) and ability to filter small particles (0.3-5.0m) in the laboratory using a particle penetration test. ResultsWe tested 32 respirators, and 63 samples for filter capacity. All 27 FFP-2 respirators retained their shape, whereas half of the sterilized FFP-3 respirators (Safe Worker 1116) showed deformities and failed the seal check. The filtering capacity of the 3M Aura 1862 was best retained after 1, 2, and 3 sterilization cycles (0.3m: 99.3{+/-}0.3% (new) versus 97.0{+/-}1.3, 94.2{+/-}1.3% or 94.4{+/-}1.6, p<0.001). Of the other FFP-2 respirators, the San Huei 2920V had 95.5{+/-}0.7% at baseline versus 92.3{+/-}1.7% versus 90.0{+/-}0.7 after one- and two-time sterilization, respectively (p<0.001). The tested FFP-3 respirator (Safe Worker 1016) had a filter capacity of 96.5{+/-}0.7% at baseline and 60.3{+/-}5.7% after one-time sterilization (p<0.001). Breathing and pressure resistance tests indicated no relevant pressure changes between respirators that were used once, twice or thrice. ConclusionThis study shows that selected FFP2-type respirators may be reprocessed for use in primary care, as the tested masks retain their shape, ability to retain particles and breathing comfort after decontamination using a medical autoclave. Strengths and limitations of this study- Pragmatic use of autoclave to sterilize and reuse filter facepiece respirators - Combining clinical and laboratory findings to evaluate the safety in terms of shape, ability to retain particles and breathing comfort - The study is limited in sample size and restricted to selected FFP-2 and FFP-3 respirators - The study is a first of its kind in primary care settings and thus unvalidated - The study does not provide "hard" clinical evidence in terms of a randomized trial (i.e. reprocessed mask versus usual care)

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.

BackgroundIn the context of the ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, the supply of personal protective equipment remains under severe strain. To address this issue, re-use of surgical face masks and filtering facepiece respirators has been recommended; prior decontamination is paramount to their re-use. AimWe aim to provide information on the effects of three decontamination procedures on porcine respiratory coronavirus (PRCV)-contaminated masks and respirators, presenting a stable model for infectious coronavirus decontamination of these typically single-use-only products. MethodsSurgical masks and filtering facepiece respirator coupons and straps were inoculated with infectious PRCV and submitted to three decontamination treatments, UV irradiation, vaporised H2O2, and dry heat treatment. Viruses were recovered from sample materials and viral titres were measured in swine testicle cells. FindingsUV irradiation, vaporised H2O2 and dry heat reduced infectious PRCV by more than three orders of magnitude on mask and respirator coupons and rendered it undetectable in all decontamination assays. ConclusionThis is the first description of stable disinfection of face masks and filtering facepiece respirators contaminated with an infectious SARS-CoV-2 surrogate using UV irradiation, vaporised H2O2 and dry heat treatment. The three methods permit demonstration of a loss of infectivity by more than three orders of magnitude of an infectious coronavirus in line with the FDA policy regarding face masks and respirators. It presents advantages of uncomplicated manipulation and utilisation in a BSL2 facility, therefore being easily adaptable to other respirator and mask types.