Authors: Katelyn E. Zulauf, Alex B. Green, Alex N. Nguyen Ba, Tanush Jagdish, Dvir Reif, Robert Seeley, Alana Dale, and also James E. Kirby https://orcid.org/0000-0003-0392-4500
DOI: https://doi.org/10.1128/mBio.00997-20•
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The significant acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused a severe, global shortage the N95 respirators, i m sorry are crucial to safeguard health treatment providers native infection. Given the modern limitations of the supply chain, it is command to identify effective way of decontaminating, reusing, and also thereby conserving N95 respirator stockpiles. To it is in effective, decontamination must an outcome in sterilization the the N95 respirator without handicap of respirator filtration or user fit. Although many methods of N95 decontamination exist, none are universally accessible. In this work, we define a microwave-generated steam decontamination protocol for N95 respirators for usage in health care systems of every sizes, geographies, and means. Using widely easily accessible glass containers, mesh from commercial create bags, a rubber band, and a 1,100-W commercially available microwave, we created an effective, standardized, and also reproducible way of decontaminating N95 respirators. Use this methodology versus MS2 phage, a very conservative surrogate for SARS-CoV-2 contamination, us report an typical 6-log10 plaque-forming unit (PFU) (99.9999%) and a minimum 5-log10 PFU (99.999%) palliation after a single 3-min microwave treatment. Notably, quantified respirator fit and function were preserved, also after 20 sequential cycles that microwave vapor decontamination. This technique provides a valuable way of efficient decontamination and reuse that N95 respirators by frontline providers facing urgent need.

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IMPORTANCE due to the rapid spread that coronavirus condition 2019 (COVID-19), there is an increasing shortage of protective gear vital to store health treatment providers safe from infection. As of 9 April 2020, the CDC reported 9,282 cumulative instances of COVID-19 among U.S. Health treatment workers (CDC COVID-19 response Team, MMWR Morb Mortal Wkly Rep 69:477–481, 2020, https://doi.org/10.15585/mmwr.mm6915e6). N95 respirators room recommended through the CDC as the ideal method of protection from COVID-19. Back N95 respirators are traditionally single use, the shortages have actually necessitated the require for reuse. Efficient methods of N95 decontamination that do not influence the fit or filtration capability of N95 respirators space essential. Countless methods that N95 decontamination exist; however, none room universally accessible. In this study, we describe an effective, standardized, and also reproducible method of decontaminating N95 respirators utilizing widely obtainable materials. The N95 decontamination method described in this job-related will carry out a valuable source for hospitals, health care centers, and outpatient methods that room experiencing raising shortages of N95 respirators due to the COVID-19 pandemic.
Since the initial cases in Wuhan, China, in so late December 2019, the coronavirus an illness 2019 (COVID-19) pandemic, brought about by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, has resulted in much more than 5.5 million infections and 350,000 deaths an international (1). Transparent this outbreak, the infection and also resultant incapacitation the health treatment providers has been of significant concern (20). Each sick provider contributes to additional nosocomial transmission and also reduces the health treatment system’s capacity to take care of incoming patience volume. One of the greatest threats come the well-being of health care workers is the critical shortage of personal protection equipment. Of particular concern space shortages in devoted N95 respirators.
The nationwide Institute for job-related Safety and also Health (NIOSH) recommends N95 respirators for defense from corpuscle of 2). Across the united States and also worldwide, N95 prices have actually skyrocketed and supplies have actually dwindled. The Centers for condition Control and Prevention (CDC) has actually released unmatched guidance on the conservation, expanded use, and limited reuse of N95 respirators in health treatment settings (https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html and https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html). Effective, economical, accessible, and validated method of decontamination are urgently required.
Several N95 decontamination techniques have actually been validated and also approved because that clinical use. The CDC has actually summarized a selection of methods, consisting of UV germicidal irradiation (UVGI), ethylene oxide, vaporized hydrogen peroxide, moist warmth incubation, and microwave-generated vapor (https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html). The ideal method is one the is at the same time rigorous sufficient to carry out maximal decontamination and also yet gentle enough to impart minimal structural damages to the N95 respirator. Microwave-generated steam is a unique promising an approach because that its potential for daily, affordable, and widespread use. Back microwave-generated steam has been displayed to be efficient in both decontamination and preservation that respirator function, the majority of published protocols count on specialized commercial steam bags which space in limited supply this day or other unstandardized materials easily accessible only in study laboratories (3–7).
Here, together a top quality assurance initiative in ~ our institution, we set out to identify an N95 decontamination technique that would permit repeated use of respirators. To evaluate decontamination, we made use of the Escherichia coli MS2 bacteriophage together a extremely conservative surrogate for serious acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we describe advancement and review of a straightforward microwave vapor decontamination protocol utilizing affordable, readily obtainable materials that achieves highly reliable disinfection of MS2 virus, while maintaining respirator duty for repeated reuse.
To attend to the shortage that N95 respirators the are essential to keep health care workers defended from SARS-CoV-2, we set out to identify an effective method of N95 decontamination. Our goal to be to uncover a decontamination technique accessible to every practitioners in our spread health treatment network, using MS2 phage as a version for SARS-CoV-2. Choose SARS-CoV-2, the MS2 phage is a positive-sense, single-stranded RNA virus. Unequal SARS-CoV-2, the MS2 phage lacks a lipid envelope, make it more resistant to disinfection. Due to its stability, MS2 has been offered to design disinfection the viruses such as norovirus and also Ebola virus (8, 9).
Microwave-generated steam has proven to be an effective an approach of decontamination (3–7). In seeking a platform v widespread availability, we at first tested 2 protocols using common household items. Both protocols affiliated the use of a 10-cm-diameter ceramic mug filled with 60 ml distilled water and also covered through the mesh from a create bag secured with a rubber band, on i m sorry the respirator was suspended directly above the generated vapor (Fig. 1A). In one assay, we inserted the mug inside a ventilated gallon Ziploc bag. In the various other assay, we location the mug straight in the microwave there is no containment. Us then check the ability of both approaches to sterilize N95 coupons (excised 1-cm2 3M 1860 N95 fabric squares) inoculated with 107 PFU of MS2 phage. The inoculation that 107 PFU represents a greater viral pack than any kind of viral droplet a health treatment provider is most likely to conference in the clinical setting (10). ~ 1 min that microwave heavy steam decontamination, we experienced no far-ranging difference in MS2 phage reduction in between the two methods (Fig. 1B). The is important to note that both methods caused a higher than 4-log10 palliation in MS2 titer after only 1 min the microwave treatment. The Ziploc bag, however, melted under this treatment and also posed the risk of heavy steam burns during retrieval that the N95 respirator. Noting same efficacy, we proceeded v the open-container method of vapor decontamination because that all further work.
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FIG 1 N95 respirator microwave vapor decontamination by ceramic mug either within or in the lack of Ziploc containment. (A) photo of ceramic mug decontamination system. A 10-cm-diameter mug to be filled through 60 ml of distilled water and also covered v mesh native a create bag, secured with a rubber band. Triplicate N95 1-cm2 coupons were put on peak of the mesh. The mug to be then put in the microwave one of two people in a sealed, ventilated Ziploc bag or straight into the microwave. (B) ~ a 1-min microwave treatment, through or without Ziploc bag enclosure, or a 60-min treatment v dry 105°C heat, phage to be extracted native N95 coupons and also quantified by plaque assay. Triplicate untreated N95 coupons were included as controls in every assays. There was no far-ranging reduction in plaque titer in between Ziploc bag-enclosed and also open-mug decontamination solution or between dry-heat-treated and also untreated controls (P = 0.9 or p = 0.66, respectively, as determined by analysis of variance (ANOVA) v Holm Sidak posthoc test). PFU, plaque-forming units, a direct measure the viable famous titer; n.s., no significant.
To determine the optimal length of microwave time required for MS2 phage decontamination, we performed a dose-response test using 1-min increments whereby we examined the decontamination of 107 PFU the MS2 ~ above 1-cm2 N95 coupons inserted over an open up mug (as described above). Complying with 3 min of microwave heavy steam treatment, there to be no detectable MS2 phage remaining on the coupons (Fig. 2A). To accurately assess the capability of this an approach to decontaminate all locations of one N95 respirator, we inoculated 107 PFU the MS2 phage top top 10 discrete sections of an N95 respirator (Fig. 2C). Complying with 3 min the treatment, we observed a higher than 4-log10 reduction in PFU on all N95 respirator segments, other than the elastic straps i beg your pardon showed only a 1- come 3-log10 reduction in PFU (Fig. 2D). Due to the restricted diameter the the mug, the elastic straps draped over the edges, and also presumably were minimally exposed to microwave-generated heavy steam (Fig. 2B). Consequently, us hypothesized that direct exposure to steam is essential for effective decontamination and sought to determine a advertisement container of enough diameter come treat an entire respirator.
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FIG 2 N95 respirator decontamination by microwave-generated heavy steam over an open up ceramic mug. (A) Triplicate N95 coupons treated with 107 PFU MS2 were inserted on the mesh-covered ceramic mug and treated because that the indicated durations in an 1,100-W microwave. ~ treatment, phage to be extracted native N95 coupons and also quantified through plaque assay. (B) We next evaluated therapy of an entire N95 respirator top top the mug decontamination system. (C) 107 PFU the MS2 to be spotted top top 10 premarked part of a whole N95 respirator as indicated. (D) ~ a 3-min treatment in an 1,100-W microwave, demarcated pretreated segments measuring 1 cm2 were excised native the respirator, and also MS2 phage was then extracted and quantified by plaque assay. Triplicate untreated precut N95 coupons were included as a manage in every assays. Bars shown are way and conventional deviations the phage titers from every excised segment from a solitary respirator. One asterisk suggests that no viable MS2 were detected. The limit of detection of every assays is 10 PFU. Data displayed are representative of three different respirator experiments.
Ultimately, we selected a generic glass container size at 17 × 17 × 7.5 cm (length × width × height ) that had an opening huge enough to disclose the whole N95 respirator come the vertical shaft of produced steam. Just like the ceramic mug, we secured mesh indigenous a develop bag end the peak of the container through a rubber band and added 60 ml that distilled water to the basin (Fig. 3A and B). We repeated a sterilization time course against 1-cm2 N95 respirator coupons in 1-min increments. ~ 2 min that microwave steam treatment, us were can not to recognize residual viable phage ~ above the coupons (Fig. 3C). This to represent a 1-min reduction in sterilization time contrasted to the ceramic mug decontamination assay, indicating the the glass container is a much more efficient decontamination system.
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FIG 3 N95 respirator decontamination through microwave-generated vapor over an open glass container. (A and B) photo of glass container decontamination system. A 17 cm × 17 cm glass container to be filled with 60 ml the distilled water, spanned with mesh indigenous a create bag, secured v a rubber band. (C) Triplicate N95 respirator coupons inoculated v 107 PFU MS2 phage, inserted on the mesh-covered container, and also treated for indicated times in one 1,100-W microwave. After ~ treatment, MS2 phage was extracted native N95 coupons and also quantified by plaque assay. (D) 107 PFU of MS2 phage was spotted ~ above 10 various premarked locations on a N95 respirator together indicated. (E) The whole N95 respirator to be then treated for 3 min as presented in panel B in one 1,100-W microwave. Demarcated segments measuring 1 cm2 encompassing the area the inoculation to be excised from the respirator, and MS2 phage to be extracted and quantified through plaque assay. Triplicate untreated precut N95 coupons were contained as a control in all assays. Data shown are the way and typical deviations the plaque titers indigenous a solitary respirator and are representative that three different experiments. In one experiment, no viable PFU to be detected from all excised segment (data not shown). One asterisk suggests that no viable MS2 to be detected. The border of detection of every assays is 10 PFU.
We next examined the capability of the glass container come sterilize a whole N95 respirator. As defined above, we inoculated 10 sections of one N95 respirator through MS2 phage and treated the respirator for 3 min over the container mechanism (Fig. 3D). Just 20% of the sampled sections displayed residual phage, and of this sections, each displayed a 5-log10 reduction in viable phage (Fig. 3E). In among three trials on different N95 respirators, over there was complete sterilization on every sampled sections with no detectable PFU staying posttreatment. Importantly throughout all assays, viral fill was reduced by an mean of 6-log10 PFU (99.9999% with a minimum that 5-log10 PFU <99.999%>) reduction. This results indicate that open-container therapy is an effective method of N95 decontamination.
Since that is important that any type of decontamination method not alleviate the filtration or truth of N95 respirators, us examined N95 respirator fit and duty after sequential treatments. ~ 1, 5, or 20 3-min treatment cycles, no damages was noticeable in the integrity of the respirators or their component components (i.e., straps, foam fittings, nosepiece). Additionally, no odors were detected posttreatment, i beg your pardon is consistent with previous reports of microwave-generated vapor decontamination (4). Furthermore, Quantitative Respirator fit Testing conducted with a PortaCount fit Tester 8038, in maintaining with the work-related Safety and also Health Administration’s (OSHA) measures (11), did no demonstrate any kind of changes in respirator power after 1, 5, or 20 treatment cycles. Throughout all 7 exercises in the OSHA-accepted fit test protocol, we observed component fit aspect scores in overfill of the 100 fit factor minimum and overall fit factor values the >175 ~ 1, 5, and 20 treatment cycles. Cumulatively, this data show that fit, seal, and filtration to be preserved even after 20 consecutive treatments.
Last, posttreatment respirators walk not present a significant change in fixed (5). This is likely as result of the reality that the N95 respirator is suspended over the heavy steam and is no in any sustained, direct contact with water. The absence of water retention method little come no dry time is required posttreatment prior to N95 respirator use.
In summary, we determined an effective an approach of N95 decontamination through microwave-generated heavy steam utilizing universally accessible materials. Our method resulted in almost complete sterilization after just 3 min that treatment and did not show up to affect the integrity of N95 filtration or fit with recurring treatment.
Due to the quick spread the COVID-19, hospitals, health care centers, and outpatient practices are experiencing increasing shortages of protective gear crucial to keep health care providers for sure from infection. Dedicated N95 respirators room recommended by the CDC for security from COVID-19 (https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html and https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html). Back N95 respirators are usually recommended only for solitary use, the major shortages have actually necessitated reuse. During patient care, however, the surface of N95 respirators are most likely contaminated by virus containing droplets and aerosols. Recent work has actually demonstrated the SARS-CoV-2 can survive on surface for up to 72 h (12). Without mindful doffing an approach and decontamination, provided N95 respirators can serve as contagious fomites and also pose a risk to health care providers. In order to conserve it is provided and carry out protection come health treatment workers, there has actually been an initiative to identify viable techniques of N95 decontamination to assistance safe reuse.
The CDC reports a variety of decontamination methods, including UV germicidal Irradiation (UVGI), ethylene oxide, vaporized hydrogen peroxide, moist heat incubation, and microwave-generated steam (https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html). However, these approaches have far-ranging limitations. UVGI is restricted by innate shadow impacts of a irradiate source, and variability in dosages as result of bulb age and different communication constructions (13). Ethylene oxide is efficacious in eradicating microbial contamination however is likewise a well-known carcinogen and teratogen, and also exposure has been associated with neurologic dysfunction (14). Vaporized hydrogen peroxide (VHP) is highly effective, killing better than 99.9999% of surrogate microbial contaminants (a 6-log10 reduction), while preserving respirator filtration role (15). However, the modern technology necessary because that VHP is limited to larger health care systems that have the right to afford the forced equipment. Therefore, there is one urgent require for viable methods of decontamination that are safe, effective, and available in varied clinical settings.
In order to determine a generally easily accessible N95 respirator decontamination method, we focused our initiatives on microwave-generated heavy steam decontamination. Microwaves space ubiquitous, and previous studies have actually demonstrated the efficiency of microwave vapor decontamination. Come date, however, studies evaluating microwave-generated steam decontamination have actually employed both specific and laboratory-generated materials (e.g., pipette tip boxes, modification reservoirs, commercial steam bags, etc.) that might not it is in generally accessible or conveniently reproduced (3–7).
The goal of this occupational was to identify a extensively accessible, microwave-generated steam decontamination method. To this effect, we utilized only usual household items. We an initial examined whether contained vapor was much more effective 보다 an open heavy steam vessel. Together commercial microwave sterilization bags have previously demonstrated efficiency, we examined if common Ziploc bags can provide similar benefits (5). Return Ziploc bag-enclosed decontamination was effective, our results indicated that the is a more cumbersome system and also containment could be dispensed through entirely. Furthermore, Ziploc bags started to melt as soon as exposed to an ext than 1 min the microwave-generated vapor and make the danger of heat burns from contained steam, making the enclosed method less compelling.
With extr study, we discovered that use of a generic glass container measure up 17 × 17 × 7.5 cm (L × W × H) resulted in the many efficient and also practical N95 respirator decontamination system. Utilizing this method, us observed virtually complete sterilization of the N95 respirator after ~ a solitary 3-min treatment. On average, we discovered a 6-log10 palliation in viable MS2 phage through a minimum that a 5-log10 reduction. Throughout decontamination treatments, us positioned the N95 respirator through its convex surface ar pointed downward, ~ above the mesh-covered container, maximizing steam exposure. Placement to be otherwise made there is no regard to details orientation of the respirator, simulating real people application. Posttreatment water retention by the N95 respirator was no detected, removed a require for drying time prior to reuse. Importantly, this technique was validated for usage of 20 times on a single respirator without detrimental result on respirator truth or fit. In contrast, a recent preprint demonstrated the fit and seal truth was endangered in UV- and also heat-treated N95 respirators after 3 treatment cycles and in ethanol-treated respirators after ~ 2 therapy cycles (16). Given these findings, decontamination by microwave-generated steam may administer an appropriate solution for wide N95 respirator reuse, v minimal treatment duration, minimal posttreatment processing, and maximal reuse potential.
The MS2 bacter was provided as a model of SARS-CoV-2 in this study. It listed a facile device for fast quantitative evaluation of respirator disinfection. Importantly, MS2, similar to SARS-CoV-2, is a positive-sense single-stranded RNA virus. However, there room some important distinctions. MS2 is a nonenveloped virus encased in a protective icosahedral protein capsid. SARS-CoV-2, in contrast, is a lipid-enveloped virus, do it much more susceptible to disinfection methods. Previously, MS2 has actually been provided as a surrogate because that protein capsid-protected noroviruses and also for enveloped Ebola virus, and also it has been reported to be significantly more resistant come disinfectant 보다 both (8, 17). These differences were highlighted in our existing study by monitoring of complete resistance of MS2 come dry heat inactivation at 105°C for 60 min (Fig. 1B) contrasted with previously reported finish inactivation of SARS-CoV-2 by 70°C dry warmth treatment for the very same duration (16). Therefore, the substantial reduction in viable MS2 through microwave vapor decontamination gives confidence in an suitable safety margin for SARS-CoV-2 decontamination and also suggests the extr benefit the disinfection of various other viruses the may likewise contaminate respirators during reuse.
Our N95 decontamination device uses only commonly available materials: a glass container, mesh native a produce bag that can be discovered at any type of grocery store, and a rubber band, and a usual household 1,100-W or 1,150-W microwave. All microwaves provided in this study had actually a turntable to enable rotation while heater (Fig. 1B and also C and also Fig. 3A), a function that likely promotes uniform heating and heavy steam production. That is important to note that the microwave therapy did not an outcome in sparks even when there to be metal current on the N95, which is continual with previous reports (4). Ours decontamination protocol was validated v a glass container, and also it is possible that heavy steam generation and also results would certainly be impacted using containers do of other materials.
We began our examine using a ceramic coffee mug to generate steam. However, there to be several restrictions to this method. Notably, the sizes of ceramic mugs vary widely, make this an approach hard come standardize. Although us observed complete sterilization the the 1-cm2 coupons ~ above the ceramic coffee mug, we did no observe a similar an outcome using the whole N95 respirator (Fig. 2) where significant quantities of viable virus stayed posttreatment (102 come 106 PFU). In contrast, the bigger surface area detailed by the glass container led to nearly complete sterilization at all locations. Furthermore, the 10-cm-diameter mug opened was tho too tiny to suspend the elastic straps of the respirator above the mug orifice. This led to inefficient decontamination of the elastic straps, in contrast to findings using the bigger glass container. Our research highlights the have to examine the entirety respirator because that disinfection rather than just small coupons isolated native the filtration material, as has actually been typically performed in N95 respirator disinfection studies.
Several restrictions and added points must be noted. First, real-world usage of N95 respirators in mix with microwave treatment may accelerate ns of mask integrity. Therefore, the capability to preserve duty during 20 microwave sterilization treatments must be construed with caution. Second, in this study, distilled water was provided for microwave steam generation for assay standardization. Insanity water is much more generally easily accessible and is less likely 보다 distilled water come superheat and an outcome in potential scalding. Third, round containers may potentially boost homogeneity of heavy steam production (https://products.geappliances.com/appliance/gea-support-search-content?contentId=18800, accessed 26 might 2020). Accordingly, we mean that ring containers would also suitably decontaminate masks; however, we did not especially test this alternative.
Taken together, this work demonstrates the effectiveness of one affordable, simple technique of N95 respirator decontamination. The usage of typical household items and the capacity to resterilize the respirator multiple times without detriment to filtration or fit administer a compelling disinfection method that must prove generally obtainable to varied settings, consisting of outpatient practices, frontline providers, and also remote clinical settings.
MS2 bacteriophage was recovered from societies of Escherichia coli stress, overload W1485 using traditional phage isolation techniques (18). We added 2 ml that 109 PFU/ml MS2 to a 50-ml culture of E. Coli W1485 in exponential step (optical thickness at 600 nm of ∼0.2). Overnight growth resulted in MS2-mediated lysis of farming cells. This suspension was centrifuged at 4,000 × g for 10 min and filtered v a 0.22-μm polyethylene filter. The filtrate was then assessed for viral titer and readjusted to a last concentration the 109 PFU/ml for all downstream experiments.
Decontamination test were carried out using 3M N95 respirators (model 1860 Health care Particulate Respirator and Surgical Mask). Excised 1-cm2 coupons or whole N95 respirators to be treated with 10 μl that 109 PFU/ml MS2, resulting in an ∼107 PFU inoculation. As soon as a entirety respirator to be treated, 10 sections to be demarcated and inoculated, consisting of two clues on the elastic straps. The inoculated N95 coupons and also whole respirators to be then permitted to dry within a biosafety cabinet for 2 h. When dried, precut triplicate N95 respirator coupons were gotten rid of to quantify viral load prior to intervention.
Mesh from develop bags (multiple variants were made use of in this study) to be secured throughout the height of one of two people a ceramic mug or glass container v rubber bands. The mug utilized in this study was 10 cm in diameter. The glass container (Snapware 4-cup food warehouse container made through Pyrex glass) is around 17 cm × 17 cm × 7.5 cm (6.5 in × 6.5 in × 3 in). Both the mug and glass container to be filled v 60 ml (1/4 cup) of distilled water for steam generation. N95 coupons and also respirators were placed outward dealing with side down, onto the mesh, for direct suspension above the steam (Fig. 1C and 3B). As soon as a Ziploc bag was utilized, a 2-cm cleft was reduced in the upper right side of the bag to vent overabundance steam. The N95 respirator coupons and whole respirators were then treated because that the suggested time in either a 1,150-W or a 1,100-W microwave. Both microwaves utilized in this study contain a turntable because that uniform heating. It is remarkable that results were consistent in between both microwaves used in this study.
For dry warm treatment, 1-cm2 N95 respirator coupons were exposed to 105°C dry heat for 60 min in a hybridization oven.
Viral fill on pre- and also postintervention N95 respirators and coupons was measured using developed plaque assay protocols (18, 19). For whole respirators, each treated area to be cut and also removed indigenous the N95 respirator and processed individually. Each piece was submerged in 1 ml LB broth and also vortexed because that 1 min to elute MS2 phage. The LB suspension to be then serially diluted, following which 100 μl from each of the phage dilutions was mixed with 100 μl that exponential-phase organize E. Coli W1485 cells. This mixture to be then vortexed through 3 ml of LB peak agar (0.6% agar ) and also spread on LB agar key (1.5% agar ). Every plates were incubated at 37°C overnight to enable bacterial lawns and viral plaques come grow. Plaques were quantified, and also the total PFU burden was calculated. The border of detection of this assay to be 10 PFU.
N95 respirators cure 1, 5, and also 20 continually times to be examined for as whole integrity and also filtration performance. There to be not any type of observed changes in comfort, breath effort, or odor in between control and also microwave-treated respirators. Quantitative respirator fit testing was performed using a PortaCount agree 8038 to the right Tester (TSI Incorporated). Trial and error was carried out in accordance v the definitions, thresholds, and also protocols for respiratory tract protective devices outlined in OSHA 29CFR1910.134 (https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134). Salt chloride was provided as a nonhazardous test aerosol using a TSI fragment generator, developing particles through a in the name diameter of 0.04 μm. The fit variable was calculated automatically on the PortaCount pro 8038 fit Test. The fit variable represents the proportion of the median ambient aerosol concentration to that measured inside the respirator throughout each exercise. For testing, a sample port was installed in the breath zone of the respirator utilizing N95 fit test adaptors. The respirator to be donned because that 5 min before the quantitative check to inspect for adequacy the respirator fit, do user seal checks, and purge particles trapped within the respirator. The fit check entailed the 7 OSHA-approved exercises, each as much as 1 min in duration, consisting of normal breathing, deep breathing, head side to side, head up and down, talking, grimacing (15 s only), and also bending over. The PortaCount agree Fit Tester calculate the fit factor for every exercise, and an overall, averaged fit factor. Happen entailed a minimum fit factor of 100 on separation, personal, instance exercises and overall score alike. In keeping with the to work manual, the PortaCount agree Fit Tester underwent daily maintenance check throughout the duration of experimentation to ensure consistent quality monitoring.
We quantified water absorption right into N95 respirators throughout the microwave vapor decontamination treatment as defined previously (5). We measured the mass of N95 respirators pretreatment and immediately posttreatment making use of an analytical balance. Us subtracted the pretreatment mass native the posttreatment come quantify the amount of water absorption. In every assays, there was

ACKNOWLEDGMENTS


We give thanks to the activities of Michael Baym at Harvard clinical School for the generosity gift that the MS2 phage and the host E. Coli strain and also Thea Brennan-Krohn for crucial review that the manuscript.
K.E.Z. Was sustained by the nationwide Institute of Allergy and Infectious illness training provide (T32AI007061). The content is specifically the obligation of the authors and does no necessarily represent the main views that the national Institutes the Health.

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