N95 Filtering Facepiece Respirators Models Research Articles

Using the Number of N95® Filtering Facepiece Respirator Models as an Indicator of Supply Chain Stability in a US Health-Care System.

Personal protective equipment (PPE) supply chain disruptions force US health-care entities to adopt conservation strategies such as procurement from different respirator manufacturers. This research seeks to better understand how the number of respirator models on hand can serve as an indicator of N95 filtering facepiece respirator (FFR) supply chain stability or disruption. Researchers looked at differences in the mean number of N95 FFR models, averaged weekly, from 10 hospitals in a health-care system over 15 wk from June 1 to September 10, 2020. Participating hospitals entered near-daily PPE inventory data by manufacturer and model number. A linear mixed effect model was run in SPSS v. 26 using a random intercept for hospitals, with week as a fixed predictor and mean number of respirator models (averaged weekly) on hand as the dependent variable. Each week showed a small but significant effect compared with the past week (P < 0.001), where the average weekly number of respirator models on hand decreased. The limited data may indicate a resolution of supply chain disruptions and warrant further investigation. Consequently, the number of respirator models may be applicable as an indicator of supply chain stability and be more easily ascertained and tracked by health-care entities.

Filtration performance of three models of N95 filtering facepiece respirators following clinical usage and vaporized hydrogen peroxide decontamination

N95 filtering facepiece respirators (FFRs) are essential personal protective equipment (PPE) for protecting healthcare workers from airborne pathogens. To perform the first large-scale evaluation of particulate filtration efficiency (PFE) of three models of N95 FFRs following clinical usage and vaporized hydrogen peroxide (VHP) decontamination. Three variables were assessed for effect on PFE following VHP decontamination: VHP sterilizer model, N95 respirator model, and prior N95 clinical usage. The VHP sterilizer model and N95 FFR model impacted PFE performance. Worn N95 FFRs had a 91% lower odds of exhibiting ≥95% PFE compared with the control. This work highlights the importance of validating any N95 FFR decontamination programme in its entirety, including prior clinical usage.

Assessing the Fit of N95 Filtering Facepiece Respirators Fitted with an Ear Loop Strap System: A Pilot Study.

Throughout the COVID-19 pandemic, hundreds of millions of people worldwide have become new users of respiratory protective devices. Facemasks and KN95 respirators utilizing an ear loop straps system (ELSS) have recently become popular among occupational and non-occupational populations. Part of this popularity is due to the ease of wearability as compared with traditional devices utilizing two headbands, one worn over the head and the other behind the neck—a universal strap system used in NIOSH-certified N95 filtering facepiece respirators (FFRs). Some users convert the two-strap configuration to an adjustable ELSS. The first objective of this pilot study was to quantitatively characterize how such a conversion impacts the respirator fit. Additionally, a novel faceseal (NFS) technology, which has been previously demonstrated to enhance the fit of N95 FFRs, was deployed to modify the ELSS-converted N95 FFRs. The second objective of this study was to quantify the fit improvement that results from adding the NFS to the ELSS. The study was conducted by performing the Occupational Safety and Health Administration (OSHA)-approved quantitative fit testing (QNFT) on 16 human subjects featuring different facial shapes and dimensions. Three models of cup-shaped N95 FFRs were tested in three versions: the standard version with manufacturer’s strap system, the ELSS-converted, and the ELSS-converted version modified by adding the NFS. QNFT demonstrated that the fit of an N95 FFR featuring the traditional/standard headbands strap system is negatively impacted when this system is converted to an ELSS. The fit of an ELSS-converted respirator can be significantly improved by the addition of the NFS. We found that the FFR model and the strap system version are significant factors affecting the QNFT-determined respirator fit factor (FF), as well as the OSHA QNFT pass rate (FF ≥100). The findings suggest that the current NFS, if further improved, has a potential for developing a ‘universally fitting’ ELSS-equipped N95 FFR that can be used by the general public, the vast majority of whom do not have access to OSHA fit requirements.

Effect of UV-C germicidal irradiation (UVGI) on the structural integrity of N95 and KN95 respirators

This study focuses on reprocessing a group of filtering facepiece respirators (FFR) using ultraviolet germicidal irradiation (UVGI). The aim is to explore the possibility of disinfecting selected KN95 FFRs, in comparison with the N95 FFRs, and assess their viability for reusage. For this purpose, five models of unused N95 and KN95 FFR models obtained from the hospital were exposed to UV-C light using a customized UVGI chamber. The material integrity of treated FFRs was examined in terms of particle penetration and strap tension. The surface morphology of all models is inspected to determine the visible changes of each FFR upon exposure to 1–100 cycles (1 cycle is equivalent to 1 J/cm2 UV dose). The penetration test results indicate that the physical properties of the KN95 and N95 FFRs remain within permissible limits despite being reprocessed by up to 100 cycles (100 J/cm2). Using a microscope, the physical observations also reveal that no visible damage can be seen even after 100 J/cm2 exposure. Apart from the filter bodies, the tension of each strap was also found to not be significantly affected by UV radiation by at least 10 disinfection cycles (10 J/cm2). This confirms that KN95, as well as N95 FFRs, can be subjected to UV treatment as a means of disinfection.

Persistence of SARS-Co-V-2 on N95 filtering facepiece respirators: implications for reuse

In response to the shortage of N95 filtering facepiece respirators for healthcare workers during the COVID-19 pandemic, the Centers for Disease Control and Prevention issued guidance for extended use and limited reuse of N95 FFRs to conserve supply. Previously worn N95 filtering facepiece respirators can serve as a source of pathogens, which can be transferred to the wearer while doffing and donning a respirator when practicing reuse. When practicing limited filtering facepiece respirators reuse, to reduce the risk of self-contamination, the Centers for Disease Control and Prevention recommends storing filtering facepiece respirators for five days between uses to allow for the decay of viable pathogens including SARS-CoV-2. This study assesses the persistence of the SARS-CoV-2 strain USA-WA1/2020 on N95 filtering facepiece respirators under controlled storage conditions for up to 5 days to inform the Centers for Disease Control and Prevention guidance. Coupons excised from six N95 filtering facepiece respirator models and glass slide coverslips were inoculated with the virus in a defined culture medium and in human saliva and stored at 20 °C and 20%, 45%, and 75% relative humidity. Statistically significant differences in SARS-CoV-2 half-lives were measured among the tested humidity levels with half-lives decreasing from an average of approximately 30 hr at 20% relative humidity to approximately 2 hr at 75% relative humidity. Significant differences in virus half-lives were also observed between the culture medium and saliva suspension media at 20% and 45% relative humidity with half lives up to 2.9 times greater when the virus was suspended in cell culture medium. The 5-day storage strategy, assessed in this study, resulted in a minimum of 93.4% reduction in viable virus for the most challenging condition (20% relative humidity, cell culture medium) and exceeding 99% reduction in virus at all other conditions.

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

ObjectivesThere are currently no studies that have examined whether one dosage can be uniformly applied to different respirator types to effectively decontaminate SARS-CoV-2 on N95 filtering facepiece respirators (FFRs). Health care workers have been using this disinfection method during the pandemic. Our objective was to determine the effect of UVC on SARS-CoV-2 inoculated N95 respirators and whether this was respirator material/model type dependent. MethodsFour different locations (facepiece and strap) on five different N95 FFR models (3M 1860, 8210, 8511, 9211; Moldex 1511) were inoculated with a 10 μL drop of SARS-CoV-2 viral stock (8 × 107 TCID50/mL). The outside-facing and wearer-facing surfaces of the respirators were each irradiated with a dose of 1.5 J/cm2 UVC (254 nm). Viable SARS-CoV-2 was quantified by a median tissue culture infectious dose assay (TCID50). ResultsUVC delivered using a dose of 1.5 J/cm2, to each side, was an effective method of decontamination for the facepieces of 3M 1860 and Moldex 1511, and for the straps of 3M 8210 and the Moldex 1511. ConclusionThis dose is an appropriate decontamination method to facilitate the reuse of respirators for healthcare personnel when applied to specific models/materials. Also, some straps may require additional disinfection to maximize the safety of frontline workers. Implementation of widespread UVC decontamination methods requires careful consideration of model, material type, design, and fit-testing following irradiation.

Multicycle Autoclave Decontamination of N95 Filtering Facepiece Respirators.

Introduction:During pandemic situations like the one caused by the emergent coronavirus SARS-CoV-2, healthcare systems face the challenge of limited personal protective equipment and impaired supply chains. This problem poses a threat to healthcare workers, first responders, and the public, which demands solutions that can span the gap between institutional shortages and resupplies.Objectives:To examine the efficacy of autoclave-based decontamination for the reuse of single-use surgical masks and N95 filtering facepiece respirators (FFRs). This method is the most readily available form of decontamination in the hospital and laboratory settings.Methods:Three models of N95 FFRs and two procedural masks were evaluated in this study. A moist heat autoclave using four different autoclave cycles: 115°C for one hour, 121.1°C for 30 minutes, 130°C for two minutes, and 130°C for four minutes was used. After the autoclave process, the FFRs were NIOSH fit tested and particle counting was performed for both coarse particles of 5 micrometers (µM) and fine particles from 0.1µM to 1.0µM.Results:We observed negligible alterations in the functionality and integrity of 3M 1805 and 3M 1870/1870+ N95 FFRs after three autoclave cycles. Surgical masks also showed minimal changes in functionality and integrity. The 3M 1860 FFR failed fit test after a single autoclave decontamination cycle.Discussion and Conclusion:The study finds that specific surgical masks and N95 FFR models can withstand autoclave decontamination for up to three cycles. Additionally, the autoclave cycles tested were those that could be readily achieved by both clinical and research institutions.

Effectiveness of N95 Facepiece Respirators in Filtering Aerosol Following Storage and Sterilization

ABSTRACT The use of electret N95 filtering facepiece respirators (N95FFRs) after prolonged storage or treatment can reduce the expense of buying non-expired N95 and thus enable developing and developed countries to optimize their use of limited resources to against airborne particles and diseases, such as coronavirus disease 2019 (COVID-19). The filtration performance of five N95FFR models following long-term storage, removal of charge using isopropanol alcohol (IPA), autoclaving, or treatment with gamma-radiation was assessed using a TSI 8130 automated filter tester. Statistically significant differences were found in the penetration (P), pressure drop (Δp) and quality factor (qf) between non-expired and expired N95 models 3M-8210 and 3M-8511. A statistically significant linear correlation was also obtained between the N95 penetration ratio (PR) and the difference between year of manufacture and time of test (DYM). The PR of N95 was more strongly influenced by eliminating the charge (for extremely out-of-date respirators) on the electret filter than by the DYM. Sterilization by gamma irradiation increased the P into non-expired and expired N95FFR models (p < 0.05), reducing their qf. The qf of all N95FFR models, except UVEX-3200, was strongly affected by gamma irradiation, the removal of charge using IPA, autoclaving, and storage in that order. All expired models maintained acceptable filtration performance and still could be used to collect aerosol effectively, even though models 3M-8511 and 3M-1860 had been manufactured up to 13 years previously. As the COVID-19 outbreaks in 2019 and is getting worse in 2020, these data are useful in developing a global stockpiling strategy to maximize the longevity of N95FFRs for public health and healthcare workers. However, the aging of the straps and seal materials (rubbers, plastics) of the N95FFRs may affect their fit factor and effectiveness.

Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators

Safe and effective decontamination and reuse of N95 filtering facepiece respirators (FFRs) has the potential to significantly extend FFR holdings, mitigating a potential shortage due to an influenza pandemic or other pandemic events. Ultraviolet germicidal irradiation (UVGI) has been shown to be effective for decontaminating influenza-contaminated FFRs. This study aims to build on past research by evaluating the UVGI decontamination efficiency of influenza-contaminated FFRs in the presence of soiling agents using an optimized UVGI dose. Twelve samples each of 15 N95 FFR models were contaminated with H1N1 influenza (facepiece and strap), then covered with a soiling agent-artificial saliva or artificial skin oil. For each soiling agent, 3 contaminated FFRs were treated with 1 J/cm2 UVGI for approximately 1 minute, whereas 3 other contaminated FFRs remained untreated. All contaminated surfaces were cut out and virus extracted. Viable influenza was quantified using a median tissue culture infectious dose assay. Significant reductions (≥3 log) in influenza viability for both soiling conditions were observed on facepieces from 12 of 15 FFR models and straps from 7 of 15 FFR models. These data suggest that FFR decontamination and reuse using UVGI can be effective. Implementation of a UVGI method will require careful consideration of FFR model, material type, and design.

Resistance to synthetic blood penetration of National Institute for Occupational Safety and Health-approved N95 filtering facepiece respirators and surgical N95 respirators

BackgroundSurgical N95 filtering facepiece respirators (FFRs), certified by the National Institute for Occupational Safety and Health (NIOSH) as a respirator and cleared by the Food and Drug Administration (FDA) as a surgical mask, are often used to protect from the inhalation of infectious aerosols and from splashes/sprays of body fluids in health care facilities. A shortage of respirators can be expected during a pandemic. The availability of surgical N95 FFRs can potentially be increased by incorporating FDA clearance requirements in the NIOSH respirator approval process.MethodsFluid resistance of NIOSH-approved N95 FFRs, and FDA-cleared surgical N95 FFRs and surgical masks was tested using the ASTM F1862 method at 450 and 635 cm/sec velocities and compared with the results from a third-party independent laboratory. Blood penetration through different layers of filter media of masks were also analyzed visually.ResultsFour N95 FFR models showed no test failures at both velocities. The penetration results obtained in the NIOSH laboratory were comparable to those from the third-party independent laboratory. The number of respirator samples failing the test increased with increasing test velocity.ConclusionsThe results indicate that several NIOSH-approved N95 FFR models would likely pass FDA clearance requirements for resistance to synthetic blood penetration.

Effects of Ultraviolet Germicidal Irradiation (UVGI) on N95 Respirator Filtration Performance and Structural Integrity

The ability to disinfect and reuse disposable N95 filtering facepiece respirators (FFRs) may be needed during a pandemic of an infectious respiratory disease such as influenza. Ultraviolet germicidal irradiation (UVGI) is one possible method for respirator disinfection. However, UV radiation degrades polymers, which presents the possibility that UVGI exposure could degrade the ability of a disposable respirator to protect the worker. To study this, we exposed both sides of material coupons and respirator straps from four models of N95 FFRs to UVGI doses from 120–950 J/cm2. We then tested the particle penetration, flow resistance, and bursting strengths of the individual respirator coupon layers, and the breaking strength of the respirator straps. We found that UVGI exposure led to a small increase in particle penetration (up to 1.25%) and had little effect on the flow resistance. UVGI exposure had a more pronounced effect on the strengths of the respirator materials. At the higher UVGI doses, the strength of the layers of respirator material was substantially reduced (in some cases, by >90%). The changes in the strengths of the respirator materials varied considerably among the different models of respirators. UVGI had less of an effect on the respirator straps; a dose of 2360 J/cm2 reduced the breaking strength of the straps by 20–51%. Our results suggest that UVGI could be used to effectively disinfect disposable respirators for reuse, but the maximum number of disinfection cycles will be limited by the respirator model and the UVGI dose required to inactivate the pathogen.

Protection Factor for N95 Filtering Facepiece Respirators Exposed to Laboratory Aerosols Containing Different Concentrations of Nanoparticles

A previous study used a PortaCount Plus to measure the ratio of particle concentrations outside (C out) to inside (C in) of filtering facepiece respirators (FFRs) worn by test subjects and calculated the total inward leakage (TIL) (C in/C out) to evaluate the reproducibility of the TIL test method between two different National Institute for Occupational Safety and Health laboratories (Laboratories 1 and 2) at the Pittsburgh Campus. The purpose of this study is to utilize the originally obtained PortaCount C out/C in ratio as a measure of protection factor (PF) and evaluate the influence of particle distribution and filter efficiency. PFs were obtained for five N95 model FFRs worn by 35 subjects for three donnings (5 models × 35 subjects × 3 donnings) for a total of 525 tests in each laboratory. The geometric mean of PFs, geometric standard deviation (GSD), and the 5th percentile values for the five N95 FFR models were calculated for the two laboratories. Filter efficiency was obtained by measuring the penetration for four models (A, B, C, and D) against Laboratory 2 aerosol using two condensation particle counters. Particle size distribution, measured using a Scanning Mobility Particle Sizer, showed a mean count median diameter (CMD) of 82 nm in Laboratory 1 and 131 nm in Laboratory 2. The smaller CMD showed relatively higher concentration of nanoparticles in Laboratory 1 than in Laboratory 2. Results showed that the PFs and 5th percentile values for two models (B and E) were larger than other three models (A, C, and D) in both laboratories. The PFs and 5th percentile values of models B and E in Laboratory 1 with a count median diameter (CMD) of 82 nm were smaller than in Laboratory 2 with a CMD of 131 nm, indicating an association between particle size distribution and PF. The three lower efficiency models (A, C, and D) showed lower PF values than the higher efficiency model B showing the influence of filter efficiency on PF value. Overall, the data show that particle size distribution and filter efficiency influence the PFs and 5th percentile values. The PFs and 5th percentile values decreased with increasing nanoparticle concentration (from CMD of 131 to 82 nm) indicating lower PFs for aerosol distribution within nanoparticle size range (<100 nm). Further studies on the relationship between particle size distribution and PF are needed to better understand the respiratory protection against nanoparticles.

A Quantitative Assessment of the Total Inward Leakage of NaCl Aerosol Representing Submicron-Size Bioaerosol Through N95 Filtering Facepiece Respirators and Surgical Masks

Respiratory protection provided by a particulate respirator is a function of particle penetration through filter media and through faceseal leakage. Faceseal leakage largely contributes to the penetration of particles through a respirator and compromises protection. When faceseal leaks arise, filter penetration is assumed to be negligible. The contribution of filter penetration and faceseal leakage to total inward leakage (TIL) of submicron-size bioaerosols is not well studied. To address this issue, TIL values for two N95 filtering facepiece respirator (FFR) models and two surgical mask (SM) models sealed to a manikin were measured at 8 L and 40 L breathing minute volumes with different artificial leak sizes. TIL values for different size (20–800 nm, electrical mobility diameter) NaCl particles representing submicron-size bioaerosols were measured using a scanning mobility particle sizer. Efficiency of filtering devices was assessed by measuring the penetration against NaCl aerosol similar to the method used for NIOSH particulate filter certification. Results showed that the most penetrating particle size (MPPS) was ∼45 nm for both N95 FFR models and one of the two SM models, and ∼350 nm for the other SM model at sealed condition with no leaks as well as with different leak sizes. TIL values increased with increasing leak sizes and breathing minute volumes. Relatively, higher efficiency N95 and SM models showed lower TIL values. Filter efficiency of FFRs and SMs influenced the TIL at different flow rates and leak sizes. Overall, the data indicate that good fitting higher-efficiency FFRs may offer higher protection against submicron-size bioaerosols.

Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus

Decontamination, cleaning, and reuse of filtering facepiece respirators (FFRs) has been proposed to mitigate an acute FFR shortage during a public health emergency. Our study evaluates the ability of commercially available wipe products to clean FFRs contaminated with either infectious or noninfectious aerosols. Three models of surgical N95 FFRs were contaminated with aerosols of mucin or viable Staphylococcus aureus then cleaned with hypochlorite, benzalkonium chloride, or nonantimicrobial wipes. After cleaning, FFRs were separated into components (nose pad, fabrics, and perforated strip), and contaminants were extracted and quantified. Filtration performance was assessed for cleaned FFRs. Mucin removal was <1 log for all wipe products on all components. Inert wipes achieved ∼1-log attenuation in viable S aureus on fabrics from all FFR models--removal was less effective from nose pads and perforated edges. Both antimicrobial wipes achieved 3-5-log attenuation on most components, with smaller reductions on nose pads and greater reductions on perforated strips. Particle penetration following cleaning yielded mean values <5%. The highest penetrations were observed in FFRs cleaned with benzalkonium chloride wipes. FFRs can be disinfected using antimicrobial wipe products, but not effectively cleaned with the wipes evaluated in this study. This study provides informative data for the development of better FFRs and applicable cleaning products.

Fitting Characteristics of N95 Filtering-Facepiece Respirators Used Widely in China

BackgroundMillions of people rely on N95 filtering facepiece respirators to reduce the risk of airborne particles and prevent them from respiratory infections. However, there are no respirator fit testing and training regulations in China. Meanwhile, no study has been conducted to investigate the fit of various respirators. The objective of this study was to investigate whether people obtained adequate fit when wearing N95 filtering facepiece respirators (FFRs) used widely in China.MethodsFifty adult participants selected using the Chinese respirator fit test panel donned 10 common models of N95 FFRs. Fit factors (FF) and inward leakage were measured using the TSI PortaCount Plus. Each subject was tested with three replications for each model. A subject was considered to pass the fit test when at least two of the three FFs were greater than 100. Two models were conducted fit tests before and after training to assess the role of training.ResultsThe geometric mean FFs for each model and trained subjects ranged from <10 to 74.0. The fifth percentile FFs for only two individual respirator models were greater than 10 which is the expected level of performance for FFRs. The passing rates for these two models of FFRs were 44.7% and 20.0%. The passing rates were less than 10.0% for the other eight models. There were 27 (54%) participants who passed none of the 10 FFRs. The geometric mean FFs for both models when the subjects received training (49.7 and 74.0) were significantly larger than those when the same group of subjects did not receive any training (29.0 and 30.9) (P<0.05).ConclusionsFFRs used widely in China should be improved according to Chinese facial dimensions. Respirator users could benefit from respirator training and fit testing before using respirators.

Development of an Advanced Respirator Fit-Test Headform

Improved respirator test headforms are needed to measure the fit of N95 filtering facepiece respirators (FFRs) for protection studies against viable airborne particles. A Static (i.e., non-moving, non-speaking) Advanced Headform (StAH) was developed for evaluating the fit of N95 FFRs. The StAH was developed based on the anthropometric dimensions of a digital headform reported by the National Institute for Occupational Safety and Health (NIOSH) and has a silicone polymer skin with defined local tissue thicknesses. Quantitative fit factor evaluations were performed on seven N95 FFR models of various sizes and designs. Donnings were performed with and without a pre-test leak checking method. For each method, four replicate FFR samples of each of the seven models were tested with two donnings per replicate, resulting in a total of 56 tests per donning method. Each fit factor evaluation was comprised of three 86-sec exercises: “Normal Breathing” (NB, 11.2 liters per min (lpm)), “Deep Breathing” (DB, 20.4 lpm), then NB again. A fit factor for each exercise and an overall test fit factor were obtained. Analysis of variance methods were used to identify statistical differences among fit factors (analyzed as logarithms) for different FFR models, exercises, and testing methods. For each FFR model and for each testing method, the NB and DB fit factor data were not significantly different (P > 0.05). Significant differences were seen in the overall exercise fit factor data for the two donning methods among all FFR models (pooled data) and in the overall exercise fit factor data for the two testing methods within certain models. Utilization of the leak checking method improved the rate of obtaining overall exercise fit factors ≥100. The FFR models, which are expected to achieve overall fit factors ≥ 100 on human subjects, achieved overall exercise fit factors ≥ 100 on the StAH. Further research is needed to evaluate the correlation of FFRs fitted on the StAH to FFRs fitted on people. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a file providing detailed information on the advanced head form design and fabrication process.]

Total Inward Leakage Measurement of Particulates for N95 Filtering Facepiece Respirators—A Comparison Study

National Institute for Occupational Safety and Health (NIOSH) certified particulate respirators need to be properly fit tested before use to ensure workers' respiratory protection. However, the effectiveness of American National Standards Institute-/Occupational Safety and Health Administration (ANSI-/OSHA)-accepted fit tests for particulate respirators in predicting actual workplace protection provided to workers is lacking. NIOSH addressed this issue by evaluating the fit of half-mask particulate filtering respirators as a component of a program designed to add total inward leakage (TIL) requirements for all respirators to Title 42 Code of Federal Regulations Part 84. Specifically, NIOSH undertook a validation study to evaluate the reproducibility of the TIL test procedure between two laboratories. A PortaCount® was used to measure the TIL of five N95 model filtering facepiece respirators (FFRs) on test subjects in two different laboratories. Concurrently, filter efficiency for four of the five N95 FFR models was measured using laboratory aerosol as well as polydisperse NaCl aerosol employed for NIOSH particulate respirator certification. Results showed that two N95 models passed the TIL tests at a rate of ~80-85% and ~86-94% in the two laboratories, respectively. However, the TIL passing rate for the other three N95 models was 0-5.7% in both laboratories combined. Good agreement (≥83%) of the TIL data between the two laboratories was obtained. The three models that had relatively lower filter efficiency for laboratory aerosol as well as for NaCl aerosol showed relatively low TIL passing rates in both laboratories. Of the four models tested for penetration, one model with relatively higher efficiency showed a higher passing rate for TIL tests in both laboratories indicating that filter efficiency might influence TIL. Further studies are needed to better understand the implications of the data in the workplace.

Viable Viral Efficiency of N95 and P100 Respirator Filters at Constant and Cyclic Flow

The growing threat of an influenza pandemic presents a unique challenge to healthcare workers, emergency responders, and the civilian population. The Occupational Safety and Health Administration (OSHA) recommends National Institute for Occupational Safety and Health (NIOSH)-approved respirators to provide protection against infectious airborne viruses in various workplace settings. The filtration efficiency of selected NIOSH-approved particulate N95 and P100 filtering facepiece respirators (FFRs) and filter cartridges was investigated against the viable MS2 virus, a non-pathogenic bacteriophage, aerosolized from a liquid suspension. Tests were performed under two cyclic flow conditions (minute volumes of 85 and 135 L/min) and two constant flow rates (85 and 270 L/min). The mean penetrations of viable MS2 through the N95 and P100 FFRs/cartridges were typically less than 2 and 0.03%, respectively, under all flow conditions. All N95 and P100 FFR and cartridge models assessed in this study, therefore, met or exceeded their respective efficiency ratings of 95 and 99.97% against the viable MS2 test aerosol, even under the very high flow conditions. These NIOSH-approved FFRs and particulate respirators equipped with these cartridges can be anticipated to achieve expected levels of protection (consistent with their assigned protection factor) against airborne viral agents, provided that they are properly selected, fitted, worn, and maintained.

Evaluation of Sampling Probes for Fit Testing N95 Filtering Facepiece Respirators

Previous studies have shown a sampling probe bias for measuring fit factors (FFs) in respirator facepieces. This study was conducted to evaluate three sampling probes for fit testing NIOSH-certified N95 filtering facepiece respirators (FFRs). Two phases of fit test experiments were conducted incorporating 'side-by-side' probe mounting: (i) flush probe versus deep probe and (ii) flush probe versus disc probe. Seven test subjects in Phase 1 and six subjects in Phase 2 were fit tested with one to three N95 FFR models for a total of 10 subject/FFR model combinations for each phase. For each experimental condition, induced faceseal leakage (IFSL) through an induced leak was measured using a PORTACOUNT® Plus model 8020A Respirator Fit Tester with a model 8095 N95-Companion™ accessory. For Phase 1, the mean IFSL of all flush probe measurements (3.6%) was significantly greater than (P < 0.05) the mean IFSL of all deep probe measurements (3.3%). For Phase 2, the mean IFSL of all flush probe measurements (8.5%) was not significantly greater than (P > 0.05) the mean IFSL of all disc probe measurements (8.3%). Results indicate that some leak site and subject/FFR model/leak site combination comparisons (flush probe versus deep probe or flush probe versus disc probe) were statistically different (P < 0.05). The overall mean IFSL for subject/FFR model/leak site combinations differed by 14 and 4% for the flush probe versus deep probe and the flush probe versus disc probe, respectively; however, from a practical standpoint, there is little difference between the flush probe tests compared with the deep probe or disc probe tests. Overall, IFSL measured using the flush probe is higher (resulting in a more conservative measure of faceseal leakage) compared with either the deep probe or disc probe. The more conservative results obtained using the flush probe provide support for its common usage for fit testing cup-shaped FFRs in the USA and potential use for fit testing FFRs in Europe.

Evaluation of the Benefit of the User Seal Check on N95 Filtering Facepiece Respirator Fit

The objective of this study was to better understand the benefit of the user seal check step for respirator test subjects in the N95 filtering facepiece respirator donning process. To qualify for the study, subjects were required to pass a standard quantitative fit test on at least one of the three N95 filtering facepiece respirator models: 3M 1860 (cup), 3M 1870 (flat-fold), and Kimberly Clark PFR95-270 (duckbill). Eleven subjects were enrolled and performed a series of abbreviated, quantitative fit tests where they were randomly asked either to perform or not perform a user seal check with 20 different respirator samples of each model. The experimental design included 3 respirator models × 10 subjects × 2 treatment levels with 10 replications. Geometric mean (GM) fit factors and percentages of times a fit factor ≥ 100 was achieved for a donning were compared for each subject with and without the user seal check across all models and for each model. Higher GM fit factors and smaller geometric standard deviations across all models were achieved for 10 of the 11 subjects when performing a user seal check compared with not performing a user seal check. Geometric mean fit factors of 148, 184, and 156, compared with 126, 187, and 115, respectively, were obtained for the 3M 1860, 3M 1870, and Kimberly Clark PFR95-270 models when the user seal check was performed vs. not performed. Differences in the GM fit factors for the 3M 1860 and Kimberly Clark PFR95-270 models were statistically significant (p < 0.05) when performing a user seal check vs. not performing a user seal check. These data suggest that there may be some benefit to performing the user seal check for at least some models during the filtering facepiece respirator donning process for workers who have previously passed a fit test for those respirator models. Additional research is needed with larger groups of subjects and respirator models/types.