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.

Impact of multiple consecutive donnings on filtering facepiece respirator fit.

BACKGROUND: A concern with reuse of National Institute for Occupational Safety and Health-certified N95 filtering facepiece respirators (FFRs) is that multiple donnings could stress FFR components, impairing fit. This study investigated the impact of multiple donnings on the facepiece fit of 6 N95 FFR models using a group of 10 experienced test subjects per model. METHODS: The TSI PORTACOUNT Plus and N95 Companion accessory were used for all tests. After qualifying by passing a standard Occupational Safety and Health Administration fit test, subjects performed up to 20 consecutive tests on an individual FFR sample using a modified protocol. Regression analyses were performed for the percentage of donnings resulting in fit factors (FFs) ≥100 for all 6 FFR models combined. RESULTS: Regression analyses showed statistical significance for donning groups 1-10, 1-15, and 1-20. The mean percentage of donnings with an FF ≥100 was 81%-93% for donning group 1-5, but dropped to 53%-75% for donning group 16-20. CONCLUSIONS: Our results show that multiple donnings had a model-dependent impact on fit for the 6 N95 models evaluated. The data suggest that 5 consecutive donnings can be performed before FFs consistently drop below 100.

Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.

The objective of this study was to determine if ultraviolet germicidal irradiation (UVGI), moist heat incubation (MHI), or microwave-generated steam (MGS) decontamination affects the fitting characteristics, odor, comfort, or donning ease of six N95 filtering facepiece respirator (FFR) models. For each model, 10 experienced test subjects qualified for the study by passing a standard OSHA quantitative fit test. Once qualified, each subject performed a series of fit tests to assess respirator fit and completed surveys to evaluate odor, comfort, and donning ease with FFRs that were not decontaminated (controls) and with FFRs of the same model that had been decontaminated. Respirator fit was quantitatively measured using a multidonning protocol with the TSI PORTACOUNT Plus and the N95 Companion accessory (designed to count only particles resulting from face to face-seal leakage). Participants' subjective appraisals of the respirator's odor, comfort, and donning ease were captured using a visual analog scale survey. Wilcoxon signed rank tests compared median values for fit, odor, comfort, and donning ease for each FFR and decontamination method against their respective controls for a given model. Two of the six FFRs demonstrated a statistically significant reduction (p < 0.05) in fit after MHI decontamination. However, for these two FFR models, post-decontamination mean fit factors were still ≥ 100. One of the other FFRs demonstrated a relatively small though statistically significant increase (p < 0.05) in median odor response after MHI decontamination. These data suggest that FFR users with characteristics similar to those in this study population would be unlikely to experience a clinically meaningful reduction in fit, increase in odor, increase in discomfort, or increased difficulty in donning with the six FFRs included in this study after UVGI, MHI, or MGS decontamination. Further research is needed before decontamination of N95 FFRs for purposes of reuse can be recommended.

Evaluation of five decontamination methods for filtering facepiece respirators.

Concerns have been raised regarding the availability of National Institute for Occupational Safety and Health (NIOSH)-certified N95 filtering facepiece respirators (FFRs) during an influenza pandemic. One possible strategy to mitigate a respirator shortage is to reuse FFRs following a biological decontamination process to render infectious material on the FFR inactive. However, little data exist on the effects of decontamination methods on respirator integrity and performance. This study evaluated five decontamination methods [ultraviolet germicidal irradiation (UVGI), ethylene oxide, vaporized hydrogen peroxide (VHP), microwave oven irradiation, and bleach] using nine models of NIOSH-certified respirators (three models each of N95 FFRs, surgical N95 respirators, and P100 FFRs) to determine which methods should be considered for future research studies. Following treatment by each decontamination method, the FFRs were evaluated for changes in physical appearance, odor, and laboratory performance (filter aerosol penetration and filter airflow resistance). Additional experiments (dry heat laboratory oven exposures, off-gassing, and FFR hydrophobicity) were subsequently conducted to better understand material properties and possible health risks to the respirator user following decontamination. However, this study did not assess the efficiency of the decontamination methods to inactivate viable microorganisms. Microwave oven irradiation melted samples from two FFR models. The remainder of the FFR samples that had been decontaminated had expected levels of filter aerosol penetration and filter airflow resistance. The scent of bleach remained noticeable following overnight drying and low levels of chlorine gas were found to off-gas from bleach-decontaminated FFRs when rehydrated with deionized water. UVGI, ethylene oxide (EtO), and VHP were found to be the most promising decontamination methods; however, concerns remain about the throughput capabilities for EtO and VHP. Further research is needed before any specific decontamination methods can be recommended.

Evaluation of the filtration performance of 21 N95 filtering face piece respirators after prolonged storage.

BACKGROUND: Organizations are stockpiling respirators to prepare for an influenza pandemic. To understand better the effects of prolonged storage, this investigation evaluated the filtration efficiency of 21 different models of National Institute for Occupational Safety and Health (NIOSH)-certified disposable N95 filtering face piece respirators. These respirators had been stored in their original packaging for a period of at least 6 years in research laboratories and dry warehouse facilities, ranging in temperature between 15 degrees C and 32 degrees C and relative humidity between 20% and 80%. METHODS: Filter penetration was measured using an abbreviated version of the NIOSH respirator certification test incorporating a polydisperse sodium chloride aerosol at 85 L/min. RESULTS: Of the 21 respirator models tested, 19 models had both average penetration results of less than 5%. Mean initial penetration values ranged from 0.39% to 5.83%, whereas mean maximum penetration values ranged from 0.95% to 5.83%. There did not appear to be any correlation between the length of storage and failure to pass the filtration test. CONCLUSION: Results indicate that most N95 filtering face piece respirators stored for up to 10 years at warehouse conditions will likely have expected levels of filtration performance and that the degree of filtration efficiency degradation is likely model specific.