Respiratory protection as a function of respirator fitting characteristics and fit-test accuracy

Novel 3D printable powered air purifying respirator for emergency use during PPE shortage of the COVID-19 pandemic: a study protocol and device safety analysis

OBJECTIVES

To design a low-cost 3D printable powered air-purifying respirator (PAPR) that meets National Institute for Occupational Safety and Health (NIOSH) standard for flow rate and Occupational Safety and Health Administration (OSHA) standard for particle filtration for loose-fitting PAPRs and that can be made with a 3D printer and widely available materials.

DESIGN

Detailed description of components, assembly instructions and testing of a novel PAPR design in an academic laboratory following respective protocols. The assembled PAPR must meet NIOSH standards of flow rate, 170 L/min; OSHA fit factor for particle filtration, ≥250 and maintain positive pressure during regular and deep breathing.

MAIN OUTCOME MEASURES

The PAPR design was run through a series of tests: air flow (L/min), particle filtration (quantitative and qualitative) and positive pressure measured inside the helmet (mm Hg).

RESULTS

Flow rate was 443.32 L/min (NIOSH standard: minimum 170 L/min) and overall fit factor for particle filtration was 1362 (OSHA pass level: ≥500), n=1. The device passed qualitative particle filtration, n=2, and measured peak pressure of 6mm Hg (>0 mm Hg indicates positive pressure) in the helmet, n=1.

CONCLUSIONS

The Hygieia PAPR is a low-cost, easily accessible, just-in-time 3D printable PAPR design that meets minimum NIOSH and OSHA standards for flow-rate and particle filtration for loose-fitting PAPR devices to be made and used when industry-made designs are unavailable.

Qualitative fitting characteristics of filtering face-piece respirators on Iranian people

To evaluate the qualitative fitting characteristics of FFRs on Iranian people. 62 participants were fit tested qualitatively by four brands of FFRs, including three imported (A, B, and C) and one domestic (D). The respirators were assigned to the participants randomly based on the Latin Square design (LSD) using the Moldex® Bitrex® Fit Test Kit. R 3.2.5.0 software was used to analyze the data. Among the respirators, A and C respirators had the lowest and highest fit test passing rates with 1.60% and 43.50%, respectively. The majority of the participants had medium face sizes (45.20%) and small and long/narrow shapes (32.20% and 32.30%). There was a significant difference between the passing rate of domestic (D) and imported (C) respirators (p value<0.001). Factors including respirator brand, style, and gender had significant effects on respirator fit (p value<0.01). There was a low fit test passing rate of the studied respirators among participants. Furthermore, 19.40% of the participants fell out of the NIOSH fit test panel. Therefore, it is required to develop a unique bivariate fit test panel and design the respirators based on the Iranian facial dimensions. Meantime, manufacturers need to provide various sizes and styles of the respirators to provide adequate respiratory protection for the users.

Dental services during the COVID-19 pandemic: A tertiary care hospital experience

The Aga Khan University is the largest tertiary care hospital in the biggest metropolis of Pakistan, in this paper six weeks of experience during the COVID‐19 pandemic is shared, we will discuss the measures that were taken to mitigate the spread of COVID‐19 amongst dental health care providers (DHCPS) and provide a neoteric workflow for the provision of safe dental care as dental services move towards normalcy. Furthermore topic such as fit testing, contact tracing, employee health and training are discussed and experience of such measures is shared. It is hoped that till the time new evidence based data is generated these communications may help spread awareness to help setup clinical protocols for other tertiary care settings.

Inward Leakage Variability between Respirator Fit Test Panels - Part I. Deterministic Approach

Inter-panel variability has never been investigated. The objective of this study was to determine the variability between different anthropometric panels used to determine the inward leakage (IL) of N95 filtering facepiece respirators (FFRs) and elastomeric half-mask respirators (EHRs). A total of 144 subjects, who were both experienced and non-experienced N95 FFR users, were recruited. Five N95 FFRs and five N95 EHRs were randomly selected from among those models tested previously in our laboratory. The PortaCount Pro+ (without N95-Companion) was used to measure IL of the ambient particles with a detectable size range of 0.02 to 1 μm. The Occupational Safety and Health Administration standard fit test exercises were used for this study. IL test were performed for each subject using each of the 10 respirators. Each respirator/subject combination was tested in duplicate, resulting in a total 20 IL tests for each subject. Three 35-member panels were randomly selected without replacement from the 144 study subjects stratified by the National Institute for Occupational Safety and Health bivariate panel cell for conducting statistical analyses. The geometric mean (GM) IL values for all 10 studied respirators were not significantly different among the three randomly selected 35-member panels. Passing rate was not significantly different among the three panels for all respirators combined or by each model. This was true for all IL pass/fail levels of 1%, 2%, and 5%. Using 26 or more subjects to pass the IL test, all three panels had consistent passing/failing results for pass/fail levels of 1% and 5%. Some disagreement was observed for the 2% pass/fail level. Inter-panel variability exists, but it is small relative to the other sources of variation in fit testing data. The concern about inter-panel variability and other types of variability can be alleviated by properly selecting: pass/fail level (IL 1-5%); panel size (e.g., 25 or 35); and minimum number of subjects required to pass (e.g., 26 of 35 or 23 of 35).

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.

Real-time fit of a respirator during simulated health care tasks

Fit is an important but difficult-to-predict feature of respirator performance. This study examined a new approach to measuring respirator performance using two continuous direct-reading particle-counting instruments in a simulated health care workplace. A pilot test was conducted with eight experienced health care professionals who passed a traditional quantitative fit test before performing three randomized 10-min health care scenarios (patient assessment [PA], IV treatment [IV], and wound care [WC]). Two TSI Portacount Plus (Model 8020) with N95 Companion (Model 8095) instruments were used to continuously measure 1-sec ambient particle concentrations inside and outside the respirator facepiece. A simulated workplace protection factor (SWPF) was calculated by dividing outside by inside concentrations. Data were log transformed and examined using analysis of variance (ANOVA) between subjects, scenario types, and scenario order. The GM SWPF for the eight subjects, three scenarios per subject, ranged from 172 to 1073 (GSD 1.7 to 3.5) and was significantly different for each subject. A multi-way analysis of variance showed no difference between the three scenario types (PA, IV, WC). There were differences by the order in which scenarios were performed: the third scenario SWPF was significantly different and higher than that of the first and second scenarios. All subjects passed the initial quantitative fit test with a fit factor of at least 100. Five subjects had fit factors greater than 200 and GM scenario SWPFs greater than 400. Three participants with initial fit factors less than 200 had GM scenario SWPFs ranging from 132 to 326. This pilot test demonstrates that it is possible to evaluate instantaneous respirator fit using two quantitative fit test instruments in a simulated health care environment. Results suggest that an initial fit test may be predictive of fit during simulated tasks and that one scenario may be adequate for measuring a simulated workplace protection factor. [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 video for subject D activities overlaid with simulated workplace protection factor data.].

A must for NIOSH: certify fit performance of the half mask particulate respirator

The National Institute for Occupational Safety and Health has proposed to amend the certification rules for half mask air-purifying particulate respirators. The amendment would require the certified respirator to fit a minimum percentage of the intended users. The fail/pass rate for a respirator fitting a worker population has not been part of the certification process for particulate respirators since 1995. The amendment would also add a new requirement for the manufacturer to inform whom the respirator is intended to fit.

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.

Laboratory study to assess causative factors affecting temporal changes in filtering facepiece respirator fit: part I - pilot study

The National Institute for Occupational Safety and Health is conducting a first-of-its-kind study that will assess respirator fit and facial dimension changes as a function of time and improve the scientific basis for decisions on the periodicity of fit testing. A representative sample of 220 subjects wearing filtering-facepiece respirators (FFR) will be evaluated to investigate factors that affect changes in respirator fit over time. The objective of this pilot study (n = 10) was to investigate the variation in fit test data collected in accordance with the study protocol. Inward leakage (IL) and filter penetration were measured for each donned respirator, permitting the calculation of face seal leakage (FSL) and fit factor (FF). The study included only subjects who (a) passed one of the first three fit tests (FF ≥ 100), and (b) demonstrated through a series of nine donnings that they achieved adequate fit (90th percentile FSL was ≤ 0.05). Following the respirator fit tests, 3-D scans of subjects were captured, and height, weight, and 13 traditional anthropometric facial dimensions were measured. The same data were collected 2 and 4 weeks after baseline. The mean change in FSL for the 10 subjects was 0.044% between Visits 1 and 2, and was 0.229% between Visits 1 and 3. Technicians achieved at least moderate reliability for all manual measurements except nose protrusion. Filter penetration was generally less than 0.03%. Geometric mean fit factors were not statistically different among the three visits. The large variability was observed with different respirator samples for the same model, between subjects (inter), and within each subject (intra). Although variability was observed, adequate fit was maintained for all 10 subjects. Pilot scans collected show subject faces remained the same over the 4 weeks. The consistent results during the pilot study indicate that the methods and procedures are appropriate for the 3-year main study. In addition, this baseline fit change data will be compared with future fit changes to determine if the changes are meaningful.

Protecting respiratory health: what should be the constituents of an effective RPE programme?

Although personal respiratory protection is widely recognized as having a lower priority than reduction of any risk at source, respiratory protective equipment (RPE) is a major part of risk management for many employers. We have identified the key elements of what constitutes an effective risk control programme involving RPE, through a 3-fold approach involving (i) a review of the published scientific literature, (ii) exploring the issue through >40 years of research publications from the Institute of Occupational Medicine (IOM) (in which the ergonomics of personal protection equipment has been a significant thread), and (iii) a series of interviews and discussions with IOM and Health and Safety Executive staff with experience in the testing, prescription, or use of RPE. We have used the findings to formulate a series of recommendations for the constituents of an effective RPE programme. The role of management is paramount in recognizing the need for and providing appropriate RPE, which is both technically and ergonomically effective. Only then does any focus on the role of the employee, in wearing the RPE correctly at the appropriate times, becomes viable.

Variability of Real-World Hearing Protector Attenuation Measurements

The attenuation provided by a hearing protection device (HPD) in the field is usually estimated by applying a derating factor to the laboratory-determined noise reduction rating (NRR) of the HPD. However, attenuation is highly dependent on individual-specific HPD fit. Prediction of an individual's attenuation depends on the accuracy of the measurement system and the variability of attenuation over time (e.g. after HPD refitting). Variability in attenuation and attenuation test systems has not been adequately characterized to allow for such an assessment. This study compared attenuation measurements made with two systems, Real-Ear-at-Threshold (REAT) and Microphone-in-Real-Ear (MIRE), on 20 workers using two earplugs (foam and custom-molded). Workers' perceptions of the earplugs were also evaluated. Individuals' attenuation results were summarized as personal attenuation ratings (PARs, similar to NRRs). Variability in PARs from between-subject, within-subject and within-day (i.e. repeated tests on a subject without earplug refitting) differences was assessed and used to present the lower confidence limit, or uncertainty factor (UF), of an average individual's attenuation. The custom-molded earplug PARs achieved a higher mean percentage of labeled attenuation than did the foam earplug with both test systems. The custom-molded earplugs also had higher overall acceptance among workers. MIRE PAR levels were lower than REAT levels for both earplugs, but the relationship between the two test systems was highly variable. The MIRE system had lower within-day variability than the REAT system. One individual's MIRE results were highly influential; removal of these results greatly reduced the UF for the custom-molded earplug/MIRE combination. UFs ranged from 8.8 to 13.5 dB. These findings highlight the importance of evaluating variability in individual-specific protection results for personal protective equipment like HPDs, rather than relying on single measurements.

Errors associated with three methods of assessing respirator fit

Three fit test methods (Bitrex, saccharin, and TSI PortaCount Plus with the N95-Companion) were evaluated for their ability to identify wearers of respirators that do not provide adequate protection during a simulated workplace test. Thirty models of NIOSH-certified N95 half-facepiece respirators (15 filtering-facepiece models and 15 elastomeric models) were tested by a panel of 25 subjects using each of the three fit testing methods. Fit testing results were compared to 5th percentiles of simulated workplace protection factors. Alpha errors (the chance of failing a fit test in error) for all 30 respirators were 71% for the Bitrex method, 68% for the saccharin method, and 40% for the Companion method. Beta errors (the chance of passing a fit test in error) for all 30 respirator models combined were 8% for the Bitrex method, 8% for the saccharin method, and 9% for the Companion method. The three fit test methods had different error rates when assessed with filtering facepieces and when assessed with elastomeric respirators. For example, beta errors for the three fit test methods assessed with the 15 filtering facepiece respirators were < or = 5% but ranged from 14% to 21% when assessed with the 15 elastomeric respirators. To predict what happens in a realistic fit testing program, the data were also used to estimate the alpha and beta errors for a simulated respiratory protection program in which a wearer is given up to three trials with one respirator model to pass a fit test before moving onto another model. A subject passing with any of the three methods was considered to have passed the fit test program. The alpha and beta errors for the fit testing in this simulated respiratory protection program were 29% and 19%, respectively. Thus, it is estimated, under the conditions of the simulation, that roughly one in three respirator wearers receiving the expected reduction in exposure (with a particular model) will fail to pass (with that particular model), and that roughly one in five wearers receiving less reduction in exposure than expected will pass the fit testing program in error.

Reducing respirator fit test errors: a multi-donning approach

As a continuation of recent studies to assess the accuracy of existing fit test methods, a multi-donning approach to fit testing is presented. As an example of that approach, a multi-donning quantitative fit test for filtering-facepiece respirators is presented and analyzed by comparing its error rates with those of the single-donning approach of current fit test methods. That analysis indicates the multi-donning fit test has the potential to reduce both the alpha error and the beta error to half that of single-donning fit tests. The alpha error is the error of failing a respirator that should pass; the beta error is the error of passing a respirator that should fail. Lowering fit test error rates for filtering-facepiece respirators is important because fit testing is an essential means of helping assure that an individual has selected an adequately fitting respirator. To reduce the alpha and beta error inherent in current fit test methods, the proposed fit test for filtering-facepiece respirators incorporates five donnings of the facepiece, unlike the single donning of existing fit test methods. The analysis presented here indicates that the multiple-donning approach reduces the element of chance in the fit test result and thereby increases the consistency and accuracy of the fit tests. The time to conduct the multi-donning test can approximate the time for current, single-donning tests by shortening the time the respirator is worn after each donning to about 10 sec. And, unlike current fit tests for filtering-facepieces that measure only faceseal leakage, the example multiple-donning fit test considered here is based on a measurement of total leakage (faceseal plus filter). Utilizing total respirator leakage can result in simpler quantitative fit test instrumentation and a fit test that is more relevant to the workplace. Further trials with human subjects are recommended in order to validate the proposed multi-donning approach.

Fitting characteristics of eighteen N95 filtering-facepiece respirators

Four performance measures were used to evaluate the fitting characteristics of 18 models of N95 filtering-facepiece respirators: (1) the 5th percentile simulated workplace protection factor (SWPF) value, (2) the shift average SWPF value, (3) the h-value, and (4) the assignment error. The effect of fit-testing on the level of protection provided by the respirators was also evaluated. The respirators were tested on a panel of 25 subjects with various face sizes. Simulated workplace protection factor values, determined from six total penetration (face-seal leakage plus filter penetration) tests with re-donning between each test, were used to indicate respirator performance. Five fit-tests were used: Bitrex, saccharin, generated aerosol corrected for filter penetration, PortaCount Plus corrected for filter penetration, and the PortaCount Plus with the N95-Companion accessory. Without fit-testing, the 5th percentile SWPF for all models combined was 2.9 with individual model values ranging from 1.3 to 48.0. Passing a fit-test generally resulted in an increase in protection. In addition, the h-value of each respirator was computed. The h-value has been determined to be the population fraction of individuals who will obtain an adequate level of protection (i.e., SWPF >/=10, which is the expected level of protection for half-facepiece respirators) when a respirator is selected and donned (including a user seal check) in accordance with the manufacturer's instructions without fit-testing. The h-value for all models combined was 0.74 (i.e., 74% of all donnings resulted in an adequate level of protection), with individual model h-values ranging from 0.31 to 0.99. Only three models had h-values above 0.95. Higher SWPF values were achieved by excluding SWPF values determined for test subject/respirator combinations that failed a fit-test. The improvement was greatest for respirator models with lower h-values. Using the concepts of shift average and assignment error to measure respirator performance yielded similar results. The highest level of protection was provided by passing a fit-test with a respirator having good fitting characteristics.