Z. Zhuang, R. Shaffer, NIOSH, Pittsburgh, PA; B. Bradtmiller, Anthrotech, Yellow Springs, OH.
The respirator fit test panels currently used are 25-subject panels, developed by Los Alamos National Laboratory (LANL). The LANL panels are based on data from the 1967 and 1968 anthropometric surveys of U.S. Air Force men and women. Previous work has shown that military data do not represent the great diversity in face size and shape seen in today’s civilian populations. This paper presents the development of a new respirator fit test panel representative of the current U.S. civilian workers using principal component analysis (PCA). A database containing 19 neck, head, and face measurements for 3,997 respirator users was created in 2003 from a nationwide anthropometric survey. Correlation analyses were conducted to identify dimensions that can be predicted well by other dimensions. Dimensions that have been shown to be associated with respirator fit were also identified. A set of 10 face dimensions was then selected for PCA. A respirator fit test panel was developed using the scores from the first two principal components obtained from the 10 face dimensions (age- and race-adjusted). The 10 face dimensions on which the panel is based have good correlations with, and can predict, the 9 dimensions that were excluded in the model. The new PCA panel is expected to accommodate more than 95% of the current U.S. civilian work force and may be appropriate for testing half-mask and full-facepiece respirators. Interpretation of the PCA loadings and scores provided insight into the relationships between key facial dimensions. These data suggest that new sizing systems that incorporate both the size and shape of the face may be appropriate for use with the new PCA panel. A software program was also developed to assist in the measurement of the 10 dimensions and to calculate principal component scores.
R. Roberge, Z. Zhuang, L. Stein, NIOSH, Pittsburgh, PA.
The current epidemic of overweight and obesity in the U.S. and other developed nations has reached epidemic proportions, but little work has been done addressing the impact of increasing body weight upon personal protective equipment (PPE). Utilizing the National Personal Protective Technology Laboratory (NPPTL) respirator fit test panel, this study was undertaken to investigate any possible effect of overweight or obese states on facial dimensions, and to compare prior anthropometric surveys for the purpose of analyzing study population differences that might affect facial dimensions. The data base consisted of three previously published anthropometric studies (two military, one civilian) that were analyzed for homogeneity of study populations and for the impact of variables thought to influence facial dimensions (i.e., age, gender, race/ethnicity, body mass index). The mean age, BMI, and face width were greater for the civilian survey subjects than either of the military surveys (p < .01 for each variable). Face width and face length were associated with BMI in both genders of civilian subjects (p < .01), as was the interaction of race/ethnicity, age, and BMI for civilian females (p = 0.04) and the interaction of race/ethnicity and BMI for civilian males (p = 0.02). Increasing BMI impacted face width more than face length (p < .05). As the epidemic of overweight and obesity continues, associated increases in facial dimensions of the civilian work force should be anticipated and considered by respirator stakeholders. Researchers developing respirator fit test panels should evaluate BMI, as it may offer a clue to increasing facial dimensions. Further research will be required to determine how much increase in body weight signals the need for repeat respirator fit testing and to ascertain if fit test data from more physically fit subjects are applicable to overweight or obese subjects.
R. McKay, J. Bradley, University of Cincinnati, Cincinnati, OH.
This study investigated three new quantitative fit testing protocols designed for use with the TSI PortaCount. Each of the protocols was designed to shorten the time required to perform an OSHA 8-exercise quantitative fit test with results compared to the acceptance criteria established by ANSI Z88.10. A total of 30 subjects conducted 140 fit tests with a variety of good and poor fitting half and full facepiece respirators. Two of the protocols in this study (protocols #2 and #3) utilized a shortened in-facepiece sampling time to reduce the length of each exercise maneuver from 60 to 40 seconds. This was achieved by reducing the in-facepiece sampling time while keeping ambient sample and purge times unchanged. Test sensitivity for protocol #2 was 0.97 when the reference method pass/fail criterion was set to either 100 or 500. This exceeds the ANSI recommendation for accepting a new fit test method. Protocol #3 used the same exercise time as protocol #2; however, the total test time was further reduced by eliminating the first two exercise maneuvers while using a more stringent pass fail criterion. Test sensitivity for protocol #3 was 1.00 when the reference pass/fail criterion was set to either 100 or 500. All three of the new test protocols were highly correlated with the reference fit test method. Correlation coefficients for protocols #1, #2, and #3 were 0.956, 0.988, and 0.982, respectively. This study demonstrated that reducing the exercise time with the TSI PortaCount had little effect on the ability of this instrumentation to identify poorly fitting respirators. In addition, eliminating the first two exercise maneuvers from the 1998 OSHA 8-exercise protocol in conjunction with doubling of the pass/fail criterion not only provides a significantly faster fit test protocol, but provides a more conservative fit test for quantitative respirator fit testing.
L. Steenweg, S. van der Gijp, B. Nijboer, TNO Defence, Security & Safety, Rijswijk, The Netherlands.
For testing and certification of gas masks, a laboratory method is used to measure the level of protection on human beings, although it is known that in actual use this level of protection can be much lower than measured in the laboratory. TNO Defense, Safety & Security has developed a method that enables us to measure online the level of protection that is offered by a gas mask. The pressure inside the mask, a value for the breathing flow, can be measured. This development was done in close cooperation with DSTL (UK) and FFI (Norway). Various masks, widely used in industry were evaluated with respect to the level of protection while the wearers were performing a representative task. In the presentation, the test device will be described as well as the results that are obtained.
J. Bidwell, L. Janssen, 3M, St. Paul, MN.
The purpose of this study was to determine workplace performance of a full-facepiece respirator with P100 filters by measuring workplace protection factors (WPFs). The 4-day study was conducted in a lead refining plant. Prior to sampling, 19 workers were quantitatively fit tested with NIOSH-approved full-facepiece respirators having P100 filters following the Portacount protocol specified in 29 CFR 1910.134. Three to four pairs of air samples per day were collected from each worker. Tasks included handling lead ingots, skimming dross, operating a blast furnace, sweeping and shoveling, and driving fork trucks. Trained observers assisted in the study to ensure sample validity. Post-study, outside samples were analyzed by inductively coupled plasma spectroscopy, while inside samples were analyzed via proton-induced X-ray emission analysis. Lead was consistently found in the outside sample laboratory results, although it was nondetected in all but one of the inside samples. The single measurable inside sample yielded a WPF of 297. The fifth percentile WPF of approximately 6000 was calculated by dividing each of the outside samples by the detection limit, then performing a rank and percentile function. The WPFs for this respirator model based on this study exceed the APF of 50 for this respirator class as used by the National Institute for Occupational Safety & Health and proposed by the Occupational Safety & Health Administration. These results support the APF of 50 for this respirator and indicate the respirator provided adequate protection as used in this study.
L. Janssen, N. Anderson, R. Weber, 3M Company, St. Paul, MN; P. Cassidy, Exponent Failure Analysis Associates, Natick, MA; T. Nelson, NIHS, Inc., Ardentown, DE.
Recent studies and much debate have focused on quantifying the airflow requirements of respirator users, particularly under conditions of very high to maximal work rates. It is often assumed that respirators and their components must be tested at flow rates that closely match the maximal airflow measurements to assure protection to users. This overly simplified assumption ignores the differences between laboratory tests and the workplace conditions in which respirators are used. Although respirators and their components could be designed to comply with any necessary airflow requirement, objective data do not suggest that an increase in testing flow rates would benefit respirator users. This paper suggests appropriate use of airflow measurements in setting respirator performance criteria and evaluating user protection. There is no indication that respirators meeting current U.S. approval criteria or substantially similar tests need performance enhancement to provide acceptable protection.
A. Viner, S. Kalatoor, L. Janssen, 3M Occupational Health & Environmental Safety Division, St. Paul, MN.
Given the cyclical nature of human breathing cycles, instantaneous flow rates can far exceed the minute volume average breathing rate. For example, under NFPA test conditions (30 breaths/min, 103 ± 3 L/min average flow), which simulate heavy/extra heavy work, the peak flow exceeds 320 L/min for approximately 0.1 s of each inhalation. For comparison, the NIOSH protocol for testing filtering facepiece respirators specifies a constant flow rate of 85 L/min. A study was conducted to compare initial penetration through respirators (two models of N95 and one N100) under a continuous flow condition (85 L/min) and cyclic flow condition. A programmable, linear-drive, piston-type breathing machine was programmed to operate under NFPA sinusoidal breathing conditions. The breathing machine was attached to the downstream side of the sample holder of an Automated Filter Tester (AFT). The AFT was configured to run with a NaCl aerosol conforming to NIOSH 42 CFR 84 size distribution requirements. A condensation particle counter was used to measure particle concentrations downstream of the respirator with a time resolution of 0.1 s. The cyclic nature of the flow was clearly reflected in the real-time penetration data. For one model of N95 respirator, the average of the minimum penetrations during each cycle was 0.54% and the average peak penetration was 0.85%. For the other N95 respirator, the average minimum was 0.71% and the average peak value was 1.1%. Initial penetration through the N100 respirator was so low that it was difficult to recognize the cyclic flow pattern. Average penetration was less than 0.001%. The penetrations under cyclic flow conditions are comparable to the penetrations achieved with a constant flow of 85 L/min. In summary, an initial penetration measured under NIOSH test conditions is a reasonable predictor of initial penetration measured under cyclic flow conditions that simulate heavy work.
J. Huberty, L. Janssen, J. Bidwell, 3M Company, St. Paul, MN.
Recent laboratory measurements have renewed interest in the potential degrading effects of oily aerosols on electret filter media. In this study, European CEN approved P1 and P2 filtering face-piece respirators and filters were exposed to a paraffin oil aerosol in a tool cutting operation over 3 consecutive days to investigate the effects of time and loading on filtration performance. Overall mass based penetrations for the workplace aerosol were calculated. In addition, laboratory filter penetration tests were conducted on the samples each day prior to workplace exposure. The laboratory filter measurements were conducted against a paraffin oil aerosol generated near the most penetrating particle size. Although the laboratory tests show increasing penetrations with time and loading, the filters and respirators performed very well against the workplace aerosol.
C. Manning, G. Nelson, Assay Technology, Pleasanton, CA.
The basis for NIOSH certification of air-purifying respirator cartridges, 42CFR84, includes an equilibrated carbon tetrachloride challenge test following a preliminary high-humidity preconditioning period. Although this test is meant to predict cartridge performance against all organic vapors, the adsorption and retention of carbon tetrachloride by activated carbon is particularly sensitive to moisture adsorbed. Small laboratory variations in temperature and humidity during preconditioning stage lead to large differences in water uptake during the preconditioning cycle. This, in turn, results in large differences in the cartridge service life even when the same respirator cartridge is tested under apparently identical conditions. This investigation studied the effect of temperature and humidity variations on the service lives of organic vapor respirator cartridges. Results demonstrated that variations on the order of ± 50% in service life can be induced by the temperature and humidity tolerances allowed under the current NIOSH test method. The investigators suggest that the precision of organic vapor certification tests could be improved either by tightening the temperature and humidity variations allowed during testing or by a substitution of a different challenge chemical (e.g., cyclohexane) that is not so sensitive to small variations in temperature and humidity.
Posted May 30, 2006