Warren R. Myers

REVIEW OF RESPIRATOR PERFORMANCE TESTING IN THE WORKPLACE: ISSUES AND CONCERNS

Performance capability of respirators has traditionally been evaluated by testing components of the respirator (e.g., filter efficiency), facepiece fit, total inward leakage, or some other measure of performance evaluated under laboratory conditions. In recent years, increased emphasis has been placed on development of test methods suitable for evaluating respirator performance in the workplace. The goal of such testing is to evaluate the level of protection provided by respirators in the work environment. The AIHA Respiratory Protection Committee believes that workplace testing of respirators has the potential to be an excellent tool for increasing knowledge about the effectiveness of respiratory protection. However, a number of technical issues remain to be addressed before optimal test protocols and data analysis methods can be defined. The progress made to date in workplace testing will be reviewed, and broader discussion about key elements that must be considered when developing guidelines for testing respirators in the workplace will be initiated.

Comparison of Five Methods for Fit-Testing N95 Filtering-Facepiece Respirators

Five fit-testing methods (Bitrex, ambient aerosol condensation nuclei counter using the TSI PortaCount Plus, saccharin, modified ambient aerosol condensation nuclei counter using the TSI PortaCount Plus with the N95-Companion, and generated aerosol using corn oil) were evaluated for their ability to identify poorly fitting N95 filtering-facepiece respirators. Eighteen models of NIOSH-certified, N95 filtering-facepiece respirators were tested by a panel of 25 subjects using each fit-testing method. The penetration of the corn oil and the ambient aerosols through the filter media of each respirator was measured in order to adjust the corresponding generated and ambient aerosol overall fit factors, reflecting only face-seal leakage. Fit-testing results were compared to 5th percentiles of simulated workplace protection factors. Beta errors (the chance of passing a fit-test in error) ranged from 3 percent to 11 percent. Alpha errors (the chance of failing a fit-test in error) ranged from 51 percent to 84 percent. The ambient aerosol using the TSI PortaCount Plus and the generated aerosol methods identified poorly fitting respirators better than the saccharin, the Companion, and Bitrex methods. These errors rates should be considered when selecting a fit-testing method for fitting N95 filtering-facepieces. When both types of errors were combined as an assignment error, the ambient aerosol method using the TSI PortaCount Plus had the lowest percentage of wearers being assigned a poor-fitting respirator.

Field Performance Measurements of Half-Facepiece Respirators—Foundry Operations

A series of field studies was conducted to measure workplace protection factors (WPF) provided by elastomeric and disposable half-facepiece respirators against different particulate contaminants. The research protocol developed for the study has been described in a previous article. This article presents results from dust and fume exposures at three foundries. The major components of the airborne exposures in these foundries were zinc, lead, and silicon. The major components of the in-facepiece samples were zinc, chlorine, and lead. Significant differences were observed in ambient zinc and lead concentration levels among foundries; however, no significant difference was observed in the in-facepiece concentrations of these elements among foundries. Respirator performance varied within each foundry, but there was no difference in performance when pooling all foundry data. The 5th, 10th and 50th percentile estimates for the pooled foundry and respirator WPF data were about 9, 16, and 114 respectively. The infacepiece concentration data clearly indicate that dust-fume-mist (DFM) class half-facepiece respirators, when conscientiously used, worn, and maintained, in conjunction with other existing controls in these foundries, provided effective worker protection.

Correlation Between Quantitative Fit Factors and Workplace Protection Factors Measured in Actual Workplace Environments at a Steel Foundry

Past studies have found little or no correlation between workplace protection factors (WPFs) and quantitative fit factors (FFs). This study investigated the effect of good- and poor-fitting half-facepiece, air-purifying respirators on protection in actual workplace environments at a steel foundry and the correlation between WPFs and FFs. Fifteen burners and welders, who wore respirators voluntarily, and chippers participated in this study. Each subject was fit-tested with two respirator models each with three sizes, for a total of six fit-tests. Models and sizes were assigned this way to provide a wide range of FFs among study participants. Each worker donned the respirator twice per day (at the beginning of the shift and following the lunch break) for 2 days. Quantitative FFs were first obtained for each donning using the PortaCount Plus trade mark in a separate room. Without redonning the respirators, workers performed normal work for 1 to 2 hours, and WPFs were measured by collecting ambient and in-facepiece samples simultaneously. A second fit-test was conducted without disturbing the respirator. FFs were obtained by averaging the results from the first and second fit-tests. The resulting FFs had a geometric mean (GM) of 400 (range=10-6010) and a geometric standard deviation (GSD) of 6.1. Of the 55 valid donnings, 43 were good fitting (FFs> or =100) and 12 were poor fitting (FFs<100). The WPFs had a GM of 920 (range=13-230,000) and a GSD of 17.8. The WPFs were found to be significantly correlated with the FFs (R(2)=.55 and p-value=.0001). Therefore, FF was shown to be a meaningful indicator of respirator performance in actual workplace environments.

Field Performance Measurements of Half-Facepiece Respirators: Steel Mill Operations

Ambient and in-facepiece samples to evaluate the protection provided by negative-pressure, half-facepiece respirators were collected on workers in different areas of a steel mill including a sinter plant and a basic oxygen process shop. Protection was assessed by workplace protection factors (WPF). All the in-facepiece concentrations were dramatically less than the corresponding ambient concentration levels or permissible exposure limits. The geometric mean (GM) ambient and in-facepiece concentrations of iron were found to vary among tasks. Significant differences were also found to occur between the GM ambient exposure levels in which some of the respirators were used. Significant differences in respirator performance as measured by WPF or in-facepiece iron concentration were observed among different brands of respirators. For all job classifications and at all levels of airborne exposure, the fifth percentile estimates for the WPF distributions for each brand of respirator were all greater than 20.

Field Performance Measurements of Half-Facepiece Respirators—Study Protocol

This article presents the research protocol used for a series of field studies that were conducted to measure workplace protection factors (WPF) for elastomeric and disposable half-facepiece respirators against particulate contaminants. The protocol was used for studies at three brass foundries, an aircraft painting operation, and a steel mill sinter plant. Particulate contaminants evaluated in these industries-operations included various metal dusts and fumes and paint overspray that included metallic pigment. In this article findings are reported on aspects of the sampling and analytical methodology that were employed for the first time in these studies. These include (1) collection of WPF samples during different parts of the shift, (2) collection of respirable dust samples, (3) washing of sample cassettes, and (4) use of proton induced X-ray emission analysis. Workplace protection factor results measured after the respirator was worn for several hours were generally higher than those measured when it ...

Field performance measurements of half-facepiece respirators : paint spraying operations

This article presents the results of a workplace protection factor (WPF) study for half-facepiece respirators conducted in an aircraft paint-spraying operation. The major elements of the paint overspray collected with ambient samples were titanium, strontium, chromium, and silicon. The major elements collected on the in-facepiece samples were chlorine and silicon. The geometric mean (GM) ambient concentrations of chromium and titanium varied significantly among painting locations and paint types. There was a significant difference in GM in-facepiece concentrations of titanium among painting locations. However, no significant difference in GM in-facepiece concentrations of chromium by location was found. In both ambient and in-facepiece samples the amounts of chromium and strontium were highly correlated as expected. In ambient samples total airborne mass was highly correlated with levels of chromium and titanium when primer and top coat were applied, respectively. No difference in respirator performance, ...

Diesel particulate matter exposure to railroad train crews.

Exposure assessments were conducted aboard diesel locomotives. Results were evaluated to determine variables that affect exposure to DPM (diesel particulate matter) and to assess use of EC (elemental carbon) and OC (organic carbon) as surrogates for DPM. National Institute for Occupational Safety and Health Method 5040 was used for collection and analysis of samples in locomotives and in nonrailroad settings. The level of EC, but not OC, in locomotives was found to be significantly affected by position of exhaust stacks and windows. EC ranged from < 1 to 45 micrograms/m3 with a geometric mean (GM) of 3.7 micrograms/m3 and OC ranged from 4 to 4570 micrograms/m3 with a GM of 36.3 micrograms/m3. Background measurements of EC ranged from < 1 to 8 micrograms/m3 and OC levels were 4 to 84 micrograms/m3. This study confirms that train crew exposure to DPM is much lower than exposures for miners, is comparable to background urban exposures, and is lower than but comparable to exposures for truck drivers. It also indicates that EC levels are highly predictive of diesel exhaust exposure whereas OC levels are not, and that open windows and exhaust stack(s) in front of the locomotive cab have a significant effect on EC.

Effectiveness of Fit Check Methods on Half Mask Respirators

Abstract Studies were conducted to evaluate whether a positive/negative (+/-) fit check was an effective aid in helping users of respiratory protective equipment (RPE) achieve a good fit when donning the RPE. Two types of half-facepiece RPE were used in the studies: the disposable, filtering facepiece and the elastomeric facepiece. Three models of disposable, filtering facepiece and one model of dual-cartridge, elastomeric facepiece were evaluated. A population of 64 inexperienced users of RPE was randomly divided into two equal groups. One group was trained to don the RPE using the +/- fit check as an aid, while the second group was trained to don the RPE without conducting a +/- fit check. The number of successful RPE donnings achieved in the group using the fit check was compared with the number of successful RPE donnings achieved in the group not using a fit check. The data obtained from this experiment suggested that, in general, fewer unsuccessful donnings and more consistent donnings were obtained ...

Field performance measurements of half-facepiece respirators: developing probability estimates to evaluate the adequacy of an APF of 10.

To evaluate the protection provided by negative-pressure, half-facepiece respirators, ambient and in-facepiece samples were collected on workers in foundry, aircraft-painting, and steel-manufacturing operations. Protection was assessed by workplace protection factors (WPF). The appropriateness of the assigned protection factor (APF) for half-facepiece respirators was evaluated with a new approach using the WPF data from these and other studies previously published. The new approach utilizes binomial statistics based on the number of successes (no overexposure) and failures (overexposure) and is illustrated with a graphical representation of WPF data. With this consideration of the data, the probability of overexposure occurring during a wearing period for workers wearing the half-facepiece respirators represented by the studies referenced here was 0.5%, with a 95% confidence interval of 0.01 to 2.7%. If 50% in-facepiece sampling errors are considered, the probability of overexposure was 2.9%, with a 95% confidence interval of 1.1 to 6.3%. The authors believe the current APF of 10 for half-facepiece respirators is appropriate.