Parameters that Bias the Measurement of Airborne Concentration Within a Respirator

Myers, Walter Dean; Allender, Joan; Plummer, Ralph W.; Stobbe, Terrence J.

doi:10.1080/15298668691389423

Cited by 30 publications

(13 citation statements)

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“…Higher sampling rate also reduces respirator purge time and significantly declines potential sampling bias especially for nonhomogeneous particles. (19,20) CONCLUSIONS T he N95 elastomeric and filtering facepiece respirators tested in the study provided expected level of respiratory protection for workers in agricultural farms. The 5th percentiles for the ER and FFR were higher than the APF of 10 and varied from 28 to 250 for ER, and from 16 to 223 for FFR.…”

Section: Resultsmentioning

confidence: 95%

Effect of Particle Size on Respiratory Protection Provided by Two Types of N95 Respirators Used in Agricultural Settings

Cho

Jones

et al. 2010

Journal of Occupational and Environmental Hygiene

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This study compared size-selective workplace protection factors (WPFs) of an N95 elastomeric respirator (ER) and an N95 filtering facepiece respirator (FFR) in agricultural environments. Twenty-five healthy farm workers ranging in age from 20 to 30 years voluntarily participated in this study. Altogether, eight farms were included representing three different types: two horse farms, three pig barns, and three grain handling sites. Subjects wore the ER and FFR while performing their daily activities, such as spreading hay, feeding livestock, and shoveling. Aerosol concentrations in an optical particle size range of 0.7-10 μm were determined simultaneously inside and outside the respirator during the first and last 15 min of a 60-min experiment. For every subject, size-selective WPFs were calculated in 1-min intervals and averaged over 30 min. For the ER, geometric mean WPFs were 172, 321, 1013, 2097, and 2784 for particle diameters of 0.7-1.0, 1.0-2.0, 2.0-3.0, 3.0-5.0, and 5.0-10.0 μm, respectively. Corresponding values for the FFR were 67, 124, 312, 909, and 2089. The 5th percentiles for the ER and FFR were higher than the assigned protection factor of 10 and varied from 28 to 250 and from 16 to 223, respectively. Results show that the N95 ER and FFR tested in the study provided an expected level of protection for workers on agricultural farms against particles ranging from 0.7 to 10 μm. WPFs for the ER were higher than the FFR for all particle size ranges. WPFs for both respirator types increased with increasing particle size.

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Section: Resultsmentioning

confidence: 95%

Effect of Particle Size on Respiratory Protection Provided by Two Types of N95 Respirators Used in Agricultural Settings

Cho

Jones

et al. 2010

Journal of Occupational and Environmental Hygiene

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“…Sampling errors of Ϫ99 to ϩ98% have been demonstrated for in-facepiece aerosol sampling. (14) Particle loss in the needle or tubing used to induce the leak, leak geometry, and leak location appear to contribute to these biases. (9,14,16) Further, it has not been shown that any fixed leak location or geometry adequately represents leaks that occur during actual respirator use.…”

Section: Discussionmentioning

confidence: 95%

“…Potential concerns associated with fixed leaks include particle losses in the needle or tubing used to induce the leak, nonrepresentative leak geometry, and aerosol sampling bias associated with the choice of leak location. (9,14,15) Subjects initially were instructed to don the respirators according to manufacturers' instructions and perform a user seal check. However, after the first day of testing it was apparent that the user seal checks allowed experienced subjects to adjust nearly every facepiece such that an ''acceptable'' fit was achieved.…”

Section: Methodsmentioning

confidence: 99%

Comparison of Three Commercially Available Fit-Test Methods

Janssen¹,

Luinenburg²,

Mullins³

et al. 2002

AIHA Journal

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American National Standards Institute (ANSI) standard Z88.10, Respirator Fit Testing Methods, includes criteria to evaluate new fit-tests. The standard allows generated aerosol, particle counting, or controlled negative pressure quantitative fit-tests to be used as the reference method to determine acceptability of a new test. This study examined (1) comparability of three Occupational Safety and Health Administration-accepted fit-test methods, all of which were validated using generated aerosol as the reference method; and (2) the effect of the reference method on the apparent performance of a fit-test method under evaluation. Sequential fit-tests were performed using the controlled negative pressure and particle counting quantitative fit-tests and the bitter aerosol qualitative fit-test. Of 75 fit-tests conducted with each method, the controlled negative pressure method identified 24 failures; bitter aerosol identified 22 failures; and the particle counting method identified 15 failures. The sensitivity of each method, that is, agreement with the reference method in identifying unacceptable fits, was calculated using each of the other two methods as the reference. None of the test methods met the ANSI sensitivity criterion of 0.95 or greater when compared with either of the other two methods. These results demonstrate that (1) the apparent performance of any fit-test depends on the reference method used, and (2) the fit-tests evaluated use different criteria to identify inadequately fitting respirators. Although "acceptable fit" cannot be defined in absolute terms at this time, the ability of existing fit-test methods to reject poor fits can be inferred from workplace protection factor studies.

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“…Insetting of the sample probe inlet by 1.0 to 1.5 cm has been recommended by some researchers. (8,9) The probe depth reduces the effects of mixing and the potential for the loss of sample on the inside wall of the respirator. The probe is placed directly in front of the mouth to further minimize the effects of mixing.…”

Section: Correction For Within-mask Sampling Biasmentioning

confidence: 99%

An Effective Protection Factor Study of Respirators Used by Primary Lead Smelter Workers

Spear

Dumond²,

Lloyd³

2000

Applied Occupational and Environmental Hygiene

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An industrial hygiene study was conducted at a primary lead smelter to determine the effective protection factors for negative pressure and powered air purifying half-mask respirators. The study involved 99 paired personal samples taken in six different work areas, in which randomly chosen subjects from the workforce wore dual sampling pumps connected to closed-face 37-mm cassettes. The cassettes were attached either to the workers' lapels for exposure measurements outside the respirator or to a ported respirator for exposure measurements inside the respirator. Samples were collected throughout the work shift and analyzed for lead according to National Institute of Occupational Safety and Health (NIOSH) Method 7082. Using particle size distribution data obtained for the same workplaces, the within-mask samples were corrected for sampling bias. The negative pressure half-mask respirators showed a mean effective protection factor of 6.5 and a mean corrected effective protection factor of 4.56, with a 5th percentile less than 0.5. Approximately 80 percent and 90 percent of the effective protection factors and the corrected effective protection factors, respectively, were equal to or less than the assigned protection factor of 10. For the powered air purifying half-mask respirators, the means for effective protection factor and corrected effective protection factor were 18.20 and 11.92, respectively, with a 5th percentile of 1.0 or less. Approximately 90 percent and 95 percent of the effective protection factors and the corrected effective protection factors, respectively, were equal to or less than the assigned protection factor of 50. The uncorrected and corrected within-mask lead concentrations for both types of respirators exceeded the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for lead by 19 percent to 58 percent. These results indicate that the straight application of assigned protection factors to actual workplace situations may not always be appropriate.

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Parameters that Bias the Measurement of Airborne Concentration Within a Respirator

Cited by 30 publications

References 0 publications

Effect of Particle Size on Respiratory Protection Provided by Two Types of N95 Respirators Used in Agricultural Settings

Effect of Particle Size on Respiratory Protection Provided by Two Types of N95 Respirators Used in Agricultural Settings

Comparison of Three Commercially Available Fit-Test Methods

An Effective Protection Factor Study of Respirators Used by Primary Lead Smelter Workers

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