Journal of occupational and environmental hygiene
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J Occup Environ Hyg · Jan 2014
A quantitative assessment of the total inward leakage of NaCl aerosol representing submicron-size bioaerosol through N95 filtering facepiece respirators and surgical masks.
Respiratory protection provided by a particulate respirator is a function of particle penetration through filter media and through faceseal leakage. Faceseal leakage largely contributes to the penetration of particles through a respirator and compromises protection. When faceseal leaks arise, filter penetration is assumed to be negligible. ⋯ Relatively, higher efficiency N95 and SM models showed lower TIL values. Filter efficiency of FFRs and SMs influenced the TIL at different flow rates and leak sizes. Overall, the data indicate that good fitting higher-efficiency FFRs may offer higher protection against submicron-size bioaerosols.
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J Occup Environ Hyg · Jan 2014
Effect of upper strap downward displacement on n95 filtering facepiece respirator fit factors: a pilot study.
Fifteen subjects underwent three replicates of quantitative respirator fit-testing with N95 filtering facepiece respirators that were donned with the upper strap high on the occiput, as per the manufacturers' donning instructions. Each fit-test was immediately followed by repeat fit-testing with the upper strap downwardly displaced to the level of the ear sulcus to determine any change in fit factors that might occur with upper strap downward slippage. ⋯ Geometric mean fit factors for the initial passed fit-tests, and following downward strap displacement, were 217 ± 1.6 and 207 ± 1.9, respectively (p = 0.64). Downward displacement of the top strap did not significantly impact fit factors of N95 FFRs that had previously passed fit-testing.
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J Occup Environ Hyg · Jan 2014
Novel approach for suppressing cutting dust using foam on a fully mechanized face with hard parting.
The cutting dust created by the shearer drum is the main source of dust on a fully mechanized coal face. However, overexposure to respirable dust may cause pneumoconiosis in coal workers, while coal dust may lead to serious explosions. The fully mechanized face known as II1051 Face, found at the Zhuxianzhuang Coal Mine located in east China, generates dust by way of the drum on a high-power shear. ⋯ The respirable dust exposure levels were reduced from 378.4 mg/m(3)to 53.5 mg/m(3)and the visibility was enhanced dramatically. Thus, we conclude that our new foam system is highly efficient at capturing cutting dust, and it has a much lower water consumption. [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: Contact angle of cutting dust sample, migration trajectory of cutting dust, technological process for suppressing shearer cutting dust using foam, the layout of the foam dust suppression system on coal face, real object of the air self-suction type foam generator, the special foam nozzle used for shearers, relevant experimental results of the air self-suction foam system.].
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J Occup Environ Hyg · Jan 2014
Efficacy of face shields against cough aerosol droplets from a cough simulator.
Health care workers are exposed to potentially infectious airborne particles while providing routine care to coughing patients. However, much is not understood about the behavior of these aerosols and the risks they pose. We used a coughing patient simulator and a breathing worker simulator to investigate the exposure of health care workers to cough aerosol droplets, and to examine the efficacy of face shields in reducing this exposure. ⋯ Thus, face shields provide a useful adjunct to respiratory protection for workers caring for patients with respiratory infections. However, they cannot be used as a substitute for respiratory protection when it is needed. [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: tables of the experiments performed, more detailed information about the aerosol measurement methods, photographs of the experimental setup, and summaries of the experimental data from the aerosol measurement devices, the qPCR analysis, and the VPA.].
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J Occup Environ Hyg · Jan 2014
Comparative StudyComparison of means of two lognormal distributions based on samples with multiple detection limits.
The problem of comparing the means of two lognormal distributions based on samples with multiple detection limits is considered. Tests and confidence intervals for the ratio of the two means, based on pivotal quantities involving the maximum likelihood estimators, are proposed. ⋯ The proposed approach can also be applied to find confidence intervals for the difference between the means of the two lognormal distributions. Illustrative examples with a real data set and with a simulated data set are given.