Workplace Field Testing of the Pressure Drop of Particulate Respirators Using Welding Fumes

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Hyun-Woo Cho and Chung-Sik Yoon*

Institute of Health and Environment, Department of Environmental Health, School of Public Health, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea ?* Author to whom correspondence should be addressed. Tel: +82-2-880-2734; Fax: +82-2-745-9104; e-mail: csyoon{at}snu.ac.kr Received August 3, 2011. Accepted February 25, 2012. In a previous study, we concluded that respirator testing with a sodium chloride aerosol gave a conservative estimate of filter penetration for welding fume aerosols. A rapid increase in the pressure drop (PD) of some respirators was observed as fumes accumulated on the filters. The present study evaluated particulate respirator PD based on workplace field tests. A field PD tester was designed and validated using the TSI 8130 Automatic Filter Tester, designed in compliance with National Institute for Occupational and Safety and Health regulation 42 CFR part 84. Three models (two replaceable dual-type filters and one replaceable single-type filter) were evaluated against CO2 gas arc welding on mild steel in confined booths in the workplace. Field tests were performed under four airborne concentrations (27.5, 15.4, 7.9, and 2.1 mg m-3). The mass concentration was measured by the gravimetric method, and number concentration was monitored using P-Trak (Model 8525, TSI, USA). Additionally, photos and scanning electron microscopy–energy dispersive X-ray spectroscopy were used to visualize and analyze the composition of welding fumes trapped in the filters. The field PD tester showed no significant difference compared with the TSI tester. There was no significant difference in the initial PD between laboratory and field results. The PD increased as a function of fume load on the respirator filters for all tested models. The increasing PD trend differed by models, and PD increased rapidly at high concentrations because greater amount of fumes accumulated on the filters in a given time. The increase in PD as a function of fume load on the filters showed a similar pattern as fume load varied for a particular model, but different patterns were observed for different models. Images and elemental analyses of fumes trapped on the respirator filters showed that most welding fumes were trapped within the first layer, outer web cover, and second layer, in order, while no fumes were observed beneath the fourth layer of the tested respirators. The current findings contribute substantially to our understanding of respirator PD in the presence of welding fumes.

© The Author 2012. Published by Oxford University Press on behalf of the British Occupational Hygiene Society [2012]This ArticleAnn Occup Hyg (2012) 56 (8): 948-958. doi: 10.1093/annhyg/mes015 First published online: April 26, 2012 Current Issue

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Laboratory and field measurements and evaluations of vibration at the handles of riveting hammers

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Thomas W. McDowell*, Christopher Warren, Daniel E. Welcome and Ren G. Dong

NIOSH Health Effects Laboratory, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA ?* Author to whom correspondence should be addressed. Tel: (304) 285-6337; fax: (304) 285-6265; e-mail: TMcDowell{at}cdc.gov Received October 18, 2011. Accepted February 20, 2012. The use of riveting hammers can expose workers to harmful levels of hand-transmitted vibration (HTV). As a part of efforts to reduce HTV exposures through tool selection, the primary objective of this study was to evaluate the applicability of a standardized laboratory-based riveting hammer assessment protocol for screening riveting hammers. The second objective was to characterize the vibration emissions of reduced vibration riveting hammers and to make approximations of the HTV exposures of workers operating these tools in actual work tasks. Eight pneumatic riveting hammers were selected for the study. They were first assessed in a laboratory using the standardized method for measuring vibration emissions at the tool handle. The tools were then further assessed under actual working conditions during three aircraft sheet metal riveting tasks. Although the average vibration magnitudes of the riveting hammers measured in the laboratory test were considerably different from those measured in the field study, the rank orders of the tools determined via these tests were fairly consistent, especially for the lower vibration tools. This study identified four tools that consistently exhibited lower frequency-weighted and unweighted accelerations in both the laboratory and workplace evaluations. These observations suggest that the standardized riveting hammer test is acceptable for identifying tools that could be expected to exhibit lower vibrations in workplace environments. However, the large differences between the accelerations measured in the laboratory and field suggest that the standardized laboratory-based tool assessment is not suitable for estimating workplace riveting hammer HTV exposures. Based on the frequency-weighted accelerations measured at the tool handles during the three work tasks, the sheet metal mechanics assigned to these tasks at the studied workplace are unlikely to exceed the daily vibration exposure action value (2.5 m s-2) using any of the evaluated riveting hammers.

Published by Oxford University Press [2012] on behalf of the British Occupational Hygiene SocietyThis ArticleAnn Occup Hyg (2012) 56 (8): 911-924. doi: 10.1093/annhyg/mes022 First published online: April 26, 2012 Current Issue

Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.

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