J. Smith

Performance Characteristics of the Button Personal Inhalable Aerosol Sampler

The button inhalable aerosol sampler with a curved porous inlet recently was developed and evaluated as a stationary sampler in the laboratory and in the field. The present study focused on investigating its suitability for personal inhalable aerosol sampling. The button sampler was tested at two wind velocities (0.5 and 2.0 m/sec), three particle sizes (7, 29, and 70 microm) and three orientations to the wind (0, 90, and 180 degrees). The performance characteristics of the button sampler were compared with those of three other personal samplers--the IOM (Institute of Occupational Medicine), GSP, and 37-mm closed-face filter cassette. The experiments were conducted in a wind tunnel with the samplers mounted on a full-size manikin. The direction-specific sampling efficiency of the button sampler was found to be essentially independent of the wind direction and dependent on the wind velocity to a much smaller degree than that of the three other samplers. When direction-averaged, the fit of its sampling efficiency curve to the inhalability curve was found to be better than that of the 37-mm closed-face cassette, comparable with that of the GSP sampler, and less than that of the IOM sampler. The precision of the button sampler was found to be generally equal to or better than the precision of the comparison samplers. It was concluded that the button sampler can be successfully used as a personal inhalable aerosol sampler.

Laboratory Investigation of the Mass Stability of Sampling Cassettes from Inhalable Aerosol Samplers

A study was conducted to evaluate the mass stability of the materials used in the construction of samplers with internal cassettes for the gravimetric measurement of inhalable aerosol exposures. The internal cassettes from IOM samplers were studied. Results indicate that the mass stability of filters is uniform, but the mass stability of the cassette material may dramatically affect the results of the measurement. Cassettes constructed from plastic exhibited drastic shifts in mass depending on the environmental conditions of their storage. Under room humidity, the plastic cassettes absorbed 1 to 2 mg of water over several days. When these cassettes were placed in a desiccator, they lost mass consistently but did not approach a stable mass. Studies repeated with cassettes made of stainless steel showed negligible mass variability. Based on this study, the use of stainless steel cassettes is recommended for gravimetric determinations of aerosol exposure, although field blanks may in some cases be used for correction of data from plastic cassettes. This study shows the need to evaluate the mass stability of the cassette material of any sampling device where an internal cassette is weighed together with the filter.

Development of a Large Particle Aerosol Distribution System for Testing Manikin-Mounted Samplers

Personal samplers used to determine the inhalable fraction of workplace dust are tested while mounted on a manikin, which simulates a worker. To understand the mechanisms affecting the performance of such samplers, researchers must measure the airflow around the body where the samplers are mounted. Therefore, wind tunnel facilities to determine both airflow conditions around samplers and sampling efficiency are needed. A wind tunnel system was developed that was large enough to accommodate the top half of a life-sized manikin and employed a laser Doppler velocimeter for velocity measurements around the manikin. For generating particles up to 70 μm, an aerosol generation system, using a two-dimensional scanning system to cover an extended area, was developed and tested. The generation system had carriages with linear bearings mounted on rod assemblies for scanning in the horizontal and vertical directions. Screw drives, powered by stepper motors under computer control, moved the carriages in a preprogrammed pattern. The generation system was characterized for its ability to generate uniform concentrations of aerosols over an extended area at wind speeds of 0.5 and 2 m/s and particle sizes of 7 and 70 μm. Uniformity of concentration over the area studied, in the absence of the manikin, was 10% relative standard deviation (RSD) or better, except for 7 μm particles at a wind speed of 0.5 m/s where some nonuniformity was observed. The uniformity under these conditions was improved by rearranging the distances between components in the wind tunnel.

Effect of Sampler and Manikin Conductivity on the Sampling Efficiency of Manikin-Mounted Personal Samplers

Experiments were performed that examined how the electrical conductivity of personal samplers and the manikin on which the samplers were mounted affected sampling efficiency. These experiments were done in a wind tunnel using a 7 w m Mass Median Aerodynamic Diameter (MMAD) aerosol with conductive Institute of Occupational Medicine (IOM) samplers and conductive and nonconductive 37 mm cassettes mounted on a life-sized manikin, which was conductive or nonconductive. The charge on the aerosol was neutralized for some experiments. Nonconductive samplers gave lower sampling efficiency than conductive samplers for both the conductive manikin and nonconductive manikin, and the nonconductive manikin gave lower sampling efficiencies with both conductive and nonconductive samplers. These effects were smaller at reduced levels of charge on the aerosol. It is important to consider the conductivity of the manikin when designing experiments to determine the sampling efficiency of personal samplers mounted on a manikin.

Uses and selection of equipment for engineering control monitoring.

Control monitoring (continuous multipoint monitoring of workplace air) has been used in a number of industries to help control worker exposure to a wide variety of contaminants. Control problems were identified and effective control has been maintained by keeping workers and management aware of pollutant levels in the workplace. To be used effectively, the control monitoring system must be viewed as an integral part of workplace control. In this report, the general uses of control monitoring equipment are given, the factors to be considered in choosing equipment for control monitoring purposes are discussed, and a number of advances such as the development of sampling and data acquisition and display components that would help to promote the future use of control monitoring equipment are given. The role of control monitoring in workplace control is examined by looking at the interactions of the control monitoring system with the other elements of workplace control (engineering control devices, work practices, and personal protective equipment).

U.S. Approach for Air Sampling of Workplace Contaminants: Current Basis and Future Options

Abstract The evaluation and control of the workplace environment and worker exposures to air contaminants require an understanding of the levels of those air contaminants. In the past 20 years, the emphasis has been on monitoring specific chemical vapors and aerosols. The approach that has been taken, the reason for that approach, and the progress that has been made are the primary topics of this article. Another topic of this article concerns the future of workplace monitoring with regard to new instrumentation, instrument and computer networking, the growth of biotechnology, and concerns about indoor/office environments and the agriculture setting. Bierbaum, P.J.; Doemeny, L.J.; Smith, J.P.; Abell, M.T.: U.S. Approach for Air Sampling of Workplace Contaminants: Current Basis and Future Options. Appl. Occup. Environ. Hyg. 8(4):247-250; 1993.