Search

The Simplified Test Protocol, developed in our earlier studies for testing personal inhalable aerosol samplers, was evaluated in a specially designed small open-section, close-loop wind tunnel. The sampling efficiencies of three personal inhalable aerosol samplers (IOM, GSP, and Button Aerosol Sampler) were measured with 65 μm particles, using the Simplified Test Protocol at four inlet orientations to the wind ( 0, 90, 180 , and 270°). The results were compared with the data collected from other evaluation approaches. Analysis of variance (ANOVA) has shown that there is no statistically significant difference in the samplers’ performance when they are tested in the small and large wind tunnels following the Simplified Test Protocol and in the large wind tunnel following the conventional approach (samplers on a full-size human manikin). Thus, the Simplified Test Protocol has been shown to be suitable for the performance evaluation of personal inhalable aerosol samplers. The new wind tunnel facility was also found useful for handling very large particles, which is a considerable advantage over traditional wind tunnels. Our new wind tunnel was successfully used to measure the sampling efficiencies of the IOM, GSP, and Button Aerosol Sampler when challenged with particles of up to approximately 250 μm aerodynamic diameter at wind velocities of 50 and 100 cm s −1 . The data show that the sampling efficiency of the IOM sampler depends significantly on the wind velocity and is above 100% for particles of 165 and 241 μm mass median aerodynamic diameter. This dependence is not statistically significant for the GSP and Button Aerosol Sampler, whose sampling efficiencies are similar to each other and do not change with increasing test particle size at the indicated wind velocities. Also, the sampling efficiencies of the GSP and Button Aerosol Sampler closely follow the independent data obtained by using a breathing and rotating manikin at a wind velocity of 100 cm s −1 . The new wind tunnel design is expected to enhance the ability to extend the inhalable convention beyond 100 μm .

Traditional protocols for the performance evaluation of personal inhalable aerosol samplers utilize full-size manikins and large cross-section wind tunnels. Thus, these sampler evaluation procedures are complex, very costly, and time consuming. In addition, it is difficult to provide an adequately uniform wind velocity and aerosol concentration over large cross-section wind tunnels. A simplified test protocol, developed in our recent studies, is evaluated in this paper. The protocol is based on a three-dimensional rectangular simplified torso that simulates the dimensions of the human chest. This arrangement allows simultaneous measurement in four discrete orientations to the wind, thus providing useful orientation-dependent sampler information and possibly reducing the number of measurements needed. Sampling efficiencies of four personal inhalable aerosol samplers (the IOM, GSP, 37-mm closed-face cassette, and the button sampler) were measured using the simplified test protocol and the traditional approach for three particle sizes (7, 29, and 70 μ m) in four inlet orientations to the wind (0, 90, 180, and 270°) and two wind velocities (0.5 and 2.0 m s -1 ). It was found that when these samplers were mounted on the simplified torso versus the full-size manikin, the sampling efficiencies responded to changes in the sampling conditions in the same way regardless of whether the samplers were mounted on the simplified torso or the full-size manikin. Also, the sampling efficiencies were found not to be statistically different when the samplers were mounted on the simplified torso versus the full-size manikin. Thus, the simplified test protocol was shown to be suitable for the performance evaluation of personal inhalable aerosol samplers.

The presently available protocol for evaluating the performance of personal aerosol samplers according to the inhalable convention is difficult to satisfy as it requires a large cross-section wind tunnel. The present study was initiated to simplify and reduce the cost of the test method by mounting the test samplers on a small, stationary torso instead of a full-size rotating manikin. The simplified torso consisted of a rectangular three-dimensional body (33 cm wide, 21 cm deep, 21 cm high). Replicates of the personal inhalable aerosol sampler under consideration were attached in the center of each vertical face of the simplified torso representing the three principal sampling orientations (facing the wind, turned 90°, and turned 180° to the wind). When the samplers were mounted on a full-size manikin, the air flow in the vicinity of the manikin was found to depend on the sampler location, symmetry of the manikin, and position of the manikin’s arms. On the simplified torso, the magnitude and direction of the air flow near the samplers were found to be comparable to that of the manikin. When subjected to nearly monodisperse aerosol flows (particle size of 70 μm, wind velocity of 50 and 200 cm s-1), both methods yielded aerosol sampling efficiencies that were statistically not different at three major sampling orientations. The advantages of the simplified torso are that fewer measurements need to be made; a smaller, less expensive wind tunnel can be used for the testing; and interlaboratory variability of personal inhalable samplers’ performance may be decreased.

The airflow and particle-velocity patterns in the vicinity of a curved, porous sampling surface constituting the inlet of an aerosol sampler, have been determined by Laser-Doppler Velocimetry. The tests were performed on a personal aerosol sampler with a concave sampling surface, referred to as the “button” sampler. Measurements with the button sampler were conducted in a low-speed, open-circuit, horizontal wind tunnel using two types of monodisperse aerosols: 2 μm essentially inertialess propylene glycol particles (their trajectories represent the flow streamlines) and 44 μm inertial fly ash particles. The tests were performed at two free stream velocities (0.5 and 4 m/s) and two sampler orientations (facing the wind and facing downward at 90° to the wind). The sampling flow rate was 2 L/min. Sampling through the curved surface was conducted while the button sampler was freely suspended in the flow or while it was attached to a vertical stagnation plate simulating the human torso. The results in...

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.