This article describes the theoretical considerations, design criteria, and experimental performance of a cyclone-based, liquidfilm, bioaerosol sampler. Different from conventional cyclones, this novel sampler draws air tangentially into the bottom of a swirling cyclone, creating a negative pressure differential which causes continuous suction of sorption liquid from its reservoir into the cyclone. The liquid swirls with the air vortex and rises spirally along the sampler wall in the form of a thin film. In the presence of an excess pressure differential, the liquid goes over the upper edge of the cyclone (overflow mode) and flows back to the bottom of the sampler. As a result, there is a continuous circulation of the sorption liquid in the sampler, which enhances the efficacy of capturing viable aerosol particles from incoming air. In this study, mathematical models using simplified Navier-Stokes equations are developed to describe the behavior of the airflow, the formation of the liquid film, and the precipitation process of the aerosol particles. Numerical solutions are presented as an approximation to these complex air and liquid flow streams in the whirlwind cyclone. Based on the theoretical assessment, practical design criteria for a novel sampler were formulated and a series of prototype samplers were fabricated and evaluated. In this report, experimental findings concerning the thickness of the air vortex, the pressure profile in the cyclone, and the apex height of the liquid film are presented. The results are in good agreement with theoretical prediction. However, the theory seems to overestimate the capturing efficiency for particles around

In this study, the performance of two newly developed personal bioaerosol samplers for monitoring the level of environmental and occupational airborne microorganisms was evaluated. These new personal bioaerosol samplers were designed based on a swirling cyclone with recirculating liquid film. The performance evaluation included collection efficiency tests using inert aerosols, the bioaerosol survival test using viable airborne microorganism, and the evaluation of using non-aqueous collection liquid for long-period sampling. The test results showed that these two newly developed personal bioaerosol samplers are capable of doing high efficiency, aerosol sampling (the cutoff diameters are around 0.7 μm for both samplers), and have proven to provide acceptable survival for the collected bioaerosols. By using an appropriate non-aqueous collection liquid, these two personal bioaerosol samplers should be able to permit continuous, long-period bioaerosol sampling with considerable viability for the captured bioaerosols.

The need to determine occupational exposure to bioaerosols has notably increased in the past decade, especially for microbiology-related workplaces and laboratories. Recently, two new cyclone-based personal bioaerosol samplers were developed by the National Institute for Occupational Safety and Health (NIOSH) in the USA and the Research Center for Toxicology and Hygienic Regulation of Biopreparations (RCT & HRB) in Russia to monitor bioaerosol exposure in the workplace. Here, a series of wind tunnel experiments were carried out to evaluate the physical sampling performance of these two samplers in moving air conditions, which could provide information for personal biological monitoring in a moving air environment. The experiments were conducted in a small wind tunnel facility using three wind speeds (0.5, 1.0 and 2.0 m s −1 ) and three sampling orientations (0°, 90°, and 180°) with respect to the wind direction. Monodispersed particles ranging from 0.5 to 10 μm were employed as the test aerosols. The evaluation of the physical sampling performance was focused on the aspiration efficiency and capture efficiency of the two samplers. The test results showed that the orientation-averaged aspiration efficiencies of the two samplers closely agreed with the American Conference of Governmental Industrial Hygienists (ACGIH) inhalable convention within the particle sizes used in the evaluation tests, and the effect of the wind speed on the aspiration efficiency was found negligible. The capture efficiencies of these two samplers ranged from 70% to 80%. These data offer important information on the insight into the physical sampling characteristics of the two test samplers.

This article describes the development of a novel, high-performance personal aerosol sampler intended to monitor occupational air pollution, specifically, microbial constituents. This prototype sampler has a horizontally positioned conical cyclone with recirculating liquid film and an ejection supply of adsorptive liquid into the inlet nozzle. Airborne pollutants were collected in the adsorptive liquid, thus improving the survivability of microbiological aerosol samples. Experimental modules of different dimensions were first evaluated. Based on the test results, a prototype sampler was fabricated and tested. Evaluation of the collection efficiency of the prototype unit indicated a higher than 90% collection efficiency for particles > 1.0 microm. The 50% cutoff diameter was between 0.70-0.75 microm. For assessment of the sampling process effect on the collected microorganisms, Bacillus thuringiensis was tested at a concentration of about 1.0 x 10(6) cells per cm(3). The viability in the prototype sampler decreased to 78% after 60 min of operation.

In this study the performance of two newly developed personal bioaerosol samplers was evaluated. The two test samplers are cyclone-based personal samplers that incorporate a recirculating liquid film. The performance evaluations focused on the physical efficiencies that a personal bioaerosol sampler could provide, including aspiration, collection, and capture efficiencies. The evaluation tests were carried out in a wind tunnel, and the test personal samplers were mounted on the chest of a full-size manikin placed in the test chamber of the wind tunnel. Monodisperse fluorescent aerosols ranging from 0.5 to 20 microm were used to challenge the samplers. Two wind speeds of 0.5 and 2.0 m/sec were employed as the test wind speeds in this study. The test results indicated that the aspiration efficiency of the two test samplers closely agreed with the ACGIH inhalable convention within the size range of the test aerosols. The aspiration efficiency was found to be independent of the sampling orientation. The collection efficiency acquired from these two samplers showed that the 50% cutoff diameters were both around 0.6 microm. However the wall loss of these two test samplers increased as the aerosol size increased, and the wall loss of PAS-4 was considerably higher than that of PAS-5, especially in the aerosol size larger than 5 microm, which resulted in PAS-4 having a relatively lower capture efficiency than PAS-5. Overall, the PAS-5 is considered a better personal bioaerosol sampler than the PAS-4.