Radial aerosol transport is driven by turbulent diffusion and some natural convection. The test and reference samplers are equally distributed around the source at the same distance from the centre and operate in parallel (in most of our experiments, the total number of simultaneously operating samplers was 15). In this system, an aerosol generator, which is located in the centre of a room-sized non-ventilated chamber, continuously rotates and omnidirectionally disperses test particles of a specific size. Thus, the first objective of this study was to design and test a new, low cost experimental protocol for measuring the sampling efficiency of personal inhalable aerosol samplers in the vicinity of the aerosol source when the samplers operate in very slowly moving air. Recent surveys suggest that elevated levels of occupational exposure to inhalable airborne particles are typically observed when the worker, operating in the vicinity of the dust source, faces the source. While personal aerosol samplers have been characterized primarily based on wind tunnel tests conducted at relatively high wind speeds, modern indoor occupational environments are usually represented by very slow moving air. Witschger, O Grinshpun, S A Fauvel, S Basso, G Performance of personal inhalable aerosol samplers in very slowly moving air when facing the aerosol source. Overall, there was a significant effect of wind speed on sampling efficiency, with lower wind speeds clearly associated with an increase in sampling efficiency. The results showed that, down to âˆ❀.2 m s(-1), the samplers matched the current inhalability criterion relatively well but were significantly greater than this at the lowest wind speed tested. The samplers that were tested included the Institute of Occupational Medicine (IOM), Button, and GSP inhalable samplers as well as the closed-face cassette sampler that has been (and still is) widely used by occupational hygienists in many countries.
The experimental set-up involved use of a hybrid ultra-low speed wind tunnel/calm air chamber and a rotating, heating breathing mannequin to measure the inhalable fraction of aerosol exposure. It was therefore important to assess the performance of the most common personal samplers used to collect the inhalable aerosol fraction, especially those that were designed to match the original curve.
There is currently some concern about whether the existing inhalable aerosol convention is appropriate at these low wind speeds and an alternative has been suggested. The assessment of personal inhalable aerosol samplers in a controlled laboratory setting has not previously been carried out at the ultra-low wind speed conditions that represent most modern workplaces. Performance study of personal inhalable aerosol samplers at ultra-low wind speeds.
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