A study of external flow effects on personal sampling. Final report on CEC Contract 7253-22/8/089

An experimental investigation has been carried out to examine the effects of the external air flow on the performances of personal dust samplers used in occupational hygiene for sampling inhalable dust in the workplace. The point of view has been taken that personal samplers form a special category within the wider family of blunt samplers. All the work was carried out in laboratory wind tunnels using inert subjects under simulated workplace conditions, and consisted of two main complementary phases. The first consisted of a study of the dust sampling characteristics of the human head (to allow inhalable dust to be defined), and of the performances of a number of commercially-available personal samplers mounted on a model torso. The second consisted of a basic theoretical and experimental study of the performance characteristics of blunt samplers in general, as a result of which a plausible physical model of the physics was developed. This model was applied to the personal sampler results of the first phase. The main conclusion was that sampling efficiency was the least sensitive to variations in ambient wind speed at the highest sampling velocities. The problem of external wall losses and their effect on the sampling characteristics of personal samplers was investigated, and found to be potentially significant for “”real”” dusts (although not so for liquid droplet aerosols such as those often used in laboratory research).The project has provided considerable physical insight into the behaviour of dust sampling devices in moving air, and allows criteria to be set for their optimum practical use. “”