Particle samplers are widely used in workplaces in order to determine the concentration of airborne particles in the atmosphere. They generally operate by drawing air, with the aid of a pump, through one or more orifices in the sampler body and housed within the sampler is a filter through which the air is subsequently drawn. The airborne particles are collected on the filter and their concentration is determined. Various samplers have been designed for this purpose including "static" samplers, which are located in a fixed position in a working environment and determine the dust concentration averaged over a prescribed period of time at that one point, and "personal" samplers which are mounted on a working person near to the breathing zone. The ORB sampler, a static sampler designed by Ogden and Birkett (1978) to have approximately the same entry efficiency, for particles with aerodynamical diameter up to at least 25~m, as a human head equally exposed to all wind directions for wind speeds between 0 and 2. 75m1s, is shown in Fig. l. l and examples of personal samplers are shown in Fig. 1. 2a, b and c and represent a single 4mm hole sampler, a seven hole sampler and a 25mm open face filter holder respectively. These three samplers are some of the most commonly used personal samplers for sampling the total airborne concentrations of workplace dusts in Britain.

Klappentext

The sampling of airborne particles in an environment is very important in assessing the risk to health of workers and many blunt sampling devices have been designed for this purpose. In this book sampling by aerodynamically blunt bodies is investigated mathematically for different situations. Existing approaches to the problem are described and improved upon. Also, a new approach is described which includes the use of the Boundary Integral Equation method. This method has advantages over other methods in that it makes it possible to consider samplers of various shapes with sampling taking place at arbitrary positions and includes the finiteness of the orifice in the model. One particular sampler, the human head, is investigated in detail. Also, using an analytical approach, the effects upon aspiration of the particle shape and the finite particle Reynolds number are investigated.

Inhalt
1 General Introduction.- 2 A Review of Past Work on Particle Sampling.- 3 A Comparison of Analytically Derived Expressions in Blunt Body Sampling with those Derived Empirically.- 4 A Boundary Integral Equation Analysis of Blunt Body Sampling in Two Dimensions.- 5 Mathematical Investigation of the Sampling Efficiency of a Two-Dimensional Blunt Sampler.- 6 The Effects of the Particle Reynolds Number on the Aspiration of Particles into a Blunt Sampler.- 7 The Aspiration of Non-Spherical Particles into a Bulky Sampling Head.- 8 An Empirical Model for the Aspiration Efficients of Blunt Aerosol Samplers Orientated at an Angle to the Oncoming Flow.- 9 Use of the Boundary Element Method for Modelling Three- Dimensional Samplers.- 10 The Human Head as a Blunt Aerosol Sampler.- 11 Conclusions.- References.