ABSTRACT
This chapter shows the importance of having knowledge about the interaction between air movements and dispersion of contaminants when contamination risks are assessed. The risk of contamination does not only depend on the concentration of the contaminants, which is of critical importance, but also the motion of the contaminants. If particulate contaminants are being considered, then it is the rate of incidence of the particles that characterizes the risk. The expression for the contamination risk in the main flow direction of a unidirectional air flow is proportional to air velocity and concentration, while the expression for a vortex is more complicated. The air flow often leads to stagnation regions in front of machinery and working surfaces situated perpendicular to the main flow direction. Contamination risks can also occur at electrostatically charged surfaces, which can increase the deposition of particles up to several orders of magnitude. The risk of contamination is more intimately associated with the flux vector than with concentration.
