Contaminant dispersion in the vicinity of a worker in a uniform velocity field

The transportation of gaseous contaminant from a low and moderate tow impul se (momentum < 1 m s(-1)) source to the breathing zone was studied in a uni form air stream flow. Results of the effects of the direction and the veloc ity of principal air flow, convection due to a human body, arm movement of a human being and the type of source on the concentration profiles are pres ented. Three important results were obtained. Firstly, for a given low and moderate impulse low impulse contaminant source in the near field of a work er, his/her orientation relative to the principal air flow direction is the most important factor in reducing occupational exposure, with an air veloc ity of about 0.3 m s(-1). Secondly, the effect of convection resulting from body heat on air flow was lower than expected. Thirdly, arm movements infl uence contaminant dispersion, and should be included when models assessing exposure are developed. The present data can also be used to validate exist ing computational fluid dynamic (CFD) models. (C) 2000 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved.