Prediction of Exposure Levels in an Uncontrolled Toxic Gas Release

By Mansoor Mollagee.

Published by The Technology Collection

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Article: Electronic $US5.00

In July 2002, a toxic gas release from a waste stack affected a large number of people in one of South Africa’s key industrial zones. An Investigation Panel was set up by the relevant Provincial authorities to determine the cause of the accident. The findings suggested that a combination of technical and managerial shortcomings may have given rise to the accident. A Regression Model was developed in order to determine the degree of exposure. The concentration of Sulphur Dioxide (SO₂) gas at the top of the stack was calculated as 3300 ppm with a ground-level concentration of 1000 – 2000 ppb. A more thorough investigation was commissioned by National Government. The technical investigation provided the basis for the work covered in this paper. The regression model was re-examined employing two different techniques to mitigate the effect of model disposition. An area of maximum exposure was defined based on the direction in which the plume traveled in order to determine the inhalation dosage at the point of greatest contact. The findings suggest that the levels of SO₂ inhaled exceeded the National Institute for Occupational Health (NIOSH), World Health Organisation (WHO) and Department of Environmental Affairs and Tourism (DEAT) IDLH exposure limits. This prompted more exhaustive analysis of the event. Since insufficient data was available to pursue the scientific route further, a cause-effect relationship was established between the calculated level of exposure and the injuries sustained by some of the victims.
This study suggests that despite our scientific advances, the adverse impact that technology may have on society such as in the case of industrial catastrophes can be minimized when knowledge is more effectively employed in the workplace in trying to avert the occurrence or when dealing with the after-effects.

Keywords: Sulphur Dioxide, Toxic Gas Release, Acid Ingestion, Exposure Levels, Plume Model

The International Journal of Technology, Knowledge and Society, Volume 6, Issue 2, pp.181-190. Article: Print (Spiral Bound). Article: Electronic (PDF File; 731.582KB).

Mansoor Mollagee

Head of Department, Department of Chemical Engineering, Faculty of Engineering and the Built Environment, University of Johannesburg, Johannesburg, Gauteng, South Africa

Primary research interests are in the area of turbulence modeling and Computational Fluid Dynamics, particularly wall-particle interactions under different flow conditions. Other interests include Dispersion Modelling of atmospheric pollutants, where a successful model has recently been developed in conjunction with the National Department of Environmental Affairs. A methodical approach to teaching, learning and research is of special interest in current position. The present work is part of a greater scheme in which the academic rigours associated with research is systematically applied to different scenarios via pro-active engagement with broader society through the application of technological innovation.

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