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Control of Industrial Major Accident Hazards (CIMAH) Report Page 16
Ranhill SAJ Sdn. Bhd. Revision 01
Part D: Information on the Potential Major Accident Date Aug 2019

D.2.5.2 Toxic Gas Dispersion

The potential major accidents are modelled by software to visualise the location of
facility/plant and extend of impacts (on people, plant and surrounding of the plant)
which are indicated on the plant layout and map.

Major accidents of Chlorine gas dispersion modelled using the Lakes Environmental
TM
SLAB View software or equivalent software. The dense gas dispersion used in the
software is SLAB model. The SLAB model is an atmospheric dispersion model for
denser-than-air releases, developed in 1990 by Donald L. Ermak of the Lawrence
Livermore National Laboratory, Livermore, California, with support from the U.S.
Department of Energy (DOE), USAF Engineering and Services Center, and the
American Petroleum Institute. The types of releases treated by the model include
ground-level evaporating pool, an elevated horizontal jet, a stack or elevated vertical
jet, and an instantaneous volume source.
The input data to the physical effects modelling software is based on the following
parameters:

• Type of hazardous substance (physical and chemical property)
• Process or storage condition (pressure, temperature, etc)
• Type of process /storage equipment (size, shape and orientation)
• Layout arrangement (terrain, barrier, etc)
• Weather condition (temperature, humidity, wind speed)

SLAB produces outputs of chemical concentrations at various positions downwind
and at specified heights above the ground.

Physical Effects Contours of Major Accidents are provided in Appendix D1.