In a chemical plant, 11 kg of chlorine leaked around 9.30 am while being transferred in liquid phase from a tanker. The leak lasted for 30 seconds and led to the formation of a 50m cloud at the ground level that drifted with its visible part confined to the site premises. The technicians closed the valves by shutting off the supply of compressed air, sounded the alarm, and activated the water curtains.The technicians who were not equipped with their self-contained breathing apparatus were poisoned by the fumes and taken to the infirmary.The accident resulted from the rupture of the flange joint of a transfer hose during the tightness test. The joint was deformed because of the use of two 2 mm joints instead of one 4 mm joint. The operator who performed the tightening operation was undergoing training: The tightening operation was not properly carried out with the bolting machine. Lastly, the tightness tests were carried out in a chlorine atmosphere instead of nitrogen.Since the flanges were not damaged, the transfer from the tanker was smooth during the afternoon.The operator took several measures after the accident: strict compliance with the safety instruction on wearing a self-contained breathing apparatus, ensuring consistency in issuing permits for various industrial operations, updating technician training on tightening operations, exclusive use of 4 mm joints.

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