At a chemical plant, a large cloud of phosphorus trichloride (PCl3) and hydrogen chloride was released during a degassing test conducted on a PCl3 iso-container damaged during an incident that same morning (ARIA 26003). The plant’s internal emergency plan was activated for 20 min. As a preventive measure, site personnel wore self-breathing apparatuses and water curtains were set up. However, the test technician sustained slight burns to his legs due to the sprayed PCl3, while the driver suffered from exposure to acid vapours. Given the change in wind direction (west, 10 m/s), adjacent sites were not affected by the cloud, though the neighbouring chemical facility still triggered its emergency plan. Handling the manual valve on the dip tube instead of the vent opening valve caused this accident. The slightly pressurised PCl3 in the container warmed by the sun spurted through the unprotected dip tube via a flush joint. As a result of pressure in the sun-warmed container, PCl3 rose through the unprotected dip tube when the valve was opened by mistake. As an exceptional on-site procedure, degassing was initiated after assessing the situation, yet without following the safety and analysis instructions, which specifically indicated the lists of points to be examined. The container was ultimately returned to the supplier to drain the PCl3, perform maintenance and bring the equipment up to code. To lessen the chances of recurrence, various measures were implemented: acceptance certification adopted for all new packaging, and drafting of PCl3 leak prevention procedures.

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