A leak of 30 to 40 kg of ammonia occurred in a brewery at 9.15 am while a suction manifold on a refrigeration unit’s compressor was being replaced. Three subcontractors, wearing masks, exited the machine room and were hospitalised for a few hours. The leak stopped 15 minutes later after the suction system valves were closed in a room next to the hall.

At 7.15 am, the manifold had been isolated (by 3 valves) and purged, but the valve on the return line of fermentation tanks’ cold circuit was not closed. The error had not been detected as the 2 pumps and a 1 valve on this circuit are off-load during periods of peak electricity consumption. The leak occurred when they were re-energized.

The environment was not effected, although 100 people were evacuated