In a Seveso chemical plant, some 2.5 kg of ammonia were released into the atmosphere around 1:15 pm following malfunction of a gas scrubber and resulting in an odour nuisance. Someone outside the facility sounded the alarm. The component was stopped then turned back on. No staff members reported being inconvenienced and plant production was not interrupted. The incident arose subsequent to a change in the process control system. In reality, the recommended flow rate of saltwater used in the carbonation tower gas scrubber was not carried over to the new system. Upon start-up, the saltwater flow rate had remained at a minimum, corresponding to the workshop’s nominal operating level. Given ongoing production demands, this flow rate proved to be insufficient for complete gas washing (CO2 and NH3), hence the release of NH3.