Last Tuesday, the Ravensdown Dunedin works released thick white clouds into the air.
Neighbours spoken to last week said the cloud of steam coming from the plant made it appear the place was on fire.
The vapour was “clearly not coming from the stack”, but was coming from the factory itself, they said.
A Ravensdown spokesman said the discharge on Tuesday was “mainly water vapour with trace quantities of fluoride”.
The plant had been shut down for the day for routine cleaning and maintenance.
The cause of the discharge was a hatch used for access which was left unsecured, the spokesman said.
It ran for a 35-min period and ended at 9.05pm.
There may have been small quantities of harmless, though odorous, compounds in the discharge, the spokesman said.
Fluoride could have an effect on sensitive vegetation, but the discharge was “well below” the level where human health was affected, he said.
However, the incident brought up long-running community concerns about pollution in the area.
Otago Regional Council compliance manager Tami Sargeant said the council received a complaint about the discharge.
The complaint was called in by Jacob Parker, who has lived across the road from the site for 12 years.
His time there had been horrible, he said.
Foul odours and noise pollution were regularly present on his property.
Leaving was not an option as the air pollution had damaged his home and nobody would want to live next to the factory, he said.
At one point his home was valued at less than $100,000.
He also believed it would not be morally right to sell up and subject someone else to the “abuse”.
Despite the company saying the discharge was mostly steam, he was still concerned about what it could be doing to people and their homes.
It was not the first time large plumes had come from the factory, he said.
His concerns were shared by other members of the community.
“A lot of it will be steam, but it’s not a bakery, it’s not a cheese factory, it’s a sulphur, synthetic fertiliser plant,” one neighbour said.
The majority of the discharge might be steam, but other chemicals would be mixed in, he said,
“There’s a list — really, really long — of different chemicals which they use.”
Ms Sargeant said the council had been proactively monitoring the Ravensdown site, involving odour assessments to ensure the company was meeting its consent conditions.
There had been three monitoring occasions so far this year and in all cases no offensive or objectionable odours had been determined beyond the property boundary.
She noted staff were not always able to be on site immediately when complaints were received.
The council would continue to monitor the site to ensure compliance, she said.
The Ravensdown spokesman said the incident had been investigated and procedures were put in place to ensure it, or similar incidents, were avoided in the future. — Additional reporting Hamish MacLean
