A 59-year-old man who died at Hobart's Nyrstar Zinc smelter on Wednesday evening has been named as Michael Lewis Petterwood of Risdon Vale.

Key points: The man was found unconscious by a colleague late yesterday evening

The man was found unconscious by a colleague late yesterday evening He was in a section of the smelter that emits sulphur dioxide, according to the union

He was in a section of the smelter that emits sulphur dioxide, according to the union Worksafe Tasmania, police and Nyrstar are investigating, and a report is being prepared for the coroner

Police released his name this afternoon, saying their thoughts were with his family and loved ones.

Emergency services were called to the smelter at Lutana in Hobart's northern suburbs on Wednesday evening, after Mr Petterwood was found unconscious by a colleague.

Police said his cause of death was not yet known, but it was not considered to be suspicious.

In a statement, Nyrstar said it was investigating the incident and was working with Worksafe Tasmania and police.

There were no reports of any other injuries.

Robert Flanagan from the Australian Workers' Union said Mr Petterwood had worked at the Nyrstar smelter for about 32 years and was a well-respected operator.

He said the death had shocked and distressed his colleagues.

Nyrstar said it would offer counselling and other support to colleagues who had been affected.

Worksafe Tasmania has been notified and a report will be prepared for the coroner.

Union flags 'significant' safety concerns

Although it was initially reported Mr Petterwood may have been affected by carbon monoxide, Mr Flanagan said the cause of death was unknown.

"We don't know at this point the cause, if it was natural causes or what not, so Workplace Standards is investigating the matter," he said.

Mr Flanagan said Mr Petterwood was in a part of the plant that emitted sulphur dioxide, but it was also not known what levels, if any, there had been when the man passed away.

"Because of the nature of that part of the plant it's not something that you can flick a switch and turn it off, so there is work continuing," he said.

"But the company has made it clear to the union and the employees that their main priority is the wellbeing of the workforce."

He said the union would be supporting its members and Mr Petterwood's family.

"The end priority at the moment is to provide support to the family and friends of the deceased worker," he said.

"There are significant safety concerns, but now is not the time for us to discuss that."