Toxic gas at a Whanganui tannery left four workers unconscious, with two of them having to be placed in induced comas to recover.
Tasman Tanning pleaded guilty in the Whanganui District Court to one charge of failing to take all practicable steps to ensure the safety of its workers.
It was fined $73,000 and ordered to pay $90,000 in reparations to the workers.
Workers at the tannery were exposed to hydrogen sulphide gas in November 2012 after two chemicals used in the leather-making process, sulphuric acid and hydrosulphide, were mixed.
The gas knocked out two workers, Joseph Ratana and Warren Burgess, on the mezzanine floor of the tannery.
A third man, Taniela Balivou, fell unconscious when he attempted to go to their aid and another worker involved in rescue efforts also passed out briefly.
The tannery was evacuated and the unconscious men were eventually pulled from the building by co-workers, who found two breathing masks that enabled them to make it up to the mezzanine.
Ratana and Burgess were sent to hospital and placed into medically induced comas as part of their treatment.
The pair suffered short-term memory loss and temporary loss of sight. Balivou regained consciousness outside the tannery.
The incident prompted an investigation by WorkSafe New Zealand, which led to the charge being laid.
WorkSafe's general manager of investigations, Brett Murray, said Tasman Tanning could have taken steps to avoid such an incident, including issuing employees with personal gas detectors. The detectors would have warned them about the high hydrogen sulphide levels.
"Workers at Tasman Tanning were also not given adequate training to respond to such an emergency," Murray said.
"There was no proper safe operating procedure in place and workers did not ensure their own safety before going to the aid of Ratana and Burgess.
"This resulted in serious harm to some of those employees."
The company could also have had separate chemical storage tanks for each vessel used in the tanning process, Murray said.
"Shared storage tanks meant that substances intended for one vessel could mistakenly be transferred to the wrong vessel.
"The remote location of the holding tank control panel also added to the possibility of an error."
- Fairfax Media