"He was hurt when the drum exploded. It exploded with all the chemicals away from him. It blew the lid off the drum. When the lid came back that's what hit his hand. I don't believe anything was broken."
Mr Couper believed the man was taken to Oamaru Hospital before FENZ teams arrived.
The two chemicals involved, Mr Couper believed, were citric acid and sodium chlorite.
"When it reacts it gives off heat, but also chlorine dioxide gas - a real nasty. I know when we started diluting it down, the gas cloud was a green-yellowy colour. It's pretty dangerous stuff."
"Massive amounts" of water were used to dilute the gas.
The FENZ teams had to deal with about 200 litres of the combined chemical, he said.
It was fortunate the wind direction made it easier to contain the gas and the site location was well away from Oamaru town.
Emergency services were at the site from about 2pm to 6pm.
Mr Couper said firefighting gear was sent away to be cleaned, and firefighters had to go through decontamination showers.
"It was a successful outcome. It obviously could have been a lot worse."
shannon.gillies@odt.co.nz
- The Otago Daily Times
