A spokesman for Vale said the incident would not have an impact production as the leak occurred just as Vale was beginning a scheduled maintenance shutdown at the nickel smelter.
The cleaning procedure normally only creates a small, and manageable, amount of the gas, Kuzenko said.
The noxious gas emergency began with loud sirens at around 6 a.m. Trevor Bain, the local paramedic and fire chief, said trucks arrived at 6:12 a.m.to address the situation. The Vale mining company said there was a nitrogen dioxide release from its Copper Cliff facility on Thursday, August 13, 2015.
When asked about evacuation procedures for Copper Cliff residents in case of an emergency, Kuzenko said Vale is working with the city to put a plan in place, but added an evacuation would not have been an appropriate response Thursday morning, since people were asked to avoid being outside.
She said the workers were all treated and no one was seriously harmed.
Broadcaster CBC earlier reported a yellow plume was visible above the Vale complex – and that cars were being directed away from the smelter.
“As we do a post-mortem and find out exactly what happened, we’ll know more about the levels that were released, but at this point in time, it doesn’t appear that there was any danger to anyone in the community”.
Sudbury authorities say a toxic gas leak at a nearby mining facility has been contained.
Roads around the facility have been closed to traffic.