Workers enacted emergency procedures at 7.30am after they noticed an odour and became nauseous. The gas was released in the compacting of a container.
Mayor Tracey Roberts praised the 24 staff, fire and emergency services and ambulance officers for their quick response but urged the public to be more responsible.
‘We do all we can from the City’s point of view to ensure worker safety and it’s important the community do the same,’ she said.
She said contaminants should not be put in recycling bins.