The incident left two people in hospital, as a precautionary measure.
Workers carried out emergency procedures at 7.30am after they noticed an odour and began feeling nauseous.
The gas was released during the compacting of a container.
Mayor Tracey Roberts praised the 24 staff, fire, emergency services and ambulance officers for their quick response and she also 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.
‘I would implore members of the community to do the right thing with their recycling bins.
‘Do not put contaminated material in the recycling bins ” this impacts negatively on people’s lives and their livelihoods.’