Imperial Oil personnel responded to a vapour release of hydrogen sulfide around 11:30am holiday Monday.
Company spokesman Jon Harding says the leak from a pipeline at the Christina St. S. refinery was isolated by about 11:45am.
Site sirens sounded and Harding says there was communication with the community and appropriate authorities.
He says monitoring at Imperial's fence line was showing no impact to air quality.
A Chemical Valley Emergency Coordinating Organization alert was initially issued calling for road closures around the facility but within minutes that was cleared.
Harding says there were no injuries and the event has had no impact on Imperial's ability to supply refined products.
The all clear was given at about 1pm.
