The plume from the boiler stack at Imperial Oil may be more visible for the next 24 to 36 hours.
There was an unplanned shutdown at the Sarnia refinery's CO boiler aroound 10:30pm Monday.
Refinery personnel are working to restart the boiler to normal operations.
Imperial says the Ministry of Environment has been notified, and the company does not expect emissions to exceed government guidelines.
The Sarnia refinery does not anticipate the related work on the main boiler will have any impact on the supply of refined products.
