Imperial Oil is reporting that darker than normal stack emissions may be noticed for several days at its Sarnia refinery.
In a message on the Community Awareness and Emergency Response Line, spokesperson Kristina Zimmer said they are conducting required maintenance on process equipment.
"The stack emission is petroleum coke, which is a refinery byproduct," said Zimmer.
She said the repairs to the process equipment are a proactive measure to maintain safe and continuous operation of the facility.
Zimmer said the Ministry of Environment has been notified.