The exact cause of an unplanned incident at NOVA Chemicals Corunna Wednesday is under investigation.
NOVA Chemicals now says one of their fixed monitors in one of its units indicated elevated hydrogen sulphide levels just before 5pm.
As a precaution, evacuation alarms at the St. Clair Township plant sounded in an effort to move employees and contractors to a safe location, and a CVECO Code 8 was issued.
Company officials say the event was isolated to a small area of the unit and ongoing air-monitoring along the perimeter of the unit indicated no readings.
The all-clear was issued about an hour later at 5:50pm.
The NOVA Corunna site is still in the process of restarting the facility after a planned maintenance shutdown which began in August.
As the plant is brought back online, periods of elevated flaring and some increased noise are expected.
