The owners of the Grangemouth site in Scotland will open the petrochemical plant and the oil refinery immediately after both were shut down last week over an industrial dispute.
The move follows acceptance by the Unite union of a survival plan, including a pay freeze, ending of the final salary pension scheme and other changes to terms and conditions.
An undisclosed number of contractors have been laid off or switched to other sites.
Grangemouth owners Ineos are in last ditch talks with the workers' union, but the workforce is just one of the problems facing the plant.
Thousands of jobs are under threat after a dispute over conditions led to a shock decision to close the petrochemical site in Grangemouth.