Two separate employers
The contractor is the employer in respect of their own workers and carries their own duties. The principal employer does not take those duties over, but is responsible for coordinating work running in the same workplace and for informing.
Information runs both ways
The principal informs the contractor of the workplace's hazards and emergency arrangements; the contractor informs the principal of the hazards the work brings. One-way information leaves a gap neither side can see.
Shared areas and simultaneous work
Overlapping jobs can be dangerous together even when each is safe alone. Who works where and when in shared areas is arranged through permits and coordination meetings.
Records
The existence of training, health and competence records for the contractor's workers is checked at the start of the work. A document requested later is not found after the job is done.
In Optifora
The contractor module keeps the firm, its workers, their documents and the area they will work in together; a site entry request with missing documents is flagged.