Who should be immediately notified of unplanned removal from service?

The correct choice is to notify the building owner of an unplanned removal from service. This is crucial because the building owner has the ultimate responsibility for the safety and compliance of the property. The owner's awareness of the situation enables them to take appropriate action, such as arranging for repairs or implementing alternative fire protection measures while the sprinkler system is down.

Notifying the owner immediately ensures that they can inform occupants about potential hazards and take necessary steps to mitigate risks. The owner may also need to communicate with insurance providers or local authorities to maintain compliance with regulations regarding building safety and fire protection. Prompt notification is essential not just for compliance, but also for ensuring the safety of individuals within the building.