Section 907 sets when a fire alarm and detection system is required, and the trigger is usually occupancy plus occupant load. Many Business, Assembly, Educational, and Residential occupancies require a manual and/or automatic alarm once they pass a threshold number of occupants or stories; the specifics live in 907.2, group by group.
Where a system is required, it has to provide occupant notification — audible and visible appliances meeting NFPA 72 — and it typically integrates with sprinkler waterflow so a flowing head signals the alarm.
A common mistake is assuming sprinklers alone satisfy 907, or providing initiation without full notification-appliance coverage. Reviewers confirm the 907 trigger for the specific occupancy and that the alarm scope on the plans covers both initiation and notification, not just one.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.