Interconnected alarms: what happens when one head fails the test

In buildings with interconnected smoke alarms, one dead head raises a fair question: does the system pass because the rest sound, or fail on the one that does not? The NSPIRE standard is written per alarm — each required alarm must be present and operable — so a single inoperable unit is recorded on its own, whatever the rest of the string does. The practical trap is testing only from one button and assuming the string proves every head. Test each alarm at its own location, note the expiration date while you are on the ladder, and replace a failed head the same visit. How does your team test interconnected strings? — Admin