Alarms assist operator, rather than confusing or overwhelming them

There is rarely any mistake about what a fire alarm means

Due to training, most citizens immediately evacuate without even thinking

Only required information conveyed
Must address the operator using an interface that is convenient, or operator may miss/ignore them

Loud sound combined with flashing lights, almost universally recognized as emergency

Sound loud enough to capture attention of everyone

Location based event, so location based alarm makes sense
Must not trigger unnecessarily, or the operater may become conditioned to ignoring them

Though false alarms occur, they are usually rare enough that the users do not become conditioned to them