Keep it subtle but undeniable. This creates curiosity or initial concern for your characters (or incident responders).

Don't just rely on text. Use flashing lights, specific alarm frequencies, or physical vibrations to ground the reader in the environment.

This is the first signal that something is wrong. It shouldn't reveal the whole picture, but it should disrupt the normal routine or baseline operations.

Five minutes later, the automated fire suppression system reports a sudden spike in ambient temperature, or data loss prevention software flags an massive, unauthorized file transfer. 3. The Climax (Alert 3: The Critical Point)

A motion sensor trips in a restricted server room, or a security dashboard flags a single anomalous login from a remote location. 2. The Rising Tension (Alert 2: The Complication)