Smoke and CO2 Alarms

I have the latest version of First Alert Z Wave smoke and co2 detectors. The issue is that when one unit senses smoke, the other units do not sound. This feature is actually required by law in many states, including mine (so I have now purchases a second set of detectors to meet code). Because everything is connected via z wave, it seems very straightforward to tell all the smoke detectors to sound if one of the units senses smoke. The base station is already sounding, the monitoring company has already been contacted, and my phone has already been alerted; why not the other units? If someone was sleeping at the other end of the house, they might not get any of the messages and they could easily be in trouble quickly.