If you utilize stand-alone smoke detectors (those that are just mounted on the wall), you must be in the house in order to hear the alarm. Even then, you may not hear it if you are in a deep sleep. Unfortunately, sellers of such alarms do not caution you about that.
But what if you are not home—on vacation, or even out for a short errand.
To be protected at all times, you must have a system that is monitored by a central office.
Check with your insurance carrier to see if a central office monitored system is required for you to qualify for a reduced rate.
DO NOT DELAY!