Traditional smoke alarms can only do one thing
Defending against fire is a crucial consideration, and smoke detectors perform a critical part in keeping your family safe. Even so, smoke detectors have some limitations. To illustrate, they will only react to smoke, not extreme temperatures. If there is an emergency in your home, you would not be alerted before the smoke ascends to the smoke detector. While there are additional telltale indications of fire -- like a marked heat increase -- if there's no smoke, you will fail to get a warning from your smoke detector.
Additionally, smoke detectors only sound the alarm when they detect ample smoke. In the event a fire creeps along slowly at first, you may not be cautioned until the situation is out of hand. Some smoke detectors employ dual sensors, meaning they will detect smoke from both a blazing inferno and smoldering remnants. If they do go off, it's up to the occupant to contact the fire department after they safely leave the residence.