Traditional smoke alarms will only do this one thing
Fire safety is important, and smoke detectors play a critical role in keeping your family safe. Despite that fact, smoke detectors have their shortcomings. For instance, they are only able to identify smoke, not extreme temperatures. When there is a blaze starting in your house, you may not be warned before the smoke reaches the smoke detector. Although there are further telltale signs of fire -- like a marked heat increase -- if there's no smoke, you won’t have a triggered smoke detector.
Additionally, smoke detectors only sound the alarm if they encounter enough smoke. When a fire creeps along slowly at first, you may not be warned until the flames are out of control. Some smoke detectors employ dual sensors, meaning they will recognize smoke from both roaring flames and something less intense. If they do go off, it falls to the resident to contact first responders after they safely leave the premises.