Traditional smoke alarms can only do this one thing
Protecting your home from fire is important, and smoke detectors play a critical part in safeguarding your family. However, smoke detectors have their limitations. For example, they will only react to smoke, not heat. If there is a blaze starting in your house, you may not be cautioned unless the smoke ascends to the smoke detector. While there are some other significant signals of fire -- like a marked heat increase -- if there’s a lack of smoke, you will fail to get a triggered smoke detector.
What’s more, smoke detectors only beep if they encounter enough smoke. When a fire creeps along slowly at first, you may not be alerted until the situation is out of hand. Some smoke detectors employ more than one sensor, which means they will detect smoke from both a raging fire and something less intense. Then when they sound their alarm, it falls to the resident to contact first responders after exiting the premises.