Ordinary smoke alarms can only do this one thing
Protecting your home from fire is important, and smoke detectors perform a vital role in keeping your family safe. However, smoke detectors have various shortcomings. For instance, they are only able to detect smoke, not high temps. In the event there is an emergency in your house, you might not be warned before the smoke reaches the smoke detector. While there are additional unmistakable indications of fire -- including a marked increase in warmth -- if there's no smoke, you will fail to get a sounding of your smoke detector.
What’s more, smoke detectors only beep when they detect enough smoke. When a fire starts small, you may not be cautioned until it's too late. Many smoke detectors employ dual-sensor technology, meaning they will detect smoke from both a blazing inferno and something less intense. Whenever they sound their alarm, it's up to the occupant to contact the fire department after safely leaving the residence.