The best smoke detector is the human nose but that is only true if the person is alert, awake, and responsible. Since this is not the case 24 hours a day, a reliable automatic system should be used.
Detectors are good early warning devices , providing more time to get out in the event of a fire.
Both heat and smoke detectors are available and you should have some of each type. Test the devices frequently and make sure battery operated detectors have new batteries installed at least once a year. Never place a detector in front of a wall or ceiling air duct outlet. Make sure they are installed properly and that you have one on every level of you home, including your basement and attic. Even more detectors should be installed if you have a large home.