Smoke detector

• A smoke detector is a device that detects smoke and issues an alarm to alert nearby people that there is a potential fire . 
• A household smoke detector will typically be mounted in a disk-shaped plastic enclosure about 150mm in diameter and 25mm thick . 
• Because smoke rises , most detectors are mounted on the ceiling or on a wall near the ceiling and , to avoid to nuisance of false alarms , are mounted away from kitchens .