The answer to 'what size smoke detector do I need' is that the size of smoke detector you need depends on the size of the room or area you are trying to protect. Most standard residential smoke detectors are designed to cover a 30-foot to 50-foot diameter area. For smaller rooms like bedrooms, a 6-inch diameter smoke detector is typically sufficient. For larger open areas like living rooms or hallways, an 8-inch to 10-inch diameter smoke detector is recommended to ensure full coverage.
It's important to install smoke detectors on every level of your home, including the basement and attic, and within 15 feet of each bedroom door. Properly spacing and installing the right size smoke detectors will help ensure your home is protected in the event of a fire.