Smoke detectors are designed to sense rising smoke in your home. They should be placed high on the walls of your home, but contrary to some beliefs, not necessarily on the ceiling. The reason being, from some in the fire extinguisher business, is that other deadly gasses, say from burning foam in couches, will actually rise to the top at ceiling level, forcing the smoke downward to possibly twelve inches below the ceiling. In this case, the smoke detector may not detect the smoke. It is better to place the detector around 12" from the ceiling on the wall.
Smoke detectors should be placed in bedrooms, kitchens away from stoves, living rooms, the top of stairways. Ultimately, every floor of your home should have at least one smoke detector in it. A smoke detector should also be placed in an attached garage.
Smoke detectors come battery operated and work independently, or they come with an electrical connection and have a battery backup supply. This way, when the power goes out, the smoke detector just keeps on protecting. These smoke detectors are called hardwired smoke detectors. They have an interconnecting wire that connects to each of the other smoke detectors in the home. That way, if on detector goes off, so do all the rest. This will warn you no matter where you may be in the home.
For safety purposes, always change the batteries twice a year. The easiest time to remember is when the time changes. The end of this month, the time changes and that's the perfect time to pitch the old batteries and replace them with fresh ones.
Most building codes today require hardwired smoke detectors be placed in homes, with the battery-powered type detectors be used as backup only. Most certainly if you're building a new home, you'll want to include the hardwired type for maximum safety. Learn how to wire a hard wired smoke detector.