Because one of the primary goals of a smoke detector is to alert people to a fire when sleeping, it is especially important to have smoke detectors installed outside or near each bedroom in a home. In homes with bedrooms located off a short hallway, one smoke detector will likely be sufficient. In longer hallways of more than 30 feet, place a detector every 30 feet. When bedrooms in a home are particularly spread out or on different levels, place a smoke detector outside each bedroom.
At least one smoke detector should be placed on each level of a home. Decades ago, the thought was that smoke detectors were only necessary outside of bedrooms and sleeping areas, but tests have shown that in many cases fires were able to grow to be too big to escape by the time smoke tripped the detector. In homes with an attached garage, a smoke detector should also be installed in the garage, even if another one is installed nearby in the home. It's also important to place smoke detectors at the top of stairwells because as the smoke from a fire rises the detector will be activated.
Although it's important to make sure your home is properly protected by smoke detectors, there are a few places where you should not install them. For example, a smoke detector should not be installed near wood stoves and fireplaces because false alarms are likely. And if you are installing one in the kitchen, make sure it is as far away from the cooking area as possible. Also, smoke detectors should not be installed on uninsulated exterior ceilings or walls because weather extremes can affect the batteries. Installing them near doors and windows can also cause problems if the area is drafty.