The majority of fires that kill people happen at night. If you're asleep, the smell of smoke won't always wake you up. In fact, smoke and poisonous gases can put you into a deeper sleep. Inexpensive smoke alarms can wake you in time to escape, greatly increasing your chances of survival. How to choose an alarm.
Some home alarms run on batteries, others on household current.
There are also different sensor technologies, some faster to react when fires are smoldering, others faster when fires are openly flaming, ALL are fast enough to provide sufficient warning. All laboratory tested smoke alarms, regardless of type, will protect you if they're installed and maintained properly. Install at least one smoke alarm on every floor of your home, including the basement and outside each sleeping area. Smoke alarms should also be installed in sleeping rooms, especially if you sleep with the doors closed. New home construction now require hard wired smoke detectors in each sleeping room in addition to each level of the home.