Smoke is very deadly. Rather than awakening you, it will put you into a deeper sleep! Most fire deaths occur at night and are due to smoke inhalation, not fire. Typically, the victims are still in their beds, having never been aroused from their sleep.
To wake up and survive a nighttime fire, you must have a working smoke detector!
One detector outside each sleeping area
One detector on each level of your home
An additional detector in each bedroom
You could be overcome by smoke before any detectors in the hallway sound the alarm, or if the fire starts in the hallway and you sleep with your door closed, the alarm may not wake you.
Check at least once a month by pushing the test button.
Clean periodically by removing the cover and dusting or vacuuming (in accordance with manufacturer recommendations).
Change the battery at least once a year.
A periodic "beep" or "chirp" means that your battery is low and needs to be replaced immediately. Don't disconnect the battery until you have one to replace it.
Follow the manufacturer's instructions. If none are available, consider these guidelines:
Mount on the ceiling or up high on the wall, but keep detectors about four inches away from the corner where the ceiling and wall meet (the corner is a "dead air space" where the detector won't be in the path of smoke travel).
For high pitched or "cathedral" ceilings, mount the detectors three feet from the highest point.
Avoid placement in the path of A/C or heater vents.