Here is some information on where to install smoke detectors. Some local codes may vary, so check first.
 Wall-mounted units should be mounted so that the top of the detector is 4 to 12 inches from the ceiling. A ceiling-mounted detector should be attached at least four inches from the nearest wall. In a room with a pitched ceiling, mount the detector at or near the ceiling's highest point. Place the detector near the bedrooms, within 15 feet of sleeping areas. The National Fire Alarm Code, developed by NFPA, requires a smoke detector in each sleeping room for new construction. it is a good idea to place one on each level of the house. Also additional detectors can be installed near the furnace and washer and dryer. Because smoke rises, mount detectors high on a wall or on the ceiling. Place them in an area away from air vents The basement ceiling near the steps to the first level is a good location. But don't install the detector at the top of the basement stairs where there is a closed door, dead air space near the door may prevent smoke from reaching the detector.
 There is more to checking a smoke detector than just pushing the test button. Dust and even small insects can sometimes block a photoeye type or ionization type of smoke detector. They also should be cleaned periodically. Dont go to long before changing batteries. If they are hard wired make sure they have a battery back up. Smoke detectors should not be taken lightly. They could save your life.