The most commonly used smoke detector uses ionization detection, because it is the cheapest to manufacture. They are allowed by most housing codes and work just great for fast developing fires. However, they may not alert a sleeping child to a slow smoldering fire that can fill a room with deadly smoke before it goes off.

      The alternate choice is a photoelectronic smoke detector. It will detect smoldering fires, and could provide  as much as fifteen minutes of additional escape time.  The photoelectronic unit is also sold in a combination alarm, meaning it has both the ionization and the photoelectronic detector in one package. The duel detector is substantially more expensive, but by far a better choice over any single sensing detector.

      Smoke alarms do not detect flame, heat, or gas. They can only detect smoke ... if it can get to them. That's why most local codes now require that they be installed in each bedroom, adjoining hall ways to the bedrooms, on each level of the house and in the garage and basement.

    Smoke alarms initially relied on nine volt battery power, the same size batteries that are used in many toys and other household items. As a result, the batteries were often removed for other uses and the detector became useless. Now many building and housing codes require smoke detectors to be hard wired into a house circuit, with battery back-up. They can be wired so that they are all connected together. That way, if one detector goes off due to smoke, it will activate all the other alarms.