Smoke alarms, photo-electric vs ionisation.?

Just a blonde question. If new homes are fitted with photo-electric hard wired alarms. where do they get there power from? Sure there is the battery back up... but that isn't what i'm questioning. Is the power supply part of the main power. or is it a separate black out proof option?

Public Comments

1. Ok Blondie the question sounds ok to me. Yes the hardwired smoke detectors are run on a dedicated circuit from your main electrical panel. Some have battery back ups and some don't. Unfortunately there is no such thing as a black out proof option when it comes to household electricity. If you are concerned about fire then you can also pick up a battery smoke detector and put it where you are worried about. As long as you change the battery ( 9 volt) once a year and the whole thing about every 10 years you will have good protection. As far as photo electric vs ionization is concerned both are excellent devices. The photo electric is a bit faster detecting a smouldering fire with large smoke particles while the ionization is better for fast moving fire but the difference is minimal. If you are really concerned get one on each or you can now buy ones with both types Incorporated into one smoke detector
2. This is actually a GREAT question! Most home owners--new or not--are totally unaware of this issue surrounding hard-wired smoke alarms. Most hard wired alarms are not equipped with batter back up systems. If yours is, that's a nicer system than most recieve. The wiring and electrical supply for these IS hooked into your electrical system and therefore, when your power is OUT, so is your system! Builders usually install these because of code requirements that specify that newer buildings have "permanent" smoke detection systems. Battery opperated units do not qualify as batteries rapidly lose their energy supply. I value the hard-wired alarms as an extra "back-up" to my battery opperated units since they are useless in an electrical fire or a fire that occurs when your power is out.
3. I have to disagree with ec 1177. Photoelectric-type smoke alarms are much much better than Ionization-types. Ionization-types are just a little better for smoke from flaming fires. I have done scores of tests to compare these two types. I disagree also with Handy Mam about the value of adding batteries to AC operated units. This may be an advantage for some very conscientious individuals, but not for the average person. When the batteries in these units wear out, a trouble signal sounds. At best the owner will take the detector down, and replace the battery promptly. At worst ( and I have found them this way) the detector comes down and doesn't go back for days, if at all. It is not good to have a smoke alarm which is AC operated only. It is less good to have one which may not stay in service at all. It is not a good vs. bad situation, but a choice which determines the least bad.