Replies

1. 
   DanH | Oct 15, 2012 07:09am | #1

   Generally what you want are "smoke alarms", not "fire alarms" -- they sense smoke, not heat.  (By the time a heat sensor goes off it's too late.)

   Smoke alarms are available in a wide variety of styles, but there are just a few major variations--

   • First off, an alarm can be battery powered, line powered, or line powered with battery backup.

   • Alarms can be interconnected so that if one goes off they all go off.  Used to be that you needed to have them on a single common 3-wire cable for this function, but I would guess that by now there are some that use RF signals of some sort and only need to be connected to any AC circuit.

   • Alarms can be smoke-only or combo smoke/CO2.  CO2 detectors are not needed in every detector location, just near "combustion appliances" -- furnaces, gas water heaters, gas ranges, fireplaces, etc, but there should be at least one in any house, even an all-electric one.  And it's wise to have one near any entrance from an attached garage.

   • Smoke alarms can be "ionization", "photoelectric", or both.  Generally, "photoelectric" better, but it's pretty hard to find photoelectric alarms any more, and they're apt to be pretty expensive.

   • And of course, the cheaper detectors, while certified to be as reliable as the expensive ones, are often ugly as sin -- you may have to shop around and pay a little more to get nice looking ones.

   You can read on the web where they should be installed, but generally:

   • Just outside any utility room.

   • Just outside the kitchen.

   • Just outside any bedroom.

   • Don't place too close to fireplaces, etc, as they will be subject to false alarms.  Similarly, units in a kitchen, in addition to collecting grease, may give false alarms due to cooking.

   Smoke detectors should be installed on or within a few inches of the ceiling.  CO2-only detectors can be installed at any height.