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There is no doubt that smoke alarms have saved countless lives. Having the best detectors and installation should never be
compromised for the safety of you and your family. How many times have you listened to a news report about someone dying in
a house fire and it was reported that there were no working smoke detectors in the home?

Here are some guidelines on smoke alarms I hope will help you in deciding how these should be installed in your home.

Types of Detectors

Ionization - These are the most common type of detectors I see in the homes I inspect. Mainly for the reason that these are the
least expensive detectors to purchase. Ionization detectors contain radioactive material that ionizes the air,making an electrical
path. When smoke enters, the smoke molecules attach themselves to the ions. The change in electric current flow triggers the
alarm. The radioactive material is called americium, is a radioactive metallic element produced by bombardment of plutonium
with high-energy neutrons. The amount is very small and not considered harmful. These detectors are better at detecting flaming

Photoelectric - This type of detectors contain a light source (usually a bulb) and a photocell, which is activated by light. Light
from the bulb reflects off the smoke particles and is directed towards the photocell. The photocell then is activated to trigger the
alarm. These cost more to purchase and are better at detecting smoldering fires.

Combination Ionization and Photoelectric - These cost more than photoelectric detectors but provide a higher level of
protection since they will detect flaming or smoldering fires more accurately.

Combination Carbon Monoxide (CO) and Smoke Detectors - These detectors are available in both ionization and
photoelectric smoke and fire detection as well as carbon monoxide detection.

Proper Installation

Proper installation of detectors is very important so they operate as intended. Avoid installing detectors near fireplaces and
wood stoves to avoid false alarms. Install smoke detectors at the top of each stairwell and at the end of each long hallway.
Smoke rises easily through stairwells. If you should put a smoke detector in your kitchen, be sure to keep it away from cooking
fumes or smoking areas.
Proper mounting of a smoke detector also is important. You can mount many detectors by yourself, but those connected to your
household wiring should have their own separate circuit and be installed by a professional electrician. If you mount your detector
on the ceiling, be sure to keep it at least 18 inches away from dead air space near corners. If you mount it on the wall, place it
four to 12 inches below the ceiling and away from corners. Keep them high because smoke rises.
Never place them any closer than three feet from an air register or return vent that might re-circulate smoke.
Do not place them near doorways or windows where drafts could impair the detector operation.
Do not place them on an uninsulated exterior wall or ceiling. Temperature extremes can affect the batteries.
Do always remove them if the area is undergoing painting with a paint sprayer so it does not become disabled with paint
coating the electronics and sensors.
Most jurisdictions now require detectors for new construction to be hardwired to the home's electrical system and
interconnected so if one sounds, all detectors in the home sound. Most detector manufactures now offer battery only detectors
that are wireless interconnected.


Of course changing the batteries in the detectors are the number one priority. If the detectors are battery only operated, you will
have no protection if the batteries die. Hardwired detectors will operate as long as the home's electrical system is operating but
a fire can cause the electrical circuit to trip and electricity can go out during a storm so be sure to change batteries twice a year.
The easiest way to remember to change your batteries is to do this when daylight savings time changes.
Test your detectors. After changing the batteries, test the detectors by pressing the test button or let smoke rise into the
Detectors should also be completely replaced every 10 years. Although the detector may alarm when tested, it is
recommended to change it after the 10 year period. The manufacture date of the unit should be labeled on the back.

Smoke Detectors and Installation

Fort Worth & Dallas Texas Home Inspector Providing The Very Best Home Inspections

Kent Keith, LLC