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Smoke Detectors
Overview
Smoke detectors are devices that are mounted on the wall or ceiling and automatically sound a warning when they sense smoke or other products of combustion. When people are warned early enough about a fire, they can escape before it spreads. Prices start at about $6 and up.

Although we like to feel safe at home, about two-thirds of our nation's fire deaths happen in the victim's own home. The home is where we are at the greatest risk and where we must take the most precautions.

A John Hopkins University study, funded by the United State Fire Administration, found that 75 percent of residential fire deaths and 84 percent of residential fire injuries could have been prevented by smoke detectors.

Topics

Death By Fire 
Six thousand Americans die every year in residential fires. Most of these deaths are not from heat or flames but from inhaling smoke and toxic fumes.

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Buying Time 
When a smoke detector detects smoke, an alarm automatically sounds. Most fatal home fires occur between 8:00 at night and 8:00 in the morning. Fire often generate lethal amounts of unseen smoke and fumes well before flames are visible and before heat make resident feel uncomfortably warm. Many people who died in home fires were asleep and never woke up. When installed and maintained smoke detectors can prevent such needless deaths. Smoke detectors buy time to get out of the house fast - before toxic fumes accumulate to lethal levels. 

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Which Type
IonizationIonization
Contains a small amount of radioactivity that conducts electricity. Electric current flows continuously between two electrodes in the chamber. When smoke particles enter, they disturb this flow, causing the alarm to go off.

PhotoelectricPhotoelectric
Contains a beam of light and a photocell within the chamber. When smoke enters, it deflects the beam, causing it to strike the photocell and set off the alarm.

Which is Better?
Ionization detectors are more sensitive to the tiny particles of combustion that can't be seen or smelled - these emitted by flaming fires. Photoelectric detectors are more sensitive to the large particles of combustion emitted by smoldering fires. Consequently, ionization detectors will respond faster to flaming fires, and photoelectric detectors faster to smoldering fires.

The differences between the two types are generally not critical, since the difference in response time is only a matter of a few seconds. Since most hose fires produce a rich mixture of smoke types, with detectable amounts of both large particle and small particle smoke early in the fire's growth, either an ionization or a photoelectric detector will meet most needs. 

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Placement
Buy as many smoke detectors as it take to give your home complete coverage.
  • You obviously increase your chances of survival with each one that you have, but one each level of the house is the absolute minimum.
  • You should have a smoke detector in each bedroom and the door should be closed when the occupant is asleep.
  • You should have one in the hallway outside the bedroom area.

Single Level
Single level layout

Multi-Story 
Multi story layout

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Installation 
  1. Follow the manufacturer's installation instructions. 
  2. On the ceilings, mount the device away from corners and walls, which have dead air space nearby. About twelve inches is the recommended distance. 
  3. On walls, install the detectors high, because smoke rises, and place them twelve inches away from corners and ceiling
    Installation
  4. Install smoke detectors at least three feet from vents and ceiling fans which might re-circulate the smoke. 
  5. Never place smoke detectors on un-insulated interior and exterior walls or ceilings, the difference in temperature between the interior and exterior can ruin batteries and prevent smoke from reaching the detectors.

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City of Kerrville
701 Main Street
Kerrville, TX 78028
830-257-8000