Types of Smoke Alarms and Detectors

Heat Detector

According to the National Fire Protection Association (NFPA), approximately two-thirds of U.S. household fire deaths result from fires in homes with no smoke alarms or with working smoke alarms with old or missing batteries.

Whether it’s a household setting or in a business, the selection and maintenance of an early warning system is critical to save lives and minimize property loss.

Smoke alarms should be placed on each level of your home and outside of each sleeping area. If bedroom doors are closed, additional alarms should be located inside the bedrooms, as well. Since smoke rises, the installation should be on the ceiling at least four inches away from the nearest wall and away from drafts from windows or air ducts.

There are two broad types of fire alarm systems; heat detectors and smoke alarms. Knowing the differences between the various types of fire alarms available is key to matching the appropriate product to the application.

Heat DetectorsHeat Detector
  • Heat detectors are the oldest type of automatic fire detection device. Heat detectors feature a detecting element inside the unit that activates when it reaches a predetermined fixed temperature or when a specific increase in temperature has occurred.
  • Heat detectors are best suited for applications where detection speed is not a prime consideration or where ambient conditions would not allow the use of a smoke detector, for fire detection in small, confined spaces where rapidly burning, high heat fires are anticipated
  • Heat detectors have a lower false alarm rate, but they are also slower than smoke detectors in detecting fires.
Smoke Alarms
  • Smoke AlarmSmoke alarms will detect most fires more rapidly than heat detectors. There are currently three types of smoke alarms on the market: ionization, photoelectric and combination ionization/photoelectric.
  • An ionization smoke alarm contains a small amount of radioactive material. The radiation passes through an ionization chamber which is an air-filled space between two electrodes and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm.
  • Photoelectric smoke alarms operate using a light source, a light beam collimating system and a photoelectric sensor. When smoke enters the optical chamber and crosses the path of the light beam, some light is scattered by the smoke particles, directing it at the sensor and thus activating the alarm.
  • Combination smoke alarms feature both ionization and photoelectric technologies. Ionization smoke alarms respond faster to high energy fires, whereas photoelectric detectors respond better to low energy smoldering fires. The NFPA recommends using both smoke alarms in the home for the best protection.

Smoke alarms vary in how they are powered. 9 volt battery powered smoke alarms are very popular due to their low cost, however, care must be taken to replace the battery on a regular basis.

Smoke alarms are also available in 120 volt and a long life 10 year rated lithium battery. Many local or state building codes may require 120 volt interconnected smoke alarms with a battery back-up in case of power outages. The interconnected feature allows all smoke alarms to be linked together. This is especially important in multi-levels homes or in apartment buildings. Smoke alarms with high intensity strobe lights are also available for the hearing impaired.

Regardless of the type of detector or alarm selected, the proper placement and maintenance of the device is crucial. The NFPA suggests battery replacement at least once a year on battery equipped units and a monthly detector test to verify the alarm function. Many people utilize daylight saving time in the spring and the fall as a reminder to change batteries.

 

If you want more information on our safety training or consulting contact Randy Free. 407-353-8165 or email him at rfree[at]safetylinks.net

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