Understanding different types of smoke detectors

Reviewers agree on one thing: The best smoke alarms can sense both types of fires (flaming and smoldering) with equal effectiveness, and that means either buying a smoke detector with both an ionization sensor for flames and a photoelectric sensor for smoke, or using two separate smoke alarms to achieve the highest degree of safety and preparedness.

Reviews show that smoke detectors equipped with just a single sensor are not nearly as effective as those with dual sensors. Ionization models are very good at signaling the presence of a fire with high flames but are much slower to detect smoky blazes. Conversely, photoelectric smoke alarms are much more effective at detecting smoky fires but do not fare as well in high-flame fires. Flaming fires are often fueled by paper or flammable liquids and often include kitchen fires. Smoldering fires are often fueled by bedding, clothing and upholstery.

Ionization smoke detectors use a harmless radioactive source that establishes an electric current in the detector chamber; when smoke enters the chamber, the unit senses the change in electrical current and triggers the alarm. Photoelectric smoke alarms activate when the smoke is dense enough to deflect a beam of light. The best smoke detectors, reviews say, employ a combination ionization/photoelectric sensor that can detect both flaming and smoldering fires with equal speed and accuracy. This is no small matter: Smoke detectors are meant to save lives and protect your home, and experts say they improve your chances of surviving a fire by 50 percent.

Experts say you should consider the following when choosing a smoke detector:

  • Choose a smoke detector that uses a combination ionization/photoelectric sensor and is able to detect both flaming fires and slow, smoldering fires with equal speed and accuracy. If you choose not to use a dual-sensor model, you'll need both ionization and photoelectric smoke detectors installed in your home.
  • Only consider a smoke alarm that meets Underwriters Laboratory (UL) standards. UL is a safety certification organization that evaluates products and makes sure they comply with safety regulations. Most smoke detectors -- but not all -- meet UL standards. The manufacturer will disclose either on the model's packaging or within its manual whether the unit meets the UL standards.  
  • Smoke detectors should have a test button to ensure that alarms and sensors are operating correctly. If you don't feel like climbing up on a chair or ladder to test the alarm, look for a smoke detector with a test button that can be activated with a television remote. Alarms should be tested on a monthly basis to ensure that the electronics and battery are functioning properly.
  • Make sure the smoke alarm has a hinged or removable cover for easy cleaning. Too much dust can cause a sensor to fail. Most smoke alarms can be vacuumed to prevent dust buildup.
  • Check that the smoke detector has a feature that allows you to silence false alarms. This can help avoid the temptation to disable the unit.

Smoke detectors have a lifespan of about seven to 10 years, and it's important to replace old detectors according to the model's recommendations. Smoke alarms that use nine-volt and AAA batteries should get fresh batteries at least once a year. Experts suggest replacing the batteries when you change your clocks each year for the start of Daylight Saving Time. Other maintenance includes a monthly testing of the alarm and cleaning with a vacuum hose about once every month.

Experts recommend a smoke detector on each floor of your home and outside each bedroom, or inside the bedroom if you sleep with the door closed.

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