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There are two basic smoke detectors for sale in the U.S. – ionization smoke detectors and photo-electric smoke detectors. Ionization detectors use a minute amount of radioactive material to detect smoke particles while photo-electric detectors use a beam of light to detect the smoke particles. Ionization detectors are the most common and are relatively inexpensive, but tend to have more false alarms. Photo-electric detectors tend to have fewer false alarms, but are more expensive and sometimes are difficult to find in stores. Both detectors work differently and each detects a different type of fire more quickly than the other one (smoldering fire vs. a flash fire), but studies have shown that both are equally effective and normally sound an alarm within seconds of each other regardless of the type of fire.
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Most experts recommend you replace your smoke detector if it is ten years or older. One study conducted a few years ago found most smoke detectors do not work as reliably after ten years or so.
Without looking at your house it is virtually impossible to say exactly how many smoke detectors you need. We recommend smoke detectors should be in the hallway outside of bedrooms, inside the bedrooms and on every level of the floor. While this may seem like a lot of detectors keep in mind that the detector in the hallway outside the bedroom will most likely double as a detector on every level of the floor as well. If you have any questions call your local fire department.
Smoke detectors should either be installed on the ceiling or a few inches down from the ceiling on a wall. The reason smoke detectors should be installed a few inches lower than the ceiling is that smoke tends to curl when it reaches the 90 degree angle formed by the ceiling joining the wall and this forms a “dead space” where smoke may not penetrate.
Sometimes smoke detectors alarm for no apparent reason. In the summertime humid, wet weather will sometimes cause a detector to alarm (steam from a hot shower will also cause the alarm to sound). Another reason for an alarm might be due to someone cooking as food particles baked on to the oven can cause an alarm to sound. It is also possible that your detector is faulty. We recommend replacing your detector every ten years.
A number of manufacturers make smoke detectors now with lithium-powered batteries. These smoke detectors’ batteries supposedly last for ten years without being changed.
You should test your detector once every month by simply depressing the test button.
Most smoke detectors have a safety feature that causes the detector to chirp when the battery is low, but experts still say you should change the battery in your smoke detector at least once to twice a year (a good time to do this is when you change the clocks with the move to Daylight Savings Time) to be sure the batteries are good. The low-battery warning is a nice feature, but if the detector starts to chirp at 2 a.m. most home owners are not going to take the battery out and replace it at that time.
Disconnected or unplugged smoke detectors is the leading cause of inoperative smoke detectors in the United States. Instead of disconnecting the battery or electrical connection when the alarm sounds from a false alarm you may want to:
Carbon monoxide (CO) detectors are not currently required. However, we believe that carbon monoxide detectors are a good idea. Since carbon monoxide is colorless, odorless, tasteless and is known for mimicking the signs and symptoms of a person with a cold or flu, many people are exposed to CO without knowing it. Experts say at least one CO detector in a home is a good idea, especially if you live in a well-insulated home or there are young or old persons living in the home.
Carbon monoxide detectors should be placed in the hallway outside of the bedrooms. Since carbon monoxide filters throughout the air and does not rise like the smoke from a fire you can place your detector virtually anywhere on the ceiling or the wall (as long as it is a few inches down from the ceiling.)