Smoke Detectors

Install Smoke Detectors Protect You and Your Family From Fire:

• When purchasing smoke detectors it is important to be sure that the detector has both ionization and photoelectric sensors.
• Note: If you have any fossil fuel burning appliances such as a gas furnace, a wood burning fireplace, or if you have an attached garage, be sure to get detectors with carbon monoxide sensors as well.
• Smoke detectors should be installed in every bedroom, in the hall outside of the bedrooms and one on each floor.
• All Detectors should be replaced every 10 years.
• Always follow manufacturer instructions when installing detectors
• Maintain your smoke detector.
• Develop and rehearse an escape plan so when your detector sounds, family members react appropriately.

Photoelectric Detectors:

• Occasionally, you will walk into a store and a bell will go off as you cross the threshold. If you look, you will often notice that a photo beam detector is being used. Near the door on one side of the store is a light (either a white light and a lens or a low-power laser), and on the other side is a photodetector that can “see” the light.
• When you cross the beam of light, you block it. The photodetector senses the lack of light and triggers a bell. You can imagine how this same type of sensor could act as a smoke detector. If it ever got smoky enough in the store to block the light beam sufficiently, the bell would go off.
• But there would have to be a lot of smoke before the alarm would go off — the smoke would have to be thick enough to completely block out the light. It takes quite a bit of smoke to do that. Photoelectric smoke detectors therefore use light in a different way. Inside the smoke detector there is a light and a sensor, but they are positioned at 90-degree angles to one another, In the normal case, the light from the light source on the left shoots straight across and misses the sensor. When smoke enters the chamber, however, the smoke particles scatter the light and some amount of light hits the sensor:  The sensor then sets off the horn in the smoke detector.
• Photoelectric detectors are better at sensing smoky fires, such as a smoldering mattress.
• Tests have found that smoldering fires, such as a mattress or a couch, photoelectric Detectors will go off between 15 and 60 minutes sooner than an ionization detector.

Ionization Detectors:

• Ionization smoke detectors use an ionization chamber and a source of ionizing radiation to detect smoke. This type of smoke detector is more common because it is inexpensive and better at detecting the smaller amounts of smoke produced by flaming fires.
• Inside an ionization detector is a small amount (perhaps 1/5000th of a gram) of americium-241. The radioactive element americium has a half-life of 432 years, and is a good source of alpha particles.
• Another way to talk about the amount of americium in the detector is to say that a typical detector contains 0.9 microcurie of americium-241. A curie is a unit of measure for nuclear material. If you are holding a curie of something in your hand, you are holding an amount of material that undergoes 37,000,000,000 nuclear transformations per second. Generally, that means that 37 billion atoms in the sample are decaying and emitting a particle of nuclear radiation (such as an alpha particle) per second. One gram of of the element radium generates approximately 1 curie of activity (Marie Curie, the woman after whom the curie is named, did much of her research using radium).
• Ionization detectors are better at sensing fast hot fires.
• Tests have found that fast hot moving fires, such as clothing, wood or drapery, ionization Detectors will go off between  30 and 90 second sooner than an photoelectric detector. While this might not seem like much time, it could be the difference between life and death.

Smart Detectors:

• Today there are smart detectors on the market such as Nest Protect, which cover the full spectrum of smoke and carbon monoxide detection. The Nest performs it’s own monthly test, has a night light if someone walks under it at night, and has the capability to send you a message on your cell phone alerting you of a fire or of high  carbon monoxide levels.

• Where you place smoke detectors depends on the size and layout of your home, and where people sleep in your home.
• Since the primary job of a smoke detector is to awaken sleeping persons and warn them of urgent danger, detector should be installed in bedrooms, outside of bedrooms, or other places where people frequently sleep. If two sleeping areas are separated, each should have its own detector. The hallway next to the bedrooms or other sleeping areas should be a priority location for detectors.
• Closed doors usually offer some protection against both fire and smoke from outside the room, however, they may make it more difficult to hear a detector alarm outside the bedroom. It is for this reason detector should also be installed in each bedroom.
• More significantly, they can keep smoke produced by a fire in a bedroom from reaching a detector in the hall.
• In single floor homes, the detector should be placed in the hallway near the bedrooms and in each bedroom. In a house where the bedrooms are upstairs, one detector should be near the top of the stairs to the bedroom area and in each bedroom.
• Detectors should also be installed on each level of the house. The basement ceiling, near the steps to the rest of the house, is another good location.
• Don’t put detectors within six inches of where walls and ceilings meet, or near heating and cooling ducts. Detectors located in these areas may not receive the flow of smoke required to activate the alarm.
• In homes with more than one sleeping area on the same level or on different levels, a smoke detector should be installed to protect each separate sleeping area and in each bedroom.
• Always follow manufacturer instructions when installing detectors

• Smoke detectors don’t need much attention. Regular testing and prompt replacement of batteries or bulbs is generally all that is needed.
• However, if you neglect these few requirements, your detector won’t do its job if a fire starts.
• Always follow manufacturer instructions for maintaining detectors.
• All Detectors should be replaced every 10 years.

• Always follow manufacturer instructions when testing detectors.
• At least once every month, test your detector by holding a candle six inches under it. If you’re testing an ionization detector, let the flame burn. To test a photoelectric unit, extinguish the candle and let visible smoke drift into the detector. Heavy tobacco smoke also will work. The unit’s alarm should begin to sound within twenty seconds. To stop the alarm, fan the smoke away from the detector. Soon the detector will become silent, and you can walk away knowing it’s still on guard.
• Using real smoke is more dependable than pressing the “test” button found on many older smoke detectors. In some older units, the button only starts the warning sound, and does not tell you whether the detector circuit itself is working. Some newer detectors have more refined test systems that simulate the presence of smoke in the chamber. These don’t need to be tested with real smoke. Check the package or instructions of your detector to see if it has this feature.
• All Detectors should be replaced every 10 years.

• Batteries will last approximately one year. If your battery-powered detector begins to emit its low-power warning sound, remove the weak battery and replace it immediately with a fresh one. Have a new battery on hand always.
• Although more expensive, lithium batteries have been proven to last much longer than alkaline batteries, and especially for detectors in high places lithium batteries should be considered.
• Replacement lamps for photoelectric detectors also should be kept on hand so no delay occurs in restoring their function. Owner neglect of testing and part replacement has been a cause of smoke detector failure, often resulting in tragedy.

• The detector is not a toy. Remind everyone in your family that it should not be operated, or even touched, except to test, maintain, and clean.
• Some authorities suggest using the detector test feature to operate the alarm as part of a family “fire drill” on occasion.
• Operating the alarm excessively draws heavily on battery power, and may cause a malfunction when it’s needed most.

• Do not respond to “nuisance” alarms (cooking, fireplaces, etc.) by disconnecting the battery. Either fan away the smoke or relocate the detector.

If It “Acts Up”:

• Most manufacturers back their detectors with a service or replacement warranty. If your detector begins to malfunction during the warranty period, follow the warranty procedure listed in the use and care literature. In some instances you can return the unit to the store from which it was bought. You may be instructed to send the unit directly to the manufacturer.
• Be sure to replace the detector.

When shopping for a smoke detector, consider these suggestions:

• Look for a laboratory seal of approval or a statement on the package or unit itself. A seal of approval indicates that the detector has been tested and certified by a recognized testing organization. Such a seal ensures that the unit meets certain standards of operation and sensitivity. The seal from Underwriter’s Laboratories (UL) is a common seal.
• Be certain that the detector has clear and detailed instructions that tell you how to install it, suggest where to place it, and provide directions for testing and maintenance.
• Be sure to check what type of detector and what kind of sensor it has.
• Depending on the situation, you may want to purchase a “wired” detector, or a “WIFI” detector that sends a radio signal to other detectors and sets them off in the event of a fire or carbon monoxide event.