Why Install Smoke Alarms?                   
Smoke alarms are a powerful and effective fire safety device.  They are the first lines of defense against smoke and fire.  They may awaken those who would otherwise have been overcome by smoke and toxic gases in their sleep.  And most importantly, they provide an early warning alerting individuals of a fire, allowing them precious time to escape.
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 According to the National Fire Protection Association (NFPA), 75 to 80% of all deaths by fire happen in the home.  More than half of these deaths occurred in buildings without functioning smoke alarms.  By installing a smoke alarm, individuals can reduce the risk of dying in a fire almost 50%.
                                                                  

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Smoke Alarm Technology
Not all fires are the same. There are two basic types of smoke alarms in use today: ionization and photoelectric -- that detect two different types of fire.. The sensing chambers of these alarms use different principles of operation to sense the visible or invisible particles of combustion given off in developing fires.

Ionization Smoke Alarms 
Ionization smoke alarms generally respond first to fast flaming fires. A flaming fire devours combustibles extremely fast, spreads rapidly and generates considerable heat with little smoke.

Ionization models are best suited for rooms which contain highly combustible materials, These types of materials include:
- cooking fat/grease
- flammable liquids
- newspapers
- paint
- cleaning solutions

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How Ionization Alarms Work
A typical ionization chamber consists of two electrically charged plates and a radioactive source, (typically Americium 241) for ionizing the air between the plates, (See Figure 3-1). The radioactive source emits particles that collide with the air molecules and dislodge their electrons. As molecules lose electrons, they become positively charged ions. As other molecules gain electrons, they become negatively charged ions. Equal numbers of positive and negative ions are created. The positively charged ions are attracted to the negatively charged electrical plate, while the negative charged ions are attracted to the positively charged plate, (See Figure 3-2). This creates a small ionization current that can be measured by electronic circuitry connected to the plates.
       

Particles of combustion are much larger than the ionized air molecules. As particles of combustion enter an ionization chamber, ionized air molecules collide and combine with them, (See Figure 3-3). Some particles become positively charged and some become negatively charged. As these relatively large particles continue to combine with many other ions, they become re-combination centers, and the total number of ionized particles in the chamber is reduced. This reduction in the ionized particles results in a decrease in the chamber current that is sensed by electronic circuitry monitoring the chamber. When the current is reduced by a predetermined amount, a threshold is crossed and an alarm condition is established.
                           

Changes in humidity and atmospheric pressure could affect the chamber current and create an effect similar to the effect of combustion particles entering the sensing chamber. To compensate for the possible effects of humidity and pressure changes, the dual ionization chamber was developed and has become commonplace in the smoke alarm market.

A dual-chamber alarm utilizes two ionization chambers: one is a sensing chamber that is open to the outside air. (See Figure 3-4). Particulate matter, humidity, and atmospheric pressure affect the sensing chamber. The other is a reference chamber that is partially closed to outside air and affected only by humidity and atmospheric pressure, because its tiny openings effectively block the entry of larger particulate matter such as smoke. Electronic circuitry monitors both chambers and compares the outputs. If the humidity of the atmospheric pressure changes, both chambers’ outputs are affected equally and cancel each other out. When combustion particles enter the sensing chamber, its current decreases while the current of the reference chamber remains virtually unchanged. The resulting current imbalance is detected by the electronic circuitry, (See Figure, 3-5).
             
                                      

There are a number of problems that can affect dual-chamber ionization sensors; dust, excessive humidity (condensation), significant air currents, and tiny insects can be misread as particles of combustion by the electronic circuitry monitoring the sensors. The more sensitive the alarm calibration, the more likely it is that these problems will affect the alarm performance and result in nuisance alarms.

FOR BEST HOME PROTECTION INSTALL AT LEAST ONE PHOTOELECTRIC AND ONE IONIZATION SMOKE ALARM ON EACH LEVEL OF YOUR HOME.

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Photoelectric Smoke Alarms 
Photoelectric alarms generally respond first to slow smoldering fires. A smoldering fire generates large amounts of thick, black smoke with little heat and may smolder for hours before bursting into flames.

Photoelectric models are best suited for living rooms, bedrooms and kitchens. This is because these rooms often contain large pieces of furniture, such as sofas, chairs, mattresses, counter tops, etc., which will burn slowly and create more smoldering smoke than flames. Photoelectric smoke alarms are also less prone to nuisance alarms in the kitchen area than ionization smoke alarms.

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How Photoelectric Smoke Alarms Work

Photoelectric Light Obscuration Smoke Alarm
One basic type of photoelectric alarm, the light obscuration alarm, employs a light source, and a photosensitive receiving device (such as a photo-diode), (See Figure 3-6). When smoke particles partially block the light beam (See Figure 3-7), the reduction in light reaching the photosensitive device alters its output. The change in output is sensed by the alarm’s circuitry, and when the threshold is crossed an alarm is initiated. Obscuration Type alarms is usually of the projected beam type where the light source expands the area to be projected. (i.e., atrium).
                  

                 

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Photoelectric Light Scattering Smoke Alarm
Most photoelectric smoke alarms are of the spot type and operate on the light-scattering principle. A light-emitting diode (LED) is beamed into an area not normally “seen” by a photosensitive element, generally a photo-diode, (See Figure 3-8). When smoke particles enter the light path, light strikes the particles (Figure 3-9) and is reflected and/or refracted onto the photosensitive device causing the alarm to respond.

  

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Smoke Alarm Design Considerations
Smoke alarms are based on simple concepts, but certain design considerations need to be observed. They should produce an alarm signal when smoke is detected, but should minimize the impact of an unwanted signal which can arise from a variety of causes: In an ionization alarm, dust and dirt can accumulate on the radioactive source and cause it to become more sensitive. In a photoelectric alarm, light from the light source may be reflected off the walls of the sensing chamber and be seen by the photosensitive device when no smoke is present; the entrance of insects, dirt, drywall dust, and other forms of contamination into the sensing chamber can also reflect light from the light source onto the photosensitive device.

Underwriters’ Laboratories, Inc. established the allowable sensitivity ranges for both types of alarms and all are verified by their performance in fire tests. Regardless of their principle of operation, all smoke alarms are required to respond to the same test fires.

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Choosing a Smoke Alarm
The following features should be considered when choosing a smoke alarm to best suit your needs:

Alarm Silencer feature will silence an alarming unit for several minutes, giving the air time to clear.  These models are ideal near kitchen and cooking areas where most nuisance alarms occur.

Press and hold center of cover for up to 20 seconds to activate Easy Touch™ Alarm-Pause®. Alarm will beep for up to 10 seconds to indicate activation.

Note:  Consumers should always determine the reason for the unit sounding before quickly dismissing it as a nuisance alarm by pressing the Alarm Silencer button to silence the alarm.

A built-in emergency light (SA358)that will turn on when the unit goes into alarm.  The emergency light will illuminate an escape route in case of a power failure.  These units are best utilized when installed by stairs and in hallways.

Long Life smoke alarms (SA900, 300AP) utilize lithium batteries that provide up to 10 years of continuous protection.  Lithium batteries eliminate the need and expense of annual battery replacement.  When Long Life smoke alarms near the end of their useful life, they will sound a low battery signal to remind consumers to replace the entire unit.

The NFPA reports that 1/3 of all smoke alarms installed in homes are not operating because of dead or missing batteries.  This is an all too common occurrence in smoke alarms that leaves families and homes vulnerable.

Note:  it is recommended that smoke alarms be replaced every 10 years and be tested regularly.

Hardwire smoke alarms (SA360, SA379, ASD100, ESA5011, COS2010)are connected to a home’s AC power supply and should be installed by a licensed electrician according to the local electrical code. AC power means you never have to replace a battery to protect your home and family.

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Considerations in Selecting a Smoke Alarm
The characteristics of an ionization alarm make it more suitable for detection of fast flaming fires that are characterized by combustion particles in the 0.01 to 0.3-micron size range. Photoelectric smoke alarms are better suited to detect slow smoldering fires that are characterized by particulates in the -.3 to10.0 micron size range. Each type of alarm can detect both types of fires, but their respective response times will vary, depending on the type of fire.

Because the protected buildings normally contain a variety of combustibles, it is often very difficult to predict what size particulate matter a developing fire will produce. The fact that different ignition sources can have different effects on a given combustible further complicates the selection. Alighted cigarette, for example, will usually produce a slow smoldering fire if it is dropped on a sofa or bed. However, if the cigarette happens to fall upon a newspaper on top of a sofa or bed, flames may characterize the resulting fire more than smoldering smoke.

The innumerable combustion profiles possible with various fire loads and possible ignition sources preclude an easy set of rules to follow in selecting the type of alarm best suited for a particular application, (See paragraph 2.5.1.1 and Table A-4-6.1.1 in NFPA 72E-1990 for additional information).

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Situations Where Other Types of Alarms May be Used
In certain circumstances where smoke alarms are unsuitable, special-purpose alarms, such as flame detectors, heat detectors, and other detection devices may be suitable.

The application of these special types of alarms should be based on an engineering survey and used in accordance with the manufacturer’s installation instructions provided.

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Capabilities and Limitations of Smoke Alarms
American Sensors smoke alarms are designed to provide early warning of fire and smoke at reasonable cost. Early warning can mean the difference between a safe escape and no escape at all. While smoke alarms can provide invaluable protection for you and your family, they do have limitations.

Smoke alarms cannot work without power. Battery operated alarms will not work without proper batteries, with dead batteries or if batteries are not properly installed. AC powered alarms will not work if their AC power supply is cut off by an electrical fire, an open fuse, a circuit breaker or any other reason.

If you are concerned about the reliability of either battery or your AC power supply for any of the above reasons, you should install in your home both AC and battery powered smoke alarms for added security. American Sensors also offers the SA379 model which is AC powered with battery back-up.

Smoke alarms are incapable of sounding the alarm until smoke reaches the sensing chamber. Anything preventing smoke from reaching the alarm may delay or prevent an alarm. A smoke alarm cannot detect fire in the walls, chimney or roof unless and until a significant amount of smoke reaches the alarm. A closed door may prevent smoke from reaching an alarm on the other side of the door. A smoke alarm may not sense a fire on another floor of a home. For example, a basement smoke alarm may not detect a fire which started on the first or second floor.

Smoke alarms may not be heard. The loudness of the horn in your alarm meets current standards. However, the sound may be blocked by distance, closed doors, or ambient noise such as traffic or a stereo. Smoke alarms may not be heard by persons who are hard of hearing. For these reasons, a smoke alarm should be installed in every room or at least on every level of your home. American Sensors recommends that hardwire AC Powered smoke alarms be interconnected, so that one alarm will trigger all other alarms to sound their alarms.

Smoke alarms are not fool-proof. Smoke alarms may not always sense every kind of fire. They cannot be expected to sense fires caused by carelessness or by safety hazards. They may not give early warning of fast growing fires caused by smoking in bed, violent explosions, escaping gas, improper storage of flammable materials, overloaded electrical circuits, natural causes such as lightning, children playing with matches, or arson.

Smoke alarms are not substitutes for property, disability, life or other insurance of any kind. Home owners and renters should continue to insure their lives and property. Consult your insurance agent.

Smoke alarms have limited lives. One or more of the many components could fail at any time. Therefore, test your smoke alarm weekly. Clean and take care of it as described in this manual. Repair or replace the smoke alarm when it fails to test properly. Your smoke alarm should be replaced if it is ten years old.

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• In every room of your home (except the bathroom): Research indicates that substantial increases in warning time can be obtained with each properly installed, additional alarm.

• In bedrooms: In anticipation of fires originating within these rooms, caused by faulty wiring, lamps, appliances, smoking or other hazards.

• In hallways: At a distance no greater than 4 meters (13 feet) from the farthest wall and no greater than 8 meters (26 feet) from the next alarm.

• In the center of a room or hallway: As it is impossible to predict the source of a fire. If it is necessary to place the alarm on a wall, always locate the top of the smoke alarm 10-15 cm (4-6 inches) from the ceiling.

• As needed: To compensate for closed doors and other obstacles that may interfere with the path of smoke to an alarm. They may also prevent occupants on one side of a closed door from hearing an alarm on the other side of the door.

NFPA Recommendations

For your information, the National Fire Protection Association's Standard 72 reads as follows:

2-2.1.1.1 Smoke alarms shall be installed outside of each separate sleeping area in the immediate vicinity of the bedrooms and on each additional story of the family living unit, including basements and excluding crawl spaces and unfinished attics. In new construction a smoke alarm also shall be installed in each sleeping room.
A-2.5.2.1 Smoke Detection - Are More Smoke Alarms Desirable? The required number of smoke alarms might not provide reliable early warning protection for those areas separated by a door from the areas protected by the required smoke alarms. For this reason, it is recommended that the householder consider the use of additional smoke alarms for those areas for increased protection. The additional areas include the basement, bedrooms, dining room, furnace room, utility room, and hallways not protected by the required smoke alarms. The installation of smoke alarms in kitchens, attics (finished or unfinished), or garages is not normally recommended, as these locations occasionally experience conditions that can result in improper operation.

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• In turbulent air areas of your home such as fans, doors, windows, etc. The rapid air movement may prevent combustion particles from entering the alarm.

• In dead air spaces such as at the peak of an "A" frame ceiling. "Dead air" at the top may prevent smoke from reaching the alarm in time to provide early warning. In rooms with simple sloped, peaked or gabled ceilings, install smoke alarms on the ceiling 90 cm (3 feet) from the highest point of the ceiling.

• Note: For complex ceiling structures, consult a safety expert for the number of alarms required and the best locations.

• In very hot or cold areas where the temperature exceeds 38C (100F) or falls below 5C (40F).

• Less than 15 cm (6 inches) from the wall when mounted on the ceiling.

• Nuisance alarms could result when smoke alarms are located where interference may occur with the sensing chamber. To avoid nuisance alarms, DO NOT place smoke alarms:

• In high humidity areas such as bathrooms and attics. Place smoke alarms at least 3 meters (10 feet) away from bathrooms.

• In insect-infested areas.

• In poorly ventilated kitchens or garages.

• In very dusty and dirty areas.

• Near fluorescent lights. Place smoke alarms at least 1.5 meters (5 feet) from fluorescent lights.

Do not connect this smoke alarm to any other alarm or auxiliary device. Connecting the alarm to any other device may be detrimental to its proper operation.

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What To Do When Alarm Sounds
Don't waste time collecting possessions after a fire starts.

Arouse all occupants and leave the building. Your most valuable  possession is your life.

Doors can mean escape or death. Never open doors without first checking for heat. Test them with your hands, if they feel warm, fire may be walled up behind them - leave closed and find another escape route.

Call the fire department from OUTSIDE the building.


If you live in a high rise building, never use the elevator to escape fire.  If the fire blocks your exit, close your apartment door and cover all cracks where smoke could enter.  Telephone the fire department, even if fire fighters are already at the scene, and tell them where you are.  Shout for help and signal your location by waving a bright cloth, towel or sheet out of a window.

NEVER re-enter a burning building.

Keep your family in a pre-arranged meeting place after your escape.

Devise an escape route using a floor plan of your home.

If your clothes catch on fire, “Stop, Drop and Roll” to put out the flames.  Do not run--running will only increase the flames.

Your local fire department may be able to offer you additional ideas for safety and escape plans in the home.

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Planning Your Escape
Families should get together and draw an escape route using a floor plan of their home.  They should show two ways out of every room.  The first way should be out a door and the second way could be through a window.  If it is a second or third story window, they might consider purchasing a safety ladder.  (If so, everyone should know how to use the safety ladder.  Children should practice using one with an adult supervising).  They should choose a meeting place for all family members outside the home and mark it on the plan.  A good meeting place would be a driveway, tree or a neighbor’s home.   

Families should practice the escape plan to make sure everyone understands the planned routes.  Involve every member of the family.  Start with everyone in their beds with the doors closed.  Have one person sound the smoke alarm.  Have each person touch his or her door.  (Tip:  sleep with bedroom doors closed.  A closed door will help slow the spread of fire, smoke and heat).  Practice two escape routes--one for a cool door and one for a hot door.  Meet outdoors at the assigned meeting place.  Designate one person to call the fire department.  Make sure everyone knows the fire department or local emergency telephone number.

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Safety Tips
Properly installed and maintained smoke alarms are an essential part of a good home fire safety program. Your fire safety program should also include a review of fire hazards and the elimination of dangerous conditions whenever possible. Consider the following tips:

• Use smoking materials properly. Never smoke in bed.

• Keep matches and cigarette lighters away from children.

• Store flammable materials in proper containers. Never use them near an open flame or sparks.

• Keep electrical appliances in good condition. Do not overload electrical circuits.

• Keep stoves, fireplaces, chimneys, and barbecue grills grease free. Make sure they are properly installed and away from any combustible materials.

• Keep portable heaters and open flames such as candles away from combustible material.

• Do not allow rubbish to accumulate.

• Keep a supply of extra batteries on hand for your battery powered smoke alarms.

• Do not stand too close to the alarm when the unit is in alarm as the loud horn could damage your hearing.

WARNING! Never disconnect the battery or the AC power on any type of smoke alarm to silence a nuisance alarm. Clear the area of smoke by opening doors or windows or fanning the smoke away.

Most important, when fire strikes, a prepared and practiced escape plan can make the difference between life and death. Develop an escape plan and practice it with the entire family, including small children.

• Ensure all family members are familiarized with the alarm signal.

• Prepare an escape plan. Draw a Floor Plan of Your Home and determine two exits from each room. There should be a way to get out of each bedroom without opening the door.
                          

• Have Fire Drills Often. Practice your Escape and BE PREPARED.

• Decide on a meeting place at a safe distance from your home.

• In Case of fire

• Don't waste time collecting possessions after a fire starts.

• Arouse all occupants and leave the building. Your most valuable possession is your life.

• Doors can mean escape or death. Never open doors without first checking for heat. Test them with your hands, if they feel warm, fire may be walled up behind them - leave closed and find another escape route.

• Call the fire department from OUTSIDE the building.

• If trapped inside, stay close to the floor, cover mouth with cloth, conserve breath as you crawl to safety.

• Keep all doors and windows closed except for escape purposes.

• NEVER re-enter a burning building.

• Keep your family in a pre-arranged meeting place after your escape.

Your local fire department may be able to offer you additional ideas for safety and escape plans in the home.

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Maintenance and Troubleshooting
VACUUM EVERY SIX MONTHS
Your Smoke Alarm should be cleaned every six months to help keep it working efficiently. Open cover and gently vacuum interior of alarm. Keep vacuum nozzle from touching unit.

Do not paint the unit.

TEST WEEKLY BY PRESSING TEST BUTTON

PROBLEMS MAY BE INDICATED BY THE FOLLOWING:

• The alarm does not sound upon pressing the test button.

• The alarm does not sound with the smoke test.

• The operating light remains steadily on or off (i.e. does not flash once every 45 seconds, when the unit is not in alarm).

TRY THE FOLLOWING:

• Inspect for obvious damage.

• Gently vacuum as recommended above.

• Check that unit contains recommended battery type.

• Check that batteries are properly connected.

• Replace battery.

If these procedures do not correct the problem, do NOT attempt repairs. If the smoke alarm is within warranty period and terms, indicate the nature of the problem and return the unit with proof of purchase to the point of purchase, distributor or manufacturer. See below for instructions. Units beyond warranty cannot be economically repaired.

FALSE ALARMS:
Abnormal air conditions may cause the highly sensitive smoke alarm to give a "false" alarm. If no fire is apparent, ventilate the room and/or blow fresh air into the unit until the alarm stops. Once cleared, the smoke alarm will automatically reset.

DO NOT DISCONNECT THE BATTERY.

Dust can lead to excess sensitivity. Vacuum as recommended above.

U.S. Consumer Product Safety Commission Warns That Smoke Alarms in About 16 Million Homes Do Not Work

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