SMOKE ALARMS

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SMOKE ALARMS and HEAT DETECTORS

Smoke alarms aren't new. The technology has been around since the 1960s. The single-station, battery-powered smoke alarm, similar to the one we know today, became available to consumers in the 1970s. NFPA estimates that 93% of U.S. homes have at least one smoke alarm. They save so many lives that most states have laws requiring them in residential dwellings.

Although 13 of every 14 homes have at least one smoke alarm, almost half of home fires and three-fifths of fire deaths occur in the share of homes with no alarms. Thousands of people still die each year in home fires where smoke alarms aren't present.

In addition, there are now more homes with smoke alarms that don't work than homes without alarms at all. These poorly maintained units create a false sense of security among occupants. Approximately one-third of homes with smoke alarms that experience fires have smoke alarms that aren't working, and hundreds of people die each year in these fires.

Tragically, the grave importance of installing and maintaining smoke alarms has not yet been fully realized. Most people who die in home fires are not in the room where the fire starts; working smoke alarms alert people to fire and give them time to escape in a situation where minutes can mean the difference between life and death.

Having a smoke alarm cuts your chance of dying nearly in half if you have a home fire. By properly placing, regularly testing and maintaining your alarms, you can ensure that they are in fact working and will alert you if a fire breaks out. Make sure you buy only those alarms that bear the mark of an independent testing laboratory. Some alarms operate using an "ionization" sensor while others use a "photoelectric" sensor. An ionization alarm uses an extremely small quantity of radioactive material to make the air in the alarm chamber conduct electricity. Smoke from a fire interferes with the electrical current and triggers the alarm. A photoelectric alarm uses a tiny light source shining on a light sensitive sensor. The alarm is triggered when smoke from a fire interferes with the light. All tested and labeled smoke alarms offer adequate protection if they are properly installed and maintained.

A recent NFPA report on smoke alarms found that there is a substantial number of households that do not have the devices on every level of the home, as needed. The majority of fire deaths occur at night when people are asleep. NFPA's National Fire Alarm Code (NFPA 72) says homes must have smoke alarms on every level of the home -- including the basement -- and outside each sleeping area. New homes are required to have a smoke alarm in each sleeping area as well.

To slow the spread of smoke and fumes if a fire develops, NFPA suggests that you sleep with your bedroom doors closed. If you sleep with your bedroom doors closed, install a smoke alarm inside each bedroom. Alarms should also be installed in other areas of your home where people sleep. In new homes, the National Fire Alarm Code requires hard-wired alarms to be interconnected, so that if one alarm is activated, all alarms will sound the alarm signal. On floors without bedrooms, smoke alarms should be installed in or near living areas, such as family rooms and living rooms.

Alarms that are hard-wired into the home electrical system should be installed by a qualified electrician. If your alarm plugs into a wall socket, make sure it has a restraining device to keep its plug from being pulled out. Never connect an alarm to a circuit that could be turned off at a wall switch. Most alarms are battery-powered and can be installed with a screwdriver and drill and by following the manufacturer's instructions.

Since smoke and deadly gases rise, alarms should be placed on the ceiling at least 4 inches from the nearest wall, or high on a wall, 4-12 inches from the ceiling. This 4-inch minimum is important to keep alarms out of possible "dead air" spaces, because hot air is turbulent and may bounce so much it misses spots near a surface. Installing alarms near a window, door or fireplace is not recommended because drafts could detour smoke away from the unit. In rooms where the ceiling has an extremely high point, such as in vaulted ceilings, mount the alarm at or near the ceiling's highest point. In all cases, smoke detectors should be installed in accordance with the manufacturer's instructions.

It is imperative that you keep your smoke alarms fit and in good shape. The two most common reasons for inoperable smoke alarms are:

Disabling them to prevent nuisance alarms.

Neglecting to replace units that are past their 10-year service lives.

Maintain your smoke alarms by:

Testing

Whether your alarms are hard-wired or battery-operated, NFPA recommends testing them once a month to make sure they are operating. A working smoke alarm greatly reduces your chances of dying in a home fire. Testing is the only way to ensure they are working to protect you. Test each alarm by pushing the test button and listening for the alarm. If you can't reach, stand under the alarm and push the test button with a broom handle.

Replacing Batteries

If your smoke alarms are battery operated, replace their batteries according to the manufacturer's instructions. NFPA recommends doing this at least once a year or when the alarm chirps, alerting you that the battery power is low. Replace the batteries immediately if you move into a new home. Make sure no one disables your smoke alarms by borrowing batteries for other uses. Everyone you live with should understand how critical it is to have working smoke alarms.

Cleaning

Just as you clean your home, your smoke alarms need to be cleaned. Make sure you follow the manufacturer's instructions about cleaning. Cobwebs and dust usually can be removed with a vacuum cleaner attachment. If you are going to be doing work nearby that could send dust in the air, cover the alarm with a shield. Also, shield the alarm if you are painting around it, and never paint on it. Remove the shield promptly after work is completed.

Nuisance alarms are a serious problem. If a smoke alarm repeatedly sounds when there is no fire, the owner is likely to disable it. But then it cannot respond in case of a real fire. How serious is this problem? When surveyors from the Consumer Product Safety Commission (CPSC) visited homes, they found that one third of the smoke alarms were inoperable. The biggest reason for disabling them was nuisance alarms.

Here are the reasons given for disabling smoke alarms, ranked from the most frequent:

Cooking.

Alarm sounds continuously when powered.

Alarm sounds intermittently.

Steam or humidity.

Cigarette smoke.

Loose battery connection.

Most nuisance alarms from cooking involve smoke alarms with ionization-type sensors. (Note: A discussion of the two principles of smoke detector sensors is provided later in the Frequently Asked Question section.) That is because this type of sensor is sensitive to very small smoke particles, even particles that are invisible to the naked eye. Cooking routinely gives off small, "invisible" smoke particles.

There are two basic solutions. Either move the unit or replace it with another type of smoke alarm that is less sensitive to cooking. Moving the smoke alarm farther away from the cooking area can allow the cooking vapors to thin out before reaching the alarm unit. But this does not always work, especially if the air current through the kitchen goes toward the smoke alarm. An example is an apartment where the air current flows from the kitchen down the hall to the bathroom and passes out through the bathroom vent. In this case, placing the smoke alarm farther down the hall from the kitchen may still leave it in the path of cooking vapors.

The second solution, replacement, gives you three options. The first option is to buy a new ionization-type smoke alarm that has a "Hush" button. Pressing the hush button silences the unit for about 15 minutes, hopefully enough time for the cooking vapors to dissipate. The second option is to buy a photoelectric smoke alarm. Photoelectric units are less sensitive to small smoke particles so they are more resistant to cooking vapors. Although this makes them slower than ionization-type units to respond to flaming fires (they give off more of the smaller smoke particles), the time difference is fairly short.

The third replacement option is a unit that contains both the ionization and photoelectric sensors. This might sound strange at first because we have said that ionization sensors are more sensitive to cooking. But, when they are combined with a photoelectric sensor, the manufacturer can make the ionization sensor more resistant to the small smoke particles that come from cooking vapors. Thus the owner can have the advantage of both sensors and reduce nuisance alarms from cooking.

If a smoke alarm sounds continuously, it is either too dirty, too old or faulty. The sensor in a smoke alarm can become more sensitive as it gets older. As time goes by, it will need fewer smoke particles to make it respond and it may start to sound continuously. All residential type smoke alarms should be replaced when they are ten years old. And although it is rare, even new smoke alarms can fail. If a fairly new smoke alarm sounds continuously, then it should be returned for a new one.

What about intermittent alarms when there is no fire? Like the problem with a continuous alarm, the reasons could be an older unit that is getting more sensitive, or a dirty or faulty unit. In addition, people often mistake the low-battery signal for a nuisance alarm. When the battery is getting low, smoke alarms are designed to "chirp" every minute or so while the battery still has enough power to warn you that it is about to stop working.

The "chirp" is distinctive because it is a single, very short sound that occurs every minute or so. If your smoke alarm does this intermittently, first replace the battery to see if that solves the problem. If not, then the unit needs replacement due to old age or needs cleaning. To clean the unit, place the end of a vacuum cleaner hose next to it and sweep around all of the openings. This should dislodge any dust that has accumulated on the screening. If the dirt is visible and cannot be dislodged, the only practical answer is to replace it.

Steam or humid air can condense on the sensor and circuit board, and enough condensation will cause it to operate. Moving the unit farther away from sources of steam and humidity, e. g. bathroom doorways, can solve the problem. However, if the smoke alarm did fine in its location but is now reacting to steam or humidity, the problem can be age-related due to increased sensitivity. Older smoke alarms that become more sensitive are more likely to respond to steam and humidity than new units. The nuisance alarms may be a sign that the unit is over 10 years old and needs to be replaced.

Normally, a smoke alarm will not respond to cigarette smoke unless it is very concentrated, e. g, a large group of smokers in the same room. Standing close to the unit and blowing into it can cause it to respond, but this is not a normal situation, either. Older smoke alarms that have become more sensitive may begin to respond to lower smoke concentrations. Again, if the unit was fine in a normal smoking environment but is now beginning to respond, it is probably a sign of old age.

There is no practical way to repair a loose battery connection. This is more likely to happen as the unit gets older and has had several batteries replaced. It too, is a sign that it is time to replace the unit.

Fire protection in the home must start with smoke alarms. There are many other kinds of alarms which may be designed to detect such factors as high temperatures, rapid changes in temperature, and certain gases produced in fires. However, these alarms are not as effective as smoke alarms in giving the first warning when a fire breaks out. NFPA does not require heat alarms in homes, however, they may be used for optional extra protection in areas like kitchens, attics, and garages, where smoke alarms are susceptible to nuisance alarms.

Tests performed on the speed of warning given by smoke alarms and heat alarms for many types of typical home fires showed smoke alarms consistently give first warning -- often by enough of a margin to make a major difference in your chances of escaping alive. Smoke and deadly gas spread farther and faster than heat.

Contrary to popular belief, the smell of smoke may not wake a sleeping person. Instead, the poisonous gases and smoke produced by a fire can numb the senses and put one into a deeper sleep.

Heat detectors

Heat detectors are now referred to as heat alarms. Smoke alarms consistently respond much faster than heat alarms. NFPA 72 does not require heat alarms in either new or existing homes. It does, however, contain recommendations for additional protection in Appendix A, and refers to heat alarms there. The primary recommendations in the appendix are for more smoke alarms, but heat alarms are also addressed.

The reference in the appendix recommends heat alarms for areas in the home where smoke alarms are not recommended. The examples include garages, attics, unheated crawl spaces and kitchens. The air in the spaces like garages can become too hot or cold for smoke alarms to operate properly. Smoke alarms are not recommended for kitchens if the cooking causes nuisance alarms. On the other hand, if the smoke alarm does not cause nuisance alarms, then its location is fine.

For all other spaces like living rooms, dens, dining rooms and bedrooms, the NFPA standard recommends smoke alarms. It cautions you against depending primarily on heat alarms. The Consumer Product Safety Commission takes a similar position.

** This Article provided courtesy of the Wake County Fire Marshals Office.

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