Every year in the United States, more than 3,500 people die in home fires and another 18,000 are injured. Additionally, house fires cost almost $8 billion in property damage annually. Many victims do not die of burns but rather smoke inhalation, because fires often occur at night when victims are asleep.

Smoke detectors are the best way to prevent these catastrophic results. It is recommended that every home not only have smoke detectors but also at least one working fire extinguisher.

The risk of dying from an unprotected home is twice that of a protected home. Approximately 95% of U.S. homes have at least one smoke detector, yet 20 percent of fire fatalities occur in homes with broken or disabled detectors.

Fire starts from a chemical reaction between oxygen in the atmosphere and some sort of fuel (most commonly wood or gasoline). For combustion to occur, the fuel has to reach its ignition temperature. When the heated material is burning, it gives off volatile gases, or smoke.

Smoke has compounds of hydrogen, carbon, and oxygen along with byproducts of char (except for gasoline fires), ash, and heat. The chemical reactions in a fire generate new heat, which is what sustains the fire. The heat of the flame keeps the fuel at the ignition temperature, so the fire continues to burn as long as there is fuel and oxygen around it. The flame heats any surrounding fuel, which in turn spreads the fire.

Fires from different fuels behave differently; therefore, a fire from a fast-burning fuel that produces a lot of heat will inflict a different sort of damage than a slow-burning, low-heat fire.

When properly installed and maintained, smoke detectors can save your life and the lives of your loved ones at a relatively minuscule cost. Before the concentration of smoke reaches a dangerous level, or before the fire becomes too intense, an alarm sounds to warn you.

It is recommended that every home have at least one smoke detector per floor. You can buy one for as little as $10. (For the various choices and options, see the article on reliable smoke detector manufacturers.)

Smoke Detector Types

There are many brands of smoke detector on the market, but they all fall under two basic types—ionization chamber detectors and photoelectric detectors. Both types have two basic parts: a sensor to sense the smoke and a very loud electronic horn to alert people. They come either battery-powered or hardwired.

Ionization detectors use a radioactive source that produces electrically charged molecules (ions). This sets up an electrical current within the detector chamber. When smoke enters the chamber, it attaches to the ions and reduces the flow of electrical current, which sets off the alarm. Ionization detectors are better at detecting the smaller amounts of smoke produced by fast, flaming fires.

Photoelectric detectors use an optical detector sensor (a photo beam) and go off when smoke from a smoldering fire is dense enough to deflect that beam of light.

Because homeowners cannot predict the type of fire that might start, a combination smoke detector—called a dual-sensor smoke alarm—can be a wise choice.

Battery-powered detectors are easier to install and will continue to work during a power failure. The batteries last approximately one year. When they need replacing, the detector will chirp every minute or so to indicate that the batteries are expiring.

Hardwired detectors operate on a household electrical current and operate as long as the house has power. Plug-in units need to be located near an electrical outlet where they will not be unplugged or turned off by a wall switch.

Hardwired smoke detectors should not be plugged in with the use of an extension cord and should always utilize the hold-in clips provided to prevent accidental plug removal from the outlet. Hardwired detectors typically have a battery as a power-supply backup in case of a power failure.

Smoke Detector Features

In addition to the chirping noise that indicates the batteries need changing—a standard feature—some smoke detectors also offer:

• A remote-control mute button that can be linked to a television remote control to silence nuisance alarms.

• Safety lights to provide illumination during an alarm.

• Silence buttons that will quiet the alarm for a few minutes at a time. Detectors with this feature are commonly placed in kitchens.

• Transmission of a signal to a central monitoring station as part of a security alert system.

• Intercommunication of hardwired smoke detectors that guarantees if one alarm in the house goes off, they all go off. Even if the fire is detected in the basement, people upstairs will hear an alarm.

Combination Detectors

Combination detectors are gaining in popularity because they combine smoke and carbon monoxide detection. They are available as CO and ionization alarms and CO and photoelectric alarms.

By purchasing these combo alarms, you would have fewer alarms to place in your home (except that many CO alarms mount in the typical wall outlet placed low on the wall while the optimum smoke alarm placement is on or near the ceiling).

Interconnecting CO detectors warn you of problems in remote areas of the house—especially important in multi-level homes. They can be linked through hard wires or wirelessly and set off all the alarms if any one goes off.