All About Smoke & Carbon Monoxide Detectors

According to the National Fire Protection Association (NFPA), approximately two-thirds of U.S. household fire deaths result from homes with no smoke alarms or smoke alarms in which the batteries are dead, disconnected or missing.  Another 400

deaths occur annually from carbon monoxide poisoning.

Whether it is a household setting or a business, the selection and maintenance of an early warning system is crucial to save

lives and minimize property loss.

A & K Services of Iowa is here to help you sort through the confusion of protecting your family and home from fire and

deadly carbon monoxide.  Proper selection and installation is key to providing the best protection possible in each individual situation.  Contact us today and let us help you correctly protect what is most important to you.       

Types of Smoke Alarms and Detectors

There are two broad types of fire alarm systems - heat detectors and smoke alarms.  Knowing the differences between the various types of fire alarms available is key to matching the appropriate product to the application.

  • Heat Detectors

Heat detectors are the oldest type of automatic fire detection.  Heat detectors feature a detecting element inside the unit that activates when it reaches a predetermined fixed temperature or when a specific increase in temperature has occurred.  Heat detectors are best suited for:

  1.  applications where detection speed is not a prime consideration.​

  2.  where ambient conditions would not allow the use of a smoke detector.

  3.  fire detection in small, confined spaces where rapidly burning, high heat fires are anticipated.

Heat detectors have a lower false alarm rate​, but they are also slower than smoke detectors in detecting fires.  Studies have shown that heat detectors are not as effective as smoke detectors in detecting fires in residential homes.

  • Ionization, Photoelectric and Combination Ionization/Photoelectric Smoke Alarms

Smoke alarms will detect most fires more rapidly than heat detectors.  There are currently three types of smoke alarms on the market:  ionization, photoelectric, and combination ionization/photoelectric.

An ionization smoke alarm contains a small amount of radioactive material.  The radiation passes through an ionization chamber which is an air-filled space between two electrodes and permits a small, constant current between the electrodes.  Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm.  This type of alarm responds best to fast raging fires.

Photoelectric smoke alarms operate using a light source, a light beam collimating system and a photoelectric sensor.  When smoke enters the optical chamber and crosses the path of the light beam, some light is scattered by the smoke particles, directing it at the sensor and thus activating the alarm.  This type of alarm responds best to slow smoldering fires.

Combination ionization and photoelectric smoke alarms feature both types of these technologies in a single unit.  Ionization smoke alarms respond faster to high energy fires, whereas photoelectric detectors respond better to low energy smoldering fires.  The NFPA recommends using both types of smoke alarms in the home for the best protection.

Types of Carbon Monoxide Detectors

Carbon monoxide is a colorless, tasteless and odorless compound produced by the incomplete combustion of carbon-containing materials, such as gasoline, propane, natural gas, oil or wood.  This also may occur due to a malfunctioning fuel-burning device or other fuel-burning source.  Common sources of carbon monoxide include open flames such as fireplaces, furnaces, space heaters, water heaters, blocked chimneys or running a vehicle engine in a closed space such as a garage.

  • Carbon Monoxide Detectors

A carbon monoxide detector or CO detector is a device that detects the presence of carbon monoxide gas in order to prevent carbon monoxide poisoning.  CO detectors are designed to measure CO levels over time and sound an alarm before dangerous levels of CO accumulate in an environment, giving people adequate warning to safely ventilate the area or evacuate.

There are three basic types of CO detectors:  metal oxide, biomimetic and electrochemical.  Devices are also available as combination smoke and CO detectors.

Metal oxide CO detectors are the original type of CO sensing unit.  These work when the heated tin oxide reacts with CO to determine the levels of the toxic gas.  When the level of CO reaches a predetermined level that is considered to be unsafe, the alarm will sound.

Biomimetic CO detectors have gel coated discs that darken when the presence of CO is detected.  When the color of the discs change beyond a set point, the alarm will sound.

Electrochemical CO detectors operate through a chemical reaction that takes place when the chemical is exposed to CO.  This chemical reaction creates an electrical current which sets off the alarm.  This type of detection is the most sensitive and accurate of the three types.  Most present-day detectors are also this type.

Combination CO and smoke alarms offer protection from both hazards in a single unit.  These alarms use electrochemical technology as described above and may use ionization, photoelectric or a combination of both for smoke detection.  Depending on the model, these units may be battery powered, hard-wired or plug-in type.

Power Sources

Alarms​ may vary in how they are powered.  Battery powered alarms are very popular due to their low cost, however care must be taken to replace the battery on a regular basis.

Hard-wired alarms use the structure's wiring.  The interconnected feature of hard-wired alarms allows all alarms to be linked together.  This allows for all alarms to sound when one unit is activated.  This is especially important in homes with multiple levels or in apartment structures.  All hard-wired units are required to have a battery back-up feature so that the alarms will sound in the event of a power failure.

It should be noted that many jurisdictions require hard-wired alarms in residential installations with a battery backup.  This is the law in the State of Iowa in cases of new construction or in remodel settings where access exists for the installation of hard-wired units.