Smoke detectors are probably the most common and popular of all home security devices. Every one who is even at least a little bit worried about home safety and security would have, at minimum, several smoke detectors installed in his or her home.

Types of smoke detectors

Even though there are many types and brands of smoke detectors on the market and in the hardware store, they all can be broadly divided in two categories. These two categories that distinguish the smoke detectors are: types of power and methods of detection.

Smoke detectors categorized based on their power supply

Under the power types, there are two types of smoke detectors—9-volt battery powered smoke detector and the multi-year lithium battery powered smoke detector.

The battery type smoke detectors

The advantages of the 9-volt battery power smoke detectors are that they are easy to install, move and of course, to maintain. However, one must check the battery of the smoke detector frequently, at least, once a month.

The multi-year lithium battery powered smoke detectors are relatively new smoke detectors. They come with a special battery that lasts for years. Unlike the 9-volt battery powered type smoke detectors, the lithium battery powered battery smoke detectors do not require their batteries be replaced frequently.

However, the battery of the lithium battery powered smoke detectors must also be tested frequently though just like the 9-volt type battery powered smoke detector.

The electric type smoke detectors

Electric smoke detectors on the other hand are hard-wired fire security devices. The advantages of electric smoke detectors are that since they do not use batteries, they are easier to maintain and they are never disabled because of lack of battery! In fact, electric smoke detectors with a battery back up are the safest smoke detectors.

There is however one big problem with electric smoke detectors. Some times, fires are caused by electrical short circuits causing an electric smoke detector to become useless. As a safeguard, it is therefore much better to have another smoke detector—a battery operated one as a backup!

Smoke detectors categorized based on their detection technology

Smoke detectors based on detection methods can also be divided in two categories. These two categories are ionization smoke detectors and photoelectric smoke detectors.

Ionization smoke detectors

Ionization smoke detectors work by forming an electrical path inside the smoke detector with a very small amount of radioactive material. When smoke enters the detector, the smoke molecules attach themselves to the ions and change the electrical current. This change in the current triggers the alarm.

Photoelectric smoke detectors

Photoelectric smoke detectors work by containing a light source (like a small light bulb) and a photocell that is activated by light. Usually, the light never reaches the photocell. However, when smoke fills the smoke detector, the smoke reflects the light towards the photocell. The photoelectric cell than triggers the alarm.

The best smoke detector

A natural question that might arise here is that which of these two is better. The answer is none. Both are unique in their ways of detecting fires of different types. While the ionization detector responds slightly quicker to flaming fires (like draperies), with smaller particles of combustion, the photoelectric detector responds quicker to smoldering fires (like a cigarette.)

Even though there detection method may differ, both these types of smoke detectors have to pass the same test to be certified as a Underwriter Laboratory's smoke detector, and both will warn you in almost all cases of fires.


Testing a smoke detector

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