There are two types of smoke alarms in general use: photoelectric and ionization. These smoke alarms sense the presence of smoke differently.
* Photoelectric Smoke Alarms are generally a smoke alarm with light-sensitive sensors that can detect smoldering fire very quickly. As smoke enters the chamber and crosses the path of the light beam, light is scattered by the smoke particles, aiming it toward the sensor, which in turn triggers the alarm. Smoldering fires begin slowly and burn without a flame for a long period of time. Many deaths from residential fires occur as a result of smoke inhalation rather than flames. Being able to detect smoke early can be a lifesaver, helping families to escape before the flames have even started and prior to potentially life-threatening smoke inhalation. These types of fires often occur when small flames from things like candles or cigarettes are left unattended.
* Ionization Smoke Alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm. Ionization smoke detectors respond faster to smoke from flaming fires than a photoelectric device does. Most flaming, fast-moving fires are a result flammable liquids, wood, or paper catching fire. These are items that produce flames right away and do not have as much smoke as a smoldering fire. Ionization devices more quickly detect low-smoke fires, setting off the alarm sooner.
The big factor between the two is that Ionization smoke alarms tend to respond faster to the smoke produced by flaming fires. While Photoelectric smoke alarms tend to respond faster to the smoke produced by smoldering fires. This leads to the question of which one should I use?
You can create the safest environment possible for your family by installing a mix of photoelectric and ionization smoke detectors. It’s too risky to go with one and not the other because there is no way to predict what type of fire threat your home may experience. Some smoke detectors utilize both ionization and photoelectric technologies. These types of smoke detectors are known as “dual” smoke detectors and are widely available at home improvement stores and online at a variety of price points and from several brands.