The two most common smoke detection technologies are ionization smoke detection and photoelectric smoke detection. Here’s the difference between the two:
Ionization smoke alarms are typically more responsive to flaming fires.
How do these detectors work? 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, and in turn, reduces the flow of current which activates the alarm.
Photoelectric smoke alarms are typically more responsive to fires that start with a long period of smoldering (referred to as “smoldering fires”).
How do these detectors work? Photoelectric smoke alarms aim a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light onto the light sensor, which triggers the alarm.
Therefore, both types of alarms serve an important purpose. Since you cannot predict the type of potentially fatal fire you may have in your home or when it will occur, it is recommended by virtually every recognized fire authority and safety expert – including the International Association of Fire Chiefs (IAFC), the National Fire Protection Association (NFPA), the U.S. Fire Administration (USFA), Consumer Product Safety Commission (CPSC) and Underwriters Laboratories (UL) that both (ionization and photoelectric) technologies be used in homes. In addition to individual ionization and photoelectric alarms, combination alarms that include both technologies in a single device are available.