You might be surprised to know that there are more than one type of smoke detector. Not only are there two primary types of smoke detectors but each one is better at sensing different types of fires. This brief article will help you understand the differences as well as which ones are best given your specific needs. The two most commonly recognized smoke detection technologies are ionization smoke detection and photoelectric smoke detection.
Ionization smoke detectors are generally more responsive to flaming fires. These type of smoke detectors 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. Download this chart on ionization smoke alarms (PDF, 943KB)
Photoelectric smoke detectors are generally more responsive to fires that begin with a long period of smoldering (called “smoldering fires”). These type of smoke detectors aim a light source in to a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light on to the light sensor, triggering the alarm. Download this chart on photoelectric smoke alarms (PDF, 782 KB)
Which one is right for your home? That is a question you need to answer for yourself based on your requirements. Some safety groups suggest using both types of smoke detectors and others suggest only using only one type.
The International Association of Fire Fighters only recommend photoelectric alarms.
In most fatal fires there are two STAGES of fire. The fire smolders then eventually it bursts into flames. The ONLY smoke alarm that reliably operates in the early, smoldering STAGE is the photoelectric. When a fire is lit without a smoldering stage, a photoelectric alarm will give adequate warning. However, ionization alarms are proven by scientific testing and legal precedents to be unable to reliably detect fire in the early, smoldering stage.
Sources: NFPA National Fire Protection Association, IAFF International Association of Fire Fighters