what is the difference in Ionization smoke sensor and photosence

Thank you for your question, Dave. Ionization smoke alarms are generally more responsive to flaming fires. How they work: Ionization-type 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. Photoelectric smoke alarms are generally more responsive to fires that begin with a long period of smoldering (called “smoldering fires”). How they work: Photoelectric-type 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; triggering the alarm.