There are many options to choose from when selecting a smoke alarm, however the most important component of any alarm is the sensor. There are two different types of smoke sensor:
Ionization Smoke Alarm
This sensor type is best at detecting fast flaming fires. The ionization sensor creates a charge in the air between two plates, causing a measurable current. When smoke enters the chamber, it changes the current which is detected and activates the alarm. Ionization smoke detectors are ideal for bedrooms and basements and are generally the less expensive option.
Photoelectric Smoke Alarm
This sensor type is best at detecting slow smoldering fires. The photoelectric sensor uses a light source within a sensing chamber. When a fire causes smoke to enter the chamber, it reflects light onto the sensor which is detected and activates the alarm. Photoelectric smoke detectors are ideal for hallways near kitchens and bathrooms, as the photoelectric technology greatly reduces false alarms.
Combination Ionization / Photoelectric Smoke Alarm
These alarms combine both Ionization and Photoelectric sensor types to detect both fast flaming fires and smoldering fires which cause a large amount of smoke. A combination Ionization / Photoelectric alarm gives you the benefits of both sensor technologies.