What kinds of fire alarms are there?

There are two types of fire alarms: ionization fire alarms and photoelectric fire alarms. Ionization fire alarms detect flaming, fast-moving fires – curtain fires, trash can fires, etc. Photoelectric fire alarms are best for smoky, smoldering fires, such as electrical fires that start out behind walls. There are also dual sensor fire alarms which, naturally, combine both types into one.