There are two major 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. To maximize your fire protection, you should install both types (or a combination of the two) to make sure you are completely covered.