“I understand there are two kinds of smoke alarms. What is the difference between them and which type should I buy?”
The types of smoke alarm technologies available today are the photoelectric and the ionization types. Photoelectric alarms react faster to fires that begin with a long period of smoldering, such as would occur from a fire starting in a modern sofa or bed. Ionization smoke alarms react faster to fast starting flaming fires, such as a grease fire on a stove.
The best evidence has always indicated that either type of smoke alarm will provide sufficient time for escape for most people for most fires of either the smoldering or flaming type. However, because you cannot predict the type of fire you will have in your home or when it will occur, the United States Fire Administration recommends installing both ionization AND photoelectric smoke alarms, OR dual sensor alarms that contain ionization and photoelectric sensors in them. The dual sensor alarms will provide the best response to any fire and therefore the most time for escape.
Keep in mind that state law now requires a carbon monoxide detector/alarm in all residences that have a gas burning appliance (such as a furnace, hot water heater, or stove) or an attached garage. In addition to the dual sensor smoke alarms discussed above, combination smoke and carbon monoxide alarms are also available today.
Answered by Kris Krengel
Division Chief/Fire Marshal