Ionization smoke alarms are very common in the US. It's likely that the current smoke alarms in your house fall in to this category. These type of alarms rely on a tiny amount of a radioactive substance called Americium 241 to help detect smoke particles in the air (see the infographic below for details).
Ionization smoke alarms are best at detecting a flaming type of fire. They do not work as well as detecting a smoldering fire in the house. An ionization smoke alarm does provide a warning for fires it can detect it may not be the best choice to cover all potential types of house fires. A better option is a dual function smoke alarm - one that has both ionization and photoelectric sensors. Look for a post next week that explores photoelectric type alarms.
Brian Jovag, owner of Jovag Home Inspection.