Ionization smoke alarms monitor 'ions,' or electrically charged particles in the air. Air molecules in a sample chamber of ionization smoke alarms, are 'ionized' by a radioactive source. This allows a small electrical current flow. Smoke particles entering the sensing chamber change the electrical balance of the air. The greater the amount of smoke, the higher the electrical imbalance. When combustion particles enter the smoke alarm, they obstruct the flow of the current. An alarm is pre-programmed to sound when the current gets too low.
Ionization smoke alarms respond first to fast flaming fires. A flaming fire devours combustibles extremely fast, spreads rapidly and generates considerable heat with little smoke.
Ionization alarms are best suited for rooms, which contain highly combustible material. These types of material include:
1. Cooking fat/grease
2. Flammable liquids
5. Cleaning solutions
Smoke alarms with ionization technology are the most popular types sold in the United States.