Ionization smoke detectors are the cheapest type of smoke alarms there are. They are more sensitive than optical smoke detectors and therefore, more liable to issue a false alarm. They work by detecting minute smoke particles in the air.
How do ionization smoke detectors work?
Inside the smoke detector there is an ionization chamber which contains a tiny amount of radioactive material (commonly americium 241) which emits radiation (alpha rays). The radiation passes through an empty space between two plates that are connected together by wiring, and through which an electric current is run through.
The radioactive alpha rays ionize the air in the ionization chamber and complete a constant electrical current which the smoke detector reads as normal. But when a fire occurs, smoke particles fill the air and enter the smoke detector. These smoke particles disrupt the constant electrical current by attaching to the ionized air molecules. The smoke detector senses a drop in the electrical current within the ionization chamber and sounds the alarm.
For people concerned about radioactivity, please note that fluorescent lighting and TV and computer monitors all employ similar technology along such lines. The americium has a half life of 432 years which means it only emits a tiny amount of radiation to last that long. The alpha rays are also weak and do not penetrate beyond the walls of the smoke detector. So there is nothing to worry about.
What to look for in ionization smoke detectors
Ionization smoke detectors are highly sensitive and even cigarette smoke can trigger them off. The upside is that they will react fast to flaming fires that spread from easily combustible materials like paper or oil or grease. Such fires spread quickly so this faster reaction time may make all the difference between life and death.
When you’re looking for an ionization smoke detector, look out for these features:
- Bright strobe escape lights – During an actual fire, visibility is extremely poor so these lights are useful.
- Remote controllable mute button to silence the alarm in case of false alarms.
- Operates on lithium batteries. Lithium batteries can last 10-15 years without the need to change them.
- Secure battery compartments with auto lock to prevent tampering.
- Low battery warning ability.
For a comprehensive fire safety plan, combining optical smoke detectors with ionization smoke detectors in an interconnected network throughout the rooms and floors of a home works well to provide adequate protection.