Similarities:
Both Ion (Ionization) and Photo (Photoelectric) smoke alarms respond to combustion particles given off by developing fires. Both are designed to give adequate warning in case of fire, whether a fire starts slowly and smolders, or bursts into flames quickly and spreads rapidly.
Differences:
Ion and Photo sensing chambers use different methods to detect smoke. The differences between them are pretty technical, so let''s start with a simple analogy: Think of wrist watches. Some are digital, some have dials with hands. Both tell time, but they use different methods. Same idea with ion and photo smoke alarms.
Ionization: Ion smoke alarms react to changes in ionized particles. Ionization technology is generally more sensitive than photoelectric technology at detecting small particles, which tend to be produced in greater amounts by flaming fires, which consumer combustible materials rapidly and spread quickly. Sources of these fires may include paper burning in a wastebasket or a grease fire in the kitchen.
Photoelectric: Photoelectric smoke alarms react to how smoke affects light. Photoelectric technology is generally more sensitive than ionization technology at detecting large particles, which tend to be produced in greater amounts by smoldering fires, which may smolder hours before bursting into flame. Sources of these fires may include cigarettes burning on couches or bedding.
Is one better?
It''s impossible to say one sensor photo or ion is universally better at detecting all types of fires. Why? Because both sensors are designed to respond to combustion particles produced by smoldering or flaming fires, and because fires themselves are different. The combustion particles produced will vary depending on what starts the fire (matches, electrical fire, etc.) and what burns (paper, fabric, wood).
If a lit cigarette drops directly onto a couch, it is more likely to start a smoldering fire. If that same cigarette drops onto a newspaper on the couch, the resulting fire may be more characterized by flames than smoldering smoke.
Major testing under the National Bureau of Standards sponsorship confirmed either type of smoke alarm will give adequate warning in either type of fire.
The most important factor in protecting your family is having the recommended number of working smoke alarms installed in the proper locations.
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