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Photoelectric Smoke Alarms Vs. Ionization Smoke Alarms
Are photoelectric smoke alarms more effective than ionization smoke alarms for “adjacent to kitchen” installations, to minimize nuisance alarms? Within the fire protection and prevention industry, it is recognized that neither sensor type, photoelectric nor ionization, is universally better at detecting all types of fires. Each sensor operates on a different principle and therefore may respond differently to various conditions. Ionization sensors may respond slightly faster to flaming fires, whereas photoelectric sensors may respond slightly faster to smouldering fires.
Notwithstanding these differences, to achieve ULC listing, both alarms must be tested to the same standard and meet the same requirements. Since you can’t predict the type of fire that will occur, installing both types of alarms in your home can enhance fire safety.
Nuisance alarms in homes from typical cooking activities are affected by the properties of the aerosol produced and its concentration, the location of an alarm relative to the source, and the airflow that transports smoke to an alarm. You need to know that there are a variety of options available.
It is not possible to say one sensor type is better that the other for reducing nuisance alarms in kitchen installations. Insta lling a photoelectric smoke alarm instead of an ionization smoke alarm may be one approach to reducing nuisance alarms. Other approaches might be to relocate the existing alarm a short distance away, replace the unit with a new one, or replace it with a unit that has a hush feature.
An ionization smoke alarm uses a small amount of radioactive material to ionize air in the sensing chamber. As a result, the air chamber becomes conductive permitting current to flow between two charged electrodes. When products of combustion enter the chamber, the conductivity of the chamber air decreases. When this reduction in conductivity is reduced to a predetermined level, the alarm is set off. Most smoke alarms in use are of this type.
A photoelectric type smoke alarm consists of a light emitting diode and a light sensitive sensor in the sensing chamber. The presence of suspended products of combustion in the chamber scatters the light beam. This scattered light is detected and sets off the alarm.
The two types operate on different principles and therefore may respond differently to various conditions. Ionization models are best suited for rooms that contain highly combustible materials that can create flaming fires. These types of materials include
flammable liquids, newspapers, and paint cleaning solutions. Photoelectric models are best suited for living rooms, bedrooms and kitchens. This is because these rooms often contain large pieces of furniture, such as sofas, chairs, mattresses, counter tops, etc. which will burn slowly and create more smouldering smoke than flames.
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 smouldering 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).
As stated by manufacturers of smoke alarms, the most important factor in protecting your family is having the recommended number of working smoke alarms installed in the proper locations. It is also recommended that since you can't be sure what types of fire might start in your home, you install both ionization and photoelectric smoke alarms in your home, or choose dual sensor smoke alarms which feature both sensors in one unit.
