Ionization vs. Photoelectric Units

Smoke Alarm Detectors | Ionization vs. Photoelectric Units

Odds are that you have a disc-shaped device on your kitchen wall or ceiling that allows you to rest easy. This is a smoke alarm. This device is specially built to alert you in time should a fire or fumes put your life in danger. The most commonly installed residential smoke alarms are the photoelectric and ionization units. Despite their similar look and purpose, the two distinctive smoke alarms are built to detect different smoke densities and fire types.

Differences between Ionization and Photoelectric Smoke Alarms


  1. Structural and Mechanical Differences

The ionization smoke alarm uses radioactive material, Americium-241, to ionize the air inside its internal sensing chamber. This causes the air in the chamber to conduct electricity between the two charged electrodes installed. Presence of smoke particles reduces the electric conductivity inside the chamber which sets off the alarm.

Photoelectric smoke alarms consist of a light sensitive sensor and a diode that emits light within their sensing chamber. When smoke particles enter the chamber, they scatter the light beam. This is immediately detected by the sensor and sets off the alarm.

  1. Types of Fires Detected

Photoelectric smoke alarms are quick to sense smoldering fires because they have a light emitting diode and an extremely sensitive light sensor. Smoldering fires emit a lot of smoke, are slow to develop, and can easily burn unnoticed for a long time. On the other hand, ionization smoke alarms sense flaming and fast fires quicker than photoelectric alarms.

  1. Nuisance Alarm Tripping

Ionization smoke alarms, located in the kitchen, are prone to nuisance alarm tripping. Their high smoke sensitivity is due to quick response of the unit’s ionization portion. Nuisance tripping from photoelectric alarms is rare.

  1. Radioactive Components

Ionization alarms have a radioactive element called Americium-241 while photoelectric alarms do not contain any radioactive materials.

  1. Popularity

Ionization Alarms are the most rampant smoke alarms used in Canadian households compared to photoelectric detectors.


Which is the Best Smoke Alarm to Install?

 The photoelectric smoke alarm is the best smoke detector to install in your home. This alarm has received numerous endorsements from top industry organizations including the International Association of Firefighters (IAFF). In order to remain safe, the IAFF and other fire safety organizations recommend that all Canadian homeowners should only install photoelectric smoke detectors.


The technology that is used in ionization smoke alarms causes a warning delay during smoldering fires. This is dangerous because smoldering fires emit a lot of smoke and poisonous carbon monoxide. In high airflow environments, ionization smoke detectors become weak, which increase their delays. In addition, ionization detectors are more susceptible to nuisance alarm tripping causing many owners to disable them. This leaves them unprotected.

Photoelectric smoke detectors are highly effective in detecting and warning against smoldering fires. They are also less susceptible to nuisance alarms. These alarm systems are affordable, easily available, and don’t go off when you burn toast.

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