Photoelectric vs Ionization – What Is the Best Type of Smoke Detector

Smoke Alarms—Ionisation or Photoelectric?

The purpose of a smoke alarm is to sense the presence of smoke in the home and to audibly alert the occupants, to give them time to escape to a safe place.

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Photoelectric smoke alarms are much faster at detecting smoldering fires than ionisation smoke alarms. Research has shown that photoelectric smoke alarms typically respond to smoky fires within a few minutes while the level of smoke is still low and the air breathable, allowing more time to escape safely. Ionisation detectors should be replaced with photoelectric detectors.

How do you know if you have an ionization alarm?

These will often go off when you burn the toast but are slow to react to slow smoldering fires that occur while you are asleep.

Check the alarm for a radiation symbol, it may be displayed on the outside or the inside of the unit.

A comprehensive study on residential smoke alarm technology was recently completed by the National Institute of Standards and Technology, along with Underwriters Laboratories, the US Fire Administration, the US Consumer Product Safety Commission, the US Centers for Disease Control and Prevention, and other sponsors. This work evaluated current and emerging smoke alarm technology responses to common residential fire scenarios and nuisance alarm sources (the link to published work on the NIST website is

Still not convinced? Check out this test:

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