Old smoke alarms do not function properly

The Finnish Safety and Chemicals Agency (Tukes) studied the sound volume and the smoke sensitivity of optical smoke alarms particularly. Based on the results, smoke alarms that have been in use for several years no longer work reliably, since their sound volume and sensitivity to smoke can deteriorate with time. The functionality of smoke alarms should be tested regularly, and they should be replaced with new ones every 5–10 years.

In early 2020, Tukes tested 94 smoke alarms that had been in use for 0–36 years. The project was a continuation to the similar project conducted in 2017–2018. The results of the earlier project also indicated that the functionality of smoke alarms deteriorates with time. The results of the earlier project required more in-depth research in the effects of time on the sound volume and smoke sensitivity of optical smoke alarms. 

Smoke alarm sound volume matters 

According to studies, adults wake up to alarms with a noise level of 75 dB(A) or higher. The noise levels measured in the new study were mainly over 85 dB(A). Some of the smoke alarms included in the study did not sound an alarm at all and for some, the deterioration in sound volume could be heard by ear alone. Of the tested smoke alarms, 14% fell into these two categories.

–    The deteriorated sound volume of a smoke alarm or a dysfunctional smoke alarm can be detected by simply pressing the test button on the device. That’s why testing your smoke alarm regularly is important, says Karoliina Meurman, senior officer at Tukes. 

The smoke sensitivity tests, and a test conducted with a polyurethane fire particularly showed that the reaction times of optical smoke alarms varied greatly when compared to ionisation smoke alarms.  The operation of an optical smoke alarm is based on measuring the light emitted by a source of light inside the smoke alarm. Ionisation smoke alarms measure the electrical conductivity inside the alarm device. Based on surveys conducted by Tukes, more than 70% of smoke alarms sold in Finland are optical.

–  Based on test results, ionisation type smoke alarms withstand time better and react more consistently to smoke than optical smoke alarms, says Meurman. 

Maintain your smoke alarm in working order and replace it sooner rather than later 

It is the duty of the occupant of a flat, i.e. the resident, to keep the smoke alarm in good working order. The battery and the sound volume of smoke alarms should be checked once per month by pressing the test button. To ensure the smoke alarm works properly, it should be replaced according to the manufacturer’s instruction, usually every 5–10 years. The alarm must carry an indication of the time of replacement recommended by the manufacturer, which is usually found at the bottom of the device.

In addition to Tukes, the partners of the new study on the ageing of smoke alarms included Finance Finland, the Central Association of Chimney Sweeps, Safety Investigation Authority, Emergency Services College, Ministry of the Interior, Finnish Association of Fire Officers and the Finnish National Rescue Association.

Link to the final report (in Finnish)

Further information:
Senior Officer Karoliina Meurman, tel. +358 (0)29 5052 651
email format: [email protected]