The consumer watchdog tested five smoke alarms in accordance with the British Standard, including fires involving wood, cotton, plastics and solvents. Two different samples of each model were tested in each scenario.
One alarm – sometimes listed as the SS-168, but often unbranded – failed to detect smoke in seven out of eight tests. The first sample failed to detect smoke in any of the four tests. The second failed to sound in three fire tests.
A Which? investigation in June led to dozens of carbon monoxide alarms being removed from sale on Amazon and eBay after they also failed safety tests.
The latest investigation follows the testing of five smoke alarms last year, which led to the Devolo Home Control Smoke Detector being made a Don’t Buy, after one of its samples tested failed to sound for plastics and solvents fires.
Several models available on the high street struggled in the testing. The Honeywell XS100 failed to sound in two of the eight tests, despite carrying the Kitemark safety label. The first sample did not sound at all during the wood fire test and the second sounded too late in the plastics test.
The results of this year’s testing also highlighted serious concerns about the time some alarms took to detect smoke. Two samples of the FireAngel SO-601 detected smoke and sounded in all four testing scenarios, but both were deemed slow. In the wood test, the SO-601 was more than five minutes slower than the Best Buy Nest Protect, and with the cotton fire it was two-and-a-half minutes slower.
Alex Neill, Which? managing director of home products and services, said: “It’s shocking that some of the products we’ve tested are either far too slow or don’t work at all in some circumstances. Anyone who has one of these alarms should replace it.
“We think the safety standards need to be strengthened and the government must take action to prevent products that falsely claim to meet safety standards from entering people’s homes.”
Honeywell said the alarm is certified to the highest European Standards, has third party accreditation and is effective at detecting smoke quickly. EBay said it has removed all 100 contentious listings from its site.