Smoke alarms can take more than nine minutes to go off and others fail completely, putting lives at risk, experts warn.
Some alarms do not offer proper protection despite meeting official safety standards, they said.
The consumer group Which? found huge variations in the length of time it takes alarms to sound. And one device failed two out of four standard smoke tests.
The need for smoke alarms was highlighted by the Grenfell Tower blaze, in which more than 80 died.
It is believed some residents had alarms in their own homes, but there was no system for the entire block.
Smoke alarms can take more than nine minutes to go off and others fail completely, putting lives at risk, experts warn
The Which? study suggests even those who do have alarms may not be fully protected.
Its experts tested 15 alarms – all of which had passed tests by the British Standards Institution (BSI) – to see how quickly they sounded during fires caused by wood, cotton, plastic or solvents.
Which? said: ‘We experienced a repeated pattern of safe-seeming products having wildly varying response times.’
In tests with smouldering wood, a First Alert device and an Ei Electronics one took more than nine and a half minutes to go off. The best alarm tested, Nest Protect, was more than four minutes quicker.
One device, Devolo’s Home Control Smoke Detector, failed to go off in two of four tests. It was adequate on smoke from wood and cotton, but failed for ‘fast flaming’ fires caused by plastics or solvents.
Which? called on the company to remove the product from sale and reported it to Trading Standards. Despite the variations, all response times met the BSI standard.
Which? said: ‘The safety consequences of a slow-to-sound fire alarm could be significant. In a house fire, every moment may count when getting you and your family to safety.’
The need for smoke alarms was highlighted by the Grenfell Tower blaze, in which more than 80 died. It is believed some residents had alarms in their own homes, but there was no system for the entire block
Which? called on the company to remove the product from sale and reported it to Trading Standards. Despite the variations, all response times met the BSI standard
Alex Neill, of the consumer group, added: ‘People will be surprised to see such a big variation in response times from alarms currently classed as safe. We want to see stricter testing criteria.’
BSI said it was confident about its standard, but is working on improvements. Devolo said it aims to follow the highest safety standards and that its alarms passed tests at two certified labs.
Dan Daly, of the London Fire Brigade, said homes ‘need multiple alarms or you won’t be properly covered’, including in rooms where you leave electricals running or charge mobiles or laptops, adding: ‘As a minimum you should have alarms on every floor, in the hallways and the rooms you use most. It is vital people test their alarms once a month.’