“They are essential” describes how smoke detectors are changing.

The school race was over and the laundry was in the tumble dryer. Liz McConnell, a mother of four and stepmother, was scheduled to sit for work at her Dover home last September. However, the sound of a fire alarm interrupted his morning.

She walked towards it and eventually found smoke coming from the tumble dryer. Upon touching the machine, he realised that it was hot, and upon looking closer, he saw that parts of it were on fire.

“At that time I called the fire brigade,” she recalls. They advised him to leave the property immediately. McConnell says the fire spread “very quickly.” The McConnell family home suffered partial destruction as Kent Fire and Rescue Service battled the blaze for hours.

“Wouldn’t I have heard? “I would have just been there [the smoke alarm],” McConnell says. “They are essential, absolutely essential.”

Smoke alarms have been around for many decades. The technology has barely changed recently, but is modern life slowly outpacing the capabilities of these life-saving devices?

For example, detecting an e-bike battery fire is especially difficult because these can appear suddenly. Some researchers are working on new ways to sense smoke and fire, perhaps more quickly than before. But keep in mind: any certified, working smoke alarm is better than nothing.

“People are almost 10 times more likely to die in a fire if there is no working smoke alarm in the property,” says Suzanna Embersky, head of customer and building safety at Kent Fire and Rescue Service. His organisation alone found almost 6,500 expired smoke alarms on Kent properties between 2022 and 2024.

At the national level, A survey by insurer Direct Line Suggestions published in December suggests that almost four million UK adults could be living in a home without a smoke alarm. In America, it is estimated that 16% of homes do not have a working smoke alarm.

There are two main types of smoke alarm technology.

says Raman Chagger, principal consultant at the Building Research Establishment (BRE). Ionization-based systems: use a small amount of radioactive material to charge or ionise air particles flowing between two small plates. If smoke disrupts the flow of charged particles, an alarm is triggered.

Optical-based smoke alarms use light instead. They are slightly better at detecting large smoke particles produced by slow, smouldering fires. When such particles enter a chamber of the instrument, they scatter light from a small light source, which is then picked up by a photoelectric sensor.

Heat sensors are often installed in kitchens to avoid false alarms if you’re burning toast, which usually sounds when the temperature climbs above about 50°C.

The tests used in the standards for evaluating smoke alarms were developed in the 1980s. However, despite changes in construction materials since then, Smoke alarms remain reliable; Chagger says, “They still respond to all the major fires we get today.”

And Chagger has personal experience of tumble dryer fires. A few years ago, a fire alarm went off in his own home – in the room where his tumble dryer was running. Upon closer inspection, he realised that a thin layer of smoke hovered below the ceiling above the machine. Chagger was able to deal with the fire safely and says he recommends installing a smoke alarm in the same room as the tumble dryer.

But e-bikes with lithium-ion batteries are a new challenge. “When a battery fails, it won’t necessarily burn; it will often produce some off-gases,” says Stephen Welch, senior lecturer at the University of Edinburgh’s Fire Research Centre. “Those gases are toxic and flammable. If they accumulate, there can be a risk of explosion.”

Chagger has recorded the following in experiments: How do lithium-ion batteries catch fire? “It’s absolutely incredible,” he says. “Then, nothing happens; gases are released, and there are multiple explosions.”

Some smoke alarms are designed to be extra sensitive. For example, aspirating devices continuously draw air to detect small amounts of smoke in a room. These are often used in business settings, including server rooms filled with expensive computer technology.

“Many stately homes will have that system,” says Nicky Johnson, owner of the UK Fire Association, a trade body, and owner of fire detection firm Derventio Fire & Security. “You could be looking at £3-4,000 just to build one corridor.” He explains that such installations require substantial pipework.

One of the biggest developments in the fire alarm area in recent years has been the rise of smart technology – Wi-Fi-connected alarms that reach out to you by phone if, for example, they sense smoke while you’re outside.

“Our internet-connected devices use a proprietary radio system that links the alarms together,” says Nick Rutter, co-founder and chief executive of FireAngel. Connected alarms can send push notifications to users’ phones through their home internet router.

He suggests that the smoke alarm industry has a responsibility to reduce nuisance alarms, which sometimes cause people to deactivate or uninstall their devices – a huge safety risk.

“If we’re producing technology that our customers can’t live with, that’s our failure,” he explains, adding that FireAngel alarms are calibrated to avoid being overly sensitive to reduce false alarms.

Another smoke alarm company, Kidde, has developed a subscription-based service that charges users US$5 (£3.71) per month for access to a fire monitoring service linked to the Ring Doorbell app. “Trained agents can request emergency assistance and alert the customer’s emergency contacts in the event of an alarm,” Kidde explains on its website.

“In the event of a fire, it will send you an alert and ask you to confirm before calling the fire department,” says Isis Wu, its president of global residential fire and safety.

The company also has a smart alarm that avoids alerting users about low battery during the night when they are sleeping, as this often results in people turning off their alarm and forgetting about it.

Future smoke alarms may use completely unique technology. Researchers have developed an AI-based system that uses machine learning to detect fires in video feeds. The device can detect fire and smoke in footage from any camera—including CCTV, doorbell cameras, and phone cameras, according to Prabodh Panindre of New York University.

“We monitor the size, shape, and growth of the fire,” he adds, explaining that this helps avoid false alarms caused by photographs of fires or fires on TV screens that are visible in the footage.

Panindre and his colleagues have also linked the detection system to drones, which could help firefighters detect fires in a high-rise building: “These drones can actually go around the building and capture the location of the fire.”

He says the team is now working to commercialise the technology.