On a typical morning last September, Liz McConnell, a mother of four, was preparing to start her workday at her home in Dover. However, her routine was disrupted when a fire alarm sounded, prompting her to investigate the source of the noise.

McConnell's search led her to the tumble dryer, which was emitting smoke and heat. Upon closer inspection, she discovered that a part of the machine was on fire, highlighting the potential dangers of household appliances.

McConnell promptly contacted the fire brigade, which advised her to evacuate the premises immediately. The Kent Fire & Rescue Service responded to the incident, battling the blaze for several hours and ultimately leaving the McConnell family home partially destroyed.

McConnell acknowledges the crucial role that smoke alarms played in alerting her to the fire, stating that they are "essential" for ensuring safety in the home.

Despite their importance, smoke alarms have undergone relatively little technological change in recent years, raising questions about their ability to keep pace with modern life and the evolving nature of fire hazards.

For instance, detecting fires caused by e-bike batteries can be particularly challenging due to their potential to ignite suddenly. Researchers are exploring new methods for sensing smoke and fire, with the goal of developing more effective and efficient detection systems.

According to Suzanna Amberski, head of customer and building safety at Kent Fire & Rescue Service, the presence of a working smoke alarm can significantly reduce the risk of fatalities in the event of a fire. Her organization has found that approximately 6,500 smoke alarms in Kent properties had expired between 2022 and 2024.

A survey conducted by Direct Line in December found that nearly four million UK adults may be living in homes without any smoke alarms, while an estimated 16% of households in the US lack functioning smoke alarms.

There are two primary types of smoke alarm technology, explains Raman Chagger, principal consultant at the Building Research Establishment. Ionisation-based systems utilize a small amount of radioactive material to charge particles in the air, which flow between two plates and trigger the alarm when interrupted by smoke.

Optical-based smoke alarms, on the other hand, employ light to detect smoke particles. These systems are more effective at identifying large smoke particles produced by slow-burning fires, which scatter light and trigger a photoelectric sensor.

Heat sensors, commonly installed in kitchens to minimize false alarms caused by cooking, typically sound when temperatures exceed 50C.

The standards for evaluating smoke alarms were developed in the 1980s, but despite changes in building materials since then, smoke alarms remain a reliable means of detecting fires, according to Chagger.

Chagger has personal experience with the importance of smoke alarms, having had a fire alarm sound in his own home due to a tumble dryer fire. He stresses the importance of installing smoke alarms in the same room as potential fire hazards, such as tumble dryers.

The increasing popularity of e-bikes poses a new challenge for smoke alarm technology, as lithium-ion batteries can produce toxic and flammable gases when they fail. Stephen Welch, senior lecturer at the University of Edinburgh's Fire Research Centre, notes that these gases can accumulate and ignite, resulting in explosions.

Experiments conducted by Chagger have demonstrated the rapid development of lithium-ion battery fires, which can progress from a minor issue to a major explosion in a short period.

Some smoke alarms, such as aspirating devices, are designed to be highly sensitive and can detect small quantities of smoke in a room. These systems are often used in commercial settings, including server rooms and data centers.

Niki Johnson, fire systems technical adviser for the UK Fire Association, notes that aspirating systems are commonly used in stately homes and other high-value properties, but can be expensive to install, with costs ranging from £3,000 to £4,000 for a single corridor.

The rise of smart technology has led to the development of wi-fi connected smoke alarms that can send notifications to users' phones in the event of a fire, providing an additional layer of safety and convenience.

Nick Rutter, co-founder and chief executive of FireAngel, explains that his company's connected alarms use a proprietary radio system to link devices and send push notifications to users' phones via their home internet router.

Rutter emphasizes the importance of reducing nuisance alarms, which can lead to people disabling or removing their smoke alarms, thereby increasing the risk of fire-related injuries or fatalities.

FireAngel has calibrated its alarms to minimize false positives and reduce the likelihood of nuisance alarms, which can be a significant problem in many households.

Kidde, another smoke alarm manufacturer, offers a subscription-based service that provides access to a fire monitoring system linked to the Ring doorbell app. For a monthly fee of $5, users can receive alerts and have trained agents request emergency assistance in the event of a fire.

Isis Wu, president of global residential fire & safety at Kidde, notes that the system can send alerts to users and ask them to confirm whether they need assistance before contacting the fire department.

Kidde's smart alarm also features a low-battery alert that is designed to minimize disruptions, such as alerting users during the night when they are likely to be asleep.

Future smoke alarm technology may incorporate artificial intelligence and machine learning to detect fires in video feeds. Researchers at New York University have developed a system that can identify fire and smoke in footage from any camera, including CCTV, doorbell cameras, and phone cameras.

The system uses machine learning to analyze the size, shape, and growth of fires, allowing it to distinguish between actual fires and images of fires on screens.

The researchers have also attached the detection system to drones, which can be used to help firefighters locate and respond to fires in high-rise buildings or other complex environments.

The team is currently working to commercialize the technology, with the goal of making it widely available for use in a variety of applications.