This Sunday, phones across the UK will blare out another alarm as the Government tests its emergency alert system for the second time.
At 3pm on Sunday (September 7), the ‘Armageddon alarm’ will be sent to all 4G and 5G-enabled phones and tablets.
The alarm is designed to deliver ‘life-saving information’ in times of crisis, such as during a wildfire or storm.
However, a health expert has warned that the test might carry its own set of risks.
And those with underlying heart conditions may want to opt out of the alert ahead of time.
According to Dr Luana Main, an expert on acute stress responses from Deakin University, the emergency alarm could trigger heart attacks in some people.
Dr Main told The Daily Mail: ‘Sudden alarms like those used in emergency services can activate our flight-or-fight response, which is our body’s way of dealing with a sudden threat or stressor, even when there’s no actual danger.
‘In some rare cases, for individuals with underlying cardiac vulnerabilities, it is possible that it may trigger a cardiac event.’
On Sunday, the national emergency alert system will be tested for the second time. All phones in the country will produce a siren-like noise for ten seconds, even if they have been placed on silent
If you have ever watched a horror movie and felt your heart racing, then you already know how fear and shock can affect our bodies.
When we are surprised by a loud noise, such as the national emergency alarm, the shock can push our bodies into a highly excited state.
Dr Main says: ‘Our bodies react as if we are under threat.’
‘Our heart rate and blood pressure spike. Cortisol, our stress hormone, surges, contributing to anxiety, irritability, and long-term stress.’
In our evolutionary past, that surge of activity might have helped us survive a life-or-death situation, but in the modern day, it simply takes a toll on our bodies.
Dr Main’s research has shown that, when exposed to emergency alarms, participants’ heart rates spiked from an average of 74 to 111 beats per minute or higher.
Among firefighters, the sudden shock of the emergency alarms they receive is so severe that it presents a legitimate threat to their lives.
Studies in the US have found that almost half of all firefighter fatalities were caused by sudden cardiac arrest, 18 per cent of which occurred during the alarm.
A health expert has warned that the sudden shock of the alarm could trigger a heart attack in some rare cases. However, they stress that this is ‘highly unlikely’ (stock image)
During the upcoming national emergency alert system test, the alarm will not be nearly as loud or shocking as those used by the emergency services.
However, for vulnerable individuals, the sudden shock could still pose a risk.
Those risks are amplified significantly if the alarm wakes people from their sleep.
In some studies, researchers have found that blood pressure increases by up to 74 per cent after being woken by a loud alarm.
‘Sleep inertia may follow, especially if the alarm interrupts deep sleep, impairing cognition and mood for hours,’ says Dr Main.
‘Frequent nighttime alarms impact our sleep, which can compromise immune function and impair metabolism.’
Thankfully, the upcoming test will occur during daylight hours, so the effects on sleep should be minimal.
Dr Main maintains that the effects on healthy people are unlikely to be serious and that it is ‘highly unlikely’ that the alarm will cause cardiac arrest.
The loud sound of the emergency alert (pictured) may activate the body’s flight-or-fight system, triggering an increase in heart rate, a spike in blood pressure, and a flood of stress hormones
Likewise, the Government stresses that emergency alerts contain ‘life-saving information and should be kept switched on for your own safety’.
However, it admits victims of domestic abuse with a concealed phone ‘may find it appropriate to turn off alerts’.
So, if you are concerned and do wish to opt out of the alerts, the Government has laid out the steps for how to do it.
If on an iPhone, opt out by going to ‘settings’ and selecting the ‘notifications’ menu, then scroll to the bottom and turn off ‘severe alerts’ and ‘extreme alerts’.
If on an Android device, search your device settings for ’emergency alerts’ and then turn off ‘severe alerts’ and ‘extreme alerts’.
The government webpage says people should contact their device manufacturer for help if they are still getting alerts after opting out.
Also, depending on the manufacturer and software version of your phone, emergency alerts settings may be called different names.
These might include ‘wireless emergency alerts’ or ’emergency broadcasts’.
The emergency alert is used to warn if there is a danger to life nearby, in instances like extreme weather – although Sunday will only be a test
This Sunday will be the first time that the Emergency Alerts System has been tested in two years, following the system’s launch in 2023.
During the upcoming test, all 87 million mobile phones in the UK will vibrate and make a loud ‘siren sound’ for roughly 10 seconds, even if they are set to silent.
Phones will also display a message stating that the alarm is only a test and not a genuine threat to life.
When it was first tested, the emergency system sent a message to phones which read: ‘Severe Alert. This is a test of Emergency Alerts, a new UK government service that will warn you if there’s a life-threatening emergency nearby.
‘In a real emergency, follow the instructions in the alert to keep yourself and others safe.
‘Visit gov.uk/alerts for more information. This is a test. You do not need to take any action.’
Data about you and your device will not be collected or shared in any way during the test, regardless of whether you receive the alert or choose to opt out.
Since the message is sent automatically via the mobile networks, the government does not need your phone number to send the alert, nor will your number be stored for the test.
The alert system was used in Plymouth after an unexploded World War II bomb was uncovered and had to be removed
Since its introduction, the Emergency Alerts System has been used in real-life scenarios five times, primarily during major storms when there was a serious risk to life.
The largest ever use saw approximately 4.5 million people in Scotland and Northern Ireland receive an alert during Storm Éowyn in January 2025, after a red weather warning was issued.
The system has also been used in more localised incidents, such as when an unexploded World War II bomb was uncovered in Plymouth.
Similar systems are already used widely across a number of other countries, primarily for natural disaster preparation.
Japan has one of the world’s most sophisticated systems, which combines satellite and cell broadcast technology.
This system forms part of a wider scheme called J-ALERT that informs the public in case of earthquakes, tsunamis, volcanic activity, or missile threats.
South Korea frequently uses its national cell broadcast system to alert citizens about issues ranging from weather alerts and civil emergencies to local missing persons cases.
The US has a similar system to the UK that utilises ‘wireless emergency alerts’ to send messages that look like texts with a unique sound and vibration pattern.
