When Tracey Condron began experiencing daily bouts of dizziness, fatigue, and nausea, she initially suspected a viral infection.

“I went from being energetic to feeling completely drained,” recounts Tracey, a 44-year-old mother with children ranging from 21 to 29 years old.

As these troubling symptoms persisted, she began to notice additional changes in her health.

“I frequently experienced brain fog, both at home and during my job,” says Tracey, who was working as a Special Educational Needs Assistant at a primary school at the time.

“I also started detecting overpowering floral and sweet scents that no one else could perceive,” she adds.

Her bewildered colleagues assured her that there was no discernible odor. “They thought I’d gone crazy,” admits Tracey, who resides in Rainham, Essex.

In fact, Tracey’s symptoms were due to her being slowly poisoned by carbon monoxide gas leaking from a faulty boiler in her bedroom – and were it not for the quick actions of her neighbours, she could easily have died as a result.

Because alone at home one January evening last year, four months after her symptoms began, things suddenly took a dramatic turn for the worse.

Tracey Condron was hit by daily episodes of dizziness, fatigue and nausea but thought it was from some sort of virus

Tracey’s symptoms were due to her being slowly poisoned by carbon monoxide gas leaking from a faulty boiler in her bedroom

Tracey remembers nothing beyond sitting on the sofa that evening – she can’t even recall getting into bed.

It’s only because her neighbours showed her footage from their video doorbell that she knows she staggered up their drive at around six the next morning.

‘I was so weak I looked like I was going to collapse,’ says Tracey. ‘I could barely knock. Luckily, they heard me and opened the door to find me looking like death.’ Her neighbours took her inside and called 999.

‘I started vomiting in their living room and was struggling to breathe,’ says Tracey. ‘Then apparently I went stiff as a board and started convulsing.’

By the time the ambulance arrived, Tracey was foaming at the mouth. She suffered two cardiac arrests (meaning her heart suddenly stopped beating) and had to be resuscitated twice.

In hospital, doctors were initially at a loss as to the cause of her sudden collapse. She was put into an induced coma to try to prevent the seizures she was having – fearing she might not make it, her family was called into the intensive care unit.

It was during discussions with her children, who mentioned that Tracey slept next to the boiler, that doctors at Queen’s Hospital, Romford, began to suspect carbon monoxide poisoning – and tests proved their hunch right.

Each year, over 100 people in the UK die as a result of carbon monoxide poisoning – while many others, like Tracey, survive and can be left with life-changing health problems.

The reason the gas, which is invisible and odourless, is so deadly is that it binds far more tightly to haemoglobin (a protein in red blood cells) than oxygen does, meaning it takes its place and so ‘reduces oxygen delivery to the brain and other organs,’ explains Dr Faye Begeti, a neurology specialist at Oxford University Hospitals.

‘The brain is especially vulnerable as it normally receives around a quarter of the heart’s blood flow to meet its high oxygen needs – without adequate oxygen the tell-tale symptoms of poisoning, such as fatigue, brain fog and nausea begin.’

(The phantom smells Tracey noticed might have been a sign of mini-seizures in the area of the brain that processes smells, but is not characteristic of carbon monoxide poisoning.)

‘Chronic low-level exposure can be particularly harmful, as symptoms such as headaches, fatigue, dizziness and cognitive fog can easily be mistaken for stress, viral illness or infection,’ adds Dr Begeti.

Neurology specialist Dr Faye Begeti explains that the gas is dangerous because carbon monoxide ‘reduces oxygen delivery to the brain and other organs’

As levels of the gas build up in the home, it can cause severe acute carbon monoxide poisoning and seizures due to profound hypoxia (lack of oxygen reaching the brain).

There can be long-term consequences, too.

Dr Begeti warns of delayed encephalopathy – a form of brain injury that can emerge days or weeks later – caused by ongoing inflammation in brain tissue and damage to the brain’s white matter (the wiring that allows different parts of the brain to communicate).

‘People may experience cognitive decline, personality change, gait problems, seizures or psychiatric symptoms long after the exposure has ended,’ she says.

Carbon monoxide (CO) is produced when there is insufficient oxygen when the fuel, typically gas, is burned by flame, or when fumes that should be safely vented outside leak back into the home due to faulty, blocked or poorly maintained heating systems.

According to the charity CO-Gas Safety, faulty heating and cooking appliances are most often implicated in leaks – but generators, boats and petrol-powered strimmers can all emit the gas.

But because the symptoms of poisoning often mimic viral illnesses ‘GPs may not suspect carbon monoxide’, says Stephanie Trotter, president and director of CO-Gas Safety.

‘Also blood tests – which measure carbon monoxide in the bloodstream – and, less commonly, breath tests, often give false negatives because the gas leaves the body very quickly.

‘Sadly, just because CO leaves the body quickly, it does not mean the person exposed will completely recover. Many go on to suffer lasting damage to the brain and nervous system,’ she adds.

‘If someone was exposed to a high level, or exposed for a long time, it can trigger ongoing damage in the body. This means a person might seem fine at first, then feel much worse hours, days, or even weeks later.’

As Dr Begeti explains, carbon monoxide has a half-life in the body of about four or five hours, ‘meaning roughly 75 per cent would be cleared in eight to ten hours’.

She adds: ‘In situations where someone is being exposed repeatedly, the gas may not be fully cleared before the next exposure begins, hence chronically building up.’

December is the deadliest month for carbon monoxide deaths because people tend to spend more time indoors and there’s an increased use of heating along with less ventilation due to windows being closed.

But there is a year-round risk with barbecues or camping stoves used in tents, caravans or enclosed spaces, posing a serious risk in the summer too, according to CO-Gas Safety.

Tracey now warns people on social media about the dangers of faulty boilers and the importance of having carbon monoxide alarms 

Research by University College London and Liverpool John Moores University in 2012 suggested that more than three million people in the UK are regularly exposed to carbon monoxide levels of 50 parts per million or higher which, while below the levels that cause immediate collapse, can still be dangerous over time.

‘Less than 2 per cent of carbon monoxide in the air can kill or maim in between one and three minutes – some survivors tell me their injuries are so bad they wish they’d died,’ says Stephanie Trotter.

After her symptoms began, Tracey had gone to her GP who gave her repeated blood tests to check whether she might be anaemic, for example, but each came back clear.

All the time the levels of carbon monoxide gas in her home were building.

By the time she got to hospital the lack of oxygen to her brain was so acute she was having one seizure after another and had a fractured spine and hip as a result.

She spent five days in a coma, during which she continued to have seizures – meaning doctors had to delay fitting a back brace to limit the movement of her spine and help it heal. Tracey was discharged two weeks later, a changed woman.

‘I could barely walk,’ she recalls. ‘I had to stay with my older daughter, who lives nearby, for a few weeks because I couldn’t manage on my own. Everything became difficult, lifting, dressing, shopping, even playing with my grandchildren [then aged four, two and seven months].’

Despite now taking takes anti-epileptic drugs, over a year on Tracey still suffers from regular seizures, some requiring urgent hospital treatment.

‘The last serious set of seizures was in September last year,’ she says.

‘I don’t recall it, but my daughter was on the phone and said I wasn’t making sense. I had multiple seizures and woke up a day later not knowing what had happened.’

The fractures in her spine and hip healed, but have left her with daily pain. And despite taking painkillers, her mobility is now so poor she has had to give up work and depends on others for everyday tasks such as making meals, cleaning the house and food shopping.

The damage to her heart – caused by the lack of oxygen – has now healed, but Tracey has panic attacks and has been diagnosed with post-traumatic stress disorder as a result of her ordeal. She is undergoing talking therapy.

‘Life is not easy and I hate not being able to play with my four grandchildren [now five, three, 17 months and five months] – but I’m so grateful to still be here and to have survived it,’ says Tracey.

Her gas supplier later confirmed her boiler was faulty; and a carbon monoxide detector installed by her landlord was also found to be not working.

‘It was wired in and showed a green light, so it looked like it was working,’ she says.

‘There were never any safety checks in the five years I’ve been here – if there had, I wouldn’t have suffered prolonged poisoning that nearly killed me.’

Tracey is so scared it will happen again that she now has carbon monoxide detectors in every room and warns people on social media about the dangers of faulty boilers and the importance of having alarms.

‘I sleep with the windows and doors open when my grandson stays over,’ she says.

‘He had actually stayed in my room on many weekends before I was hospitalised but thankfully, I’d always kept my bedroom door open when he was there. I dread to think what could have happened to him if I hadn’t.’

Tracey has an important message for others: ‘If I could tell people one thing, it’s to make sure you have a working carbon monoxide alarm that meets the official EN 50291 safety standard. It could save your life.’