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For Six Weeks I Thought I Was Going Out Of My Mind. Turns Out My Own Flat Was Slowly Poisoning Me.

My doctors couldn't explain it. What a Gas Safe engineer found on my hallway wall left me speechless.

My doctors couldn't explain it. What a Gas Safe engineer found on my hallway wall left me speechless.

— Sandra Hale

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It started with the small things.

A headache every morning that I put down to bad sleep. By the afternoon my head felt full of cotton wool. I'd read the same email three times and still not take any of it in.

Then it got harder to hide. I forgot my own PIN at the till. I called a colleague by the wrong name in a meeting, twice. One evening I drove home and couldn't, for a few seconds, remember which turning was mine, on a road I'd lived on for six years.

I'm in my thirties. This wasn't supposed to be happening to me.

I became convinced something was seriously wrong with me.

It got worse through the winter. I'd lose my temper over nothing, then not remember why. I missed a deadline I'd never normally have missed. I started waking at 3am with my heart racing and my head pounding, then crashing asleep at my desk by the middle of the afternoon.

I did what you do at 2am when you're frightened. I googled. Brain tumour. Early-onset dementia. Some breakdown I hadn't seen coming. I half-convinced myself I was seriously, permanently ill, and I was too scared to say it out loud to anyone.

So I went to my GP. Then £400 private. Nothing.

Bloods came back normal. Blood pressure fine. "It's most likely stress and poor sleep," I was told, kindly. I went back two weeks later, no better. Same answer.

In the end I paid £400 to go private, certain they'd find the thing the NHS had missed. They ran more tests and told me the same thing in nicer words. I walked out starting to believe it really was all in my head. Which, when your head is the thing that feels broken, is its own special kind of fear.

What finally cracked it wasn't a doctor.

It was my sister, an A&E nurse, on a video call one Sunday. She stopped me mid-sentence. "You look grey," she said. "You're slurring a little. You've told me three times you can't think straight, you're not sleeping, you've got headaches every morning." Then, quietly: "Before you spiral about your brain, when did you last have your gas checked?"

I almost laughed. The boiler was fine. We'd had it serviced. I couldn't actually remember when.

A Gas Safe engineer came the next morning.

He clipped a meter to his belt the moment he stepped inside. Within a minute he stopped talking, looked at the reading, and very calmly, which somehow made it worse, told me to open every window and step outside with him.

The boiler flue had a hairline crack. Carbon monoxide had been leaking into a flat I'd spent all winter sealing shut: new double glazing, draught excluders, the lot. Airtight. Filling up a little more each night.

Then he told me what CO does to you long before it kills you. Headaches. Confusion. Wrecked sleep. Memory gaps. Mood swings you can't explain. Every symptom that had terrified me for six weeks, he had seen before.

The alarm wasn't broken. It was built to stay silent.

I pointed at the alarm on my hallway ceiling. Green light on. Two years up there. It had never made a sound.

Standard alarm

50 PPM
silent below this, but you're already ill at 30 to 45 ppm

Sentinel alarm

10 PPM
alarms early and shows the live number from zero

"It's not broken. It's doing exactly what it's certified to do, which, at the levels that were making you ill, is nothing."

Then I started checking the numbers for myself. They're worse than I expected:

~40 deaths a year from accidental CO poisoning in England & Wales, and roughly 4,000 A&E visits. Experts say many more go unrecognised, because it looks like stress or flu. (ONS / DHSC)
42% of UK homes have no working CO alarm at all. Nearly one in two. (Firechief Global)
NEW It isn't just old houses. Some of the worst cases are brand-new builds with badly fitted boilers, the homes people assume are safest.

But the statistic that stopped me cold wasn't about dying. It was about surviving. CO starves your brain of oxygen, and people who pull through low-level exposure can be left with lasting damage to memory, concentration and mood. In one UK case, a mother poisoned slowly by her boiler scored on a cognitive test comparable to someone in their 80s, and doctors compared it to a stroke. Her GP missed it for months.

It doesn't just kill you in your sleep. It can quietly take pieces of who you are, and because it feels like stress, most people never join the dots until the damage is done.

What the engineer fits in his own home.

Before he left, I asked him what I should actually buy. He didn't hesitate. Forget the £15 discs, he said. Get a detector with a digital screen that shows the live CO number from zero, a reading you can look at any time, and one that alarms at 10 ppm, not 50. Early. While you can still do something about it.

The one he fits in his own home, and the one I went with, is the Sentinel. A 4-in-1: it watches carbon monoxide, natural gas, propane and temperature, in real time, on the screen. It plugs straight into a socket. No ladder, no electrician, thirty seconds and it's on. And it's loud enough to wake the whole flat.

That night I threw the old one in the bin.

I plugged the Sentinel in by my bedroom door. First reading: 41 ppm. Seeing an actual number, not a light but a number, for the air I'd been sleeping in for weeks, did something to me I can't quite describe. I got the boiler fixed that week and watched the figure come down. 30. 18. 9. Then zero.

The headaches were gone within the week. The 3am wake-ups stopped. The fog lifted, and the words came back.

And I got off lightly.

For six weeks I thought I was losing my mind. I wasn't. My own flat was quietly poisoning me, and the alarm I trusted watched it happen and stayed silent, exactly as it was designed to.

I live alone. I keep thinking about the homes where someone doesn't. Kids asleep down the hall. A baby in a sealed nursery. An older parent in the next room. Children, infants and pets feel it first and worst, because they have smaller bodies and breathe faster. They can't tell you their head hurts. They just go quiet.

If you've been explaining away headaches, fog or broken sleep, or you've got a child or a pet that has gone flat, and there's anything that burns gas in a home you've sealed up for winter, please don't wait. Stop trusting a light. Look at the actual number.

This is the detector I use now.

I linked the same detector below.

https://trustsentinel.co.uk/pages/sentinel-offer-page

If you have one of those detectors with just a green light, you don't know what you're breathing.

You don't know if you're thinking clearly right now.

I thought I was being stalked for three weeks.

I was just being poisoned.

Don't wait until you can't tell what's real.

Check your detectors. If they don't show you real numbers, replace them with something that actually works.

(I linked the one I use down below)

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