Sian Welby's 'uncontrollable tiredness' caused by common car feature

Sian Welby thought something might have been wrong when she came down with 'uncontrollable tiredness' whilst driving. But she never expected her car to be the culprit.

Offering advice to "anyone who drives", Sian shared her discovery with listeners to the Capital Breakfast radio show she hosts alongside Jordan North and Chris Stark. The 38-year-old star said it was only a chance scroll on TikTok that helped her pinpoint the problem that was instantly solved by disabling the feature most modern cars have.

In a clip to her Instagram feed with its 274,000 followers, Sian wrote: "We had lorry drivers and taxi drivers texting in saying the button had been on in their cab the whole time and they never noticed it! So dangerous and most of us don’t know about it!"

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She told her co-hosts that she "thought she had a bit of an issue" with car journeys that lasted over 30 minutes, especially if they involved a motorway. She said: "I didn't know if it was sort of the rhythmic motion of the car on motorways or the mundane view you've got of constant tarmac, but it would 'send me to sleep' - and I'm talking uncontrollable tiredness.

"I started thinking 'what is wrong with me?'. Even if I had a good night's sleep, I'd be pinning my eyes open on these long journeys."

The radio host, who also occasionally presents ITV's This Morning, mentioned how it's often impossible to drive with windows down on a motorway without having a "horrendous" noise in your ear. The most obvious solution for a cool and fresh breeze is the air conditioner (if your car has it).

Sian added that a random scroll on TikTok brought her to a video which claimed watching it "could save your life". She initially thought it was going to be "a load of nonsense" but it ended up giving her the solution to all her problems on the road.

She continued: "When you've got air conditioning in your car, you've got two buttons, and there's one that shows a car with arrows—the recirculation button. A lot of us were told that it would save energy if you put that on because it recycles the air inside your car and it cools down quicker - that's true.

"However, apparently, it's not designed to be left on and it can cause drowsiness. So I thought, right, this could be a load of nonsense but if I get into my car and that button is on, it might be why I'm getting tired.

"I go in my car and, sure enough, that button is on. I turned it off and I did a three-hour motorway journey the other day - didn't feel tired once."

It's not just mind over matter - there's a scientific reason why people should limit how often they use the recirculation button. Studies show that recirculated air inside a car contains decreased oxygen levels and increased carbon dioxide levels.

The air conditioning recirculation button should ideally be used in short bursts, typically for no more than 20 minutes. Some vehicles may have a built-in timer that automatically switches off recirculation after a set time to allow fresh air into the cabin.