'Dangerous' button most cars have can make you feel tired if left on too long

'Dangerous' button most cars have can make you feel tired if left on too longThe convenient feature is 'not designed to be left on' for an entire tripCommentsLifestyleAndrew Nuttall U35 Lifestyle Writer14:48, 13 Apr 2026View 2 ImagesMost drivers are causing the problem themselves by ignoring one setting(Image: Getty)People are being made aware of the risks of leaving on a seemingly harmless setting in their cars for a long period of time. Forgetting to turn it off could lead to a sense of "uncontrollable tiredness" while driving, which can quickly become dangerous.‌Many cars come with an air recirculation button, which prevents outside air from entering and keeps the air inside the car circulating. It can be helpful to cool off quickly during the summer, save fuel, and keep out pollution and bad smells when you're stuck in traffic.‌However, as previously reported by the Daily Mirror, leaving the setting on for 20-30 minutes can be dangerous, as it reduces oxygen and increases carbon dioxide (CO2) levels, which can trigger drowsiness and reduce concentration. This was the case for Capital Breakfast and ITV's This Morning presenter Sian Welby, who learned about the risks first-hand.‌The 39-year-old said at the time that it was only during a chance scroll on TikTok that she realised the car button was part of a problem she had regularly been experiencing while driving. In an Instagram video, Sian said: "So dangerous and most of us don’t know about it!"The mum-of-one said she often found herself yawning and feeling tired on car journeys lasting over 30 minutes, especially if they involved a motorway. Describing it as a sensation of "uncontrollable tiredness", Sian soon realised it was a setting in most modern cars that was causing her problems.Content cannot be displayed without consent‌The radio host said: "When you've got air conditioning in your car, you've got two buttons, and there's on...