'Silent danger' button most cars have you should never use for longer than 20 mins

A medic has issued an urgent warning to motorists of the 'silent dangers' from a common car dashboard button. Posting on Instagram, Dr Christabel Akinola highlighted the potential consequences of leaving the air recirculation button on for more than 20 minutes.

She warns it could cause drowsiness, headaches and poor concentration, increasing the risk of a road accident, reports Yorkshire Live. In a recent Instagram post, she said: "Is this your first time hearing about this silent danger? Please let others know."

Sharing the possible risks of keeping the button on for too long, she cautioned: "Check the dashboard of any car you ride in, and never leave the button on for more than 20 minutes at a stretch."

She added: "There's a button inside your car right now that, once pressed, can cost you your life within 2-3 hours, and the painful thing is, most people have no idea what it does. It's silent and deadly."

Dr Akinola explains what happens when you activate this button: "It shuts off outside air and recirculates the air already inside your car."

She went on: "It cools the car faster with air-con, keeps out dust and other pollutants. But this should only be turned on for a maximum of 15-20 minutes. If kept on for too long, carbon dioxide (CO2) from your breath builds up, leading to drowsiness, headaches, poor concentration and fatigue.

"This is one of the reasons drivers fall asleep and don't know why or how, leading to accidents. Please, before you ride in any car and during the trip, make sure you check the dashboard to ensure it's turned off, especially if you have kids."

The medical expert then offered some advice on what to do instead, sharing the following steps:

• "Use recirculation only for short bursts (10-20 minutes), like in traffic or dusty areas."
• "For long trips, switch to fresh air mode regularly."
• "If you're driving and suddenly feel drowsy, open a window, especially if passengers start feeling sleepy as well. Pull over. It might not be fatigue. It might be the air."

In the comments, one person wrote: "This just saved my life. Because I was feeling all these signs, then I realised mine was on upon seeing this. I never took notice. Thank you so much for sharing."

Another said: "Wow, this is so educative! Sometimes, when I'm in the car, I feel so drowsy and feel like vomiting. Now I know the cause."

Another recounted their experience, writing: "I used to get drowsiness when I turned on this function too long. Max I can do with it was 5min. It's dangerous." Someone else claimed: "This is why I have been dizzy so bad lately, that button is always on in my car." And another person added: "I actually learnt this the hard way."

One person asked: "Doesn't the button auto shut off after a few minutes? Or is that just Ford?" Someone replied: "Not all cars have that feature apparently."

Although the air recirculation button is a standard feature, it is not present in every car. Many modern vehicles come with sensors that automatically control air circulation according to the conditions inside the cabin, removing the necessity for a manual button.

Studies have revealed that heightened levels of CO2 in vehicles can lead to fatigue, drowsiness, and a decrease in cognitive function, potentially increasing the risk of accidents. High concentrations of CO2 can also cause headaches, lack of focus, and other discomforts.

The more passengers in a vehicle, the higher the production of CO2. Lengthy trips and traffic jams can worsen the buildup of CO2, as occupants are exposed to the same air for extended periods.

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Research has discovered that for every 500 ppm increase in CO2, a driver's reaction time decreases by 2.4%. At 1400 ppm, basic decision-making skills are reduced by 25%, and complex strategic thinking is cut by approximately 50%, according to experts from the University of Colorado Boulder.

While low levels of CO2 are generally safe, concentrations exceeding 5,000 ppm can cause issues such as headaches and shortness of breath. Levels above 40,000 ppm are deemed immediately hazardous to life and health.

Although elevated levels of carbon dioxide (CO2) in a car can cause drowsiness and impact a driver's alertness, they are not instantly life-threatening like carbon monoxide (CO) poisoning. CO2 poisoning primarily results in suffocation due to a lack of oxygen, but the concentrations required to be fatal in a car are highly unlikely to occur.

More commonly, increased CO2 levels in a car can lead to drowsiness and reduced alertness, which may result in accidents.