How Long Can You Sleep in a Closed Car?
4 Answers
It is generally not recommended to sleep in a sealed car for more than 3 hours. The duration of sleeping in a sealed car should not be too long, as the lack of fresh air circulation can lead to an increase in carbon dioxide concentration inside the vehicle, thereby increasing the risk of suffocation. Under normal circumstances, staying in a sealed car for more than 3 hours can cause discomfort symptoms such as abnormal heart rate and difficulty breathing. Therefore, it is advised not to sleep in a sealed car for more than 3 hours. Below are some hazards of sleeping in a car: 1. Limited Space: The confined space in a car can easily lead to muscle fatigue and neck stiffness. 2. Closed Doors: With the doors closed, there is a risk of oxygen deprivation and carbon monoxide poisoning. High temperatures can accelerate oxygen deprivation. 3. Vehicle Windows and Doors: With advancements in technology, modern vehicle windows and doors have excellent sealing properties, making the small interior space poorly ventilated. In cold and dry winters, resting with the heater on in a stationary car or in a poorly ventilated garage can lead to oxygen deprivation or even shock symptoms if the rest period is prolonged.
Last time I tried overnight camping in the car, personal experience proved this requires extra caution. The biggest risk of sleeping in a car is carbon monoxide buildup—even when turned off, interior materials slowly release harmful gases. Summer is more dangerous as the cabin becomes like a steamer, risking heatstroke within twenty minutes; winter poses carbon monoxide poisoning risks. A fully sealed conventional gasoline car can last at most one hour—it's best to leave windows slightly cracked. Newer electric vehicles with camping mode fare better by automatically ventilating, but still shouldn't exceed eight hours. For proper car rest, recommend using external air circulation plus sunroof gaps, and regularly checking physical condition.
Having repaired cars for twenty years, I've seen too many cases of oxygen deprivation inside vehicles. In an enclosed space, human breathing consumes oxygen while exhaled carbon dioxide levels rise rapidly. The air volume in an ordinary sedan is only sufficient for two adults to sleep for about three hours, even less with children. Some believe running the AC is enough, but idling a fuel-powered car with AC on produces lethal carbon monoxide - last year, an owner never woke up after sleeping this way in an underground parking lot. If you must rest in a car, always keep windows or sunroof open. Electric vehicles are slightly safer, but still require external circulation mode.
I paid special attention to this when taking road trips with my child. Children metabolize faster and face a much higher risk of oxygen deprivation in a sealed car compared to adults. I tested my SUV – with all windows closed, the carbon dioxide detector alarmed within just two hours. Now I teach my child: if trapped in the car, honk the horn continuously until help arrives. Parents parking to sleep must be extra vigilant – cracking a window is more effective than any AC, and it's best not to exceed two hours. Electric vehicles with air monitoring functions are relatively safer.
