How many hours can you sleep without opening the car window?

[VanJulia]

It is not safe to sleep in a car with the windows closed, as it can be fatal in severe cases. Here are the relevant details: 1. Hazards: If you sleep in the car for an extended period with the windows tightly shut and the air conditioning on recirculation mode, the confined space of the car will cause the oxygen inside to deplete due to human respiration, while the carbon dioxide exhaled will accumulate. When the carbon dioxide concentration reaches a certain level, it can lead to unconsciousness and brain hypoxia, with severe cases potentially resulting in death. 2. Avoid sleeping in a car with the heater on: When the engine is running, incomplete combustion of fuel can produce high concentrations of carbon monoxide. If the car is stationary with the heater on and the windows closed, the carbon monoxide emitted by the engine will accumulate inside the vehicle, gradually increasing in concentration and making it highly likely for occupants to suffer from carbon monoxide poisoning.