Why can sleeping in a car with the air conditioning on be fatal?
4 Answers
Sleeping in a car with the air conditioning on can be fatal if the external circulation of the air conditioning system is not activated. In a closed car environment, a person may inhale excessive carbon monoxide, leading to oxygen deprivation in the blood and death. Below are some important considerations for resting in a car: 1. Avoid sleeping in poorly ventilated parking lots: If you must sleep in a car, ensure good air circulation first. If the surrounding environment has poor air circulation and the car is left idling, the carbon monoxide produced during idling can accumulate and fail to dissipate. If it enters the car, it may cause carbon monoxide poisoning, with potentially dire consequences. If you absolutely need to sleep with the air conditioning on, make sure to do so in a well-ventilated area. 2. Do not use the air conditioning's internal circulation mode: Besides avoiding sleeping in enclosed spaces, it's also crucial to pay attention to the air conditioning's internal and external circulation modes—a detail often overlooked. First, let's clarify the difference between internal and external circulation. External circulation draws air from outside the car, cooling or heating it before circulating it inside the car. Internal circulation, on the other hand, cuts off the exchange with outside air, merely recirculating the air already inside the car.
A few days ago, I heard from the security guard in our neighborhood that they had dealt with a similar incident—a guy slept in his garage all night with the car's air conditioning on. The key issue is that a running engine emits exhaust fumes, and since the car's undercarriage and trunk have limited sealing, colorless and odorless carbon monoxide can silently seep into the cabin. Modern cars now consume about two cubic meters of oxygen per hour, and the limited oxygen in a sealed cabin is far from enough. Last year, our city's hospital emergency department reported that over 80% of in-car accidents were related to sleeping with the air conditioning on. If you really need to rest, it's advised to keep the windows open for ventilation and avoid exceeding 20 minutes.
My husband works in the fire department and often shows us cases of people dying from suffocation in cars. Exhaust fumes emitted during engine idling can easily seep in through the gaps in the windshield. A carbon monoxide concentration as low as 0.08% can cause unconsciousness. What's even scarier is that electric compressors also consume oxygen. Last year, a newlywed couple rested in their car with the air conditioning on in the suburbs, and the carbon dioxide concentration inside soared to 15,000 ppm, nearly exceeding the human body's tolerance limit. Remember, even using the external air circulation mode carries risks, as the air conditioning intake is located near the engine hood.
A veteran mechanic with 15 years of experience reminds everyone: When idling with the AC on, the catalytic converter can reach 600°C, but exhaust treatment efficiency actually decreases. At idle speed, insufficient exhaust pipe pressure allows fumes to backflow into the cabin. Experimental data shows oxygen levels inside a closed vehicle can drop below 18% within half an hour - the human body's hypoxia threshold. Many owners mistakenly treat cabin air filters as life-savers, but these filters can't block gas penetration.
