Should You Use Internal or External Air Circulation When Sleeping in a Car?
3 Answers
When sleeping in a car, you should use external air circulation to ensure proper air flow inside the vehicle. Here are specific details about internal and external circulation: External Circulation: External circulation mode uses a fan to draw outside air into the car. Even without the fan running, airflow enters the vehicle while driving to replenish fresh air. However, during city driving in traffic congestion, the cabin may fill with exhaust fumes as this mode draws in polluted air from surrounding vehicles. Internal Circulation: Internal circulation primarily prevents external dust and harmful gases from entering the cabin. This is particularly useful when driving through smoky, dusty, or odorous areas, or in heavy traffic where it blocks harmful exhaust from preceding vehicles. Another function is maintaining cabin temperature.
Having driven for over a decade, I'm particularly meticulous about safety details. Never use the recirculation mode when sleeping in the car—it causes CO₂ to accumulate from repeated air cycling, creating oxygen deprivation risks. External air circulation is best as it brings in fresh air to prevent carbon monoxide poisoning. Once during a trip, I lazily used recirculation and woke up with chest tightness, narrowly avoiding danger. So remember: park in open areas, check that the exhaust pipe isn't blocked, crack a window slightly, set AC to around 20°C for comfort (avoid extremes), and don't idle the engine too long to prevent accidents. Your life matters more than saving pennies.
I believe health comes first when sleeping in the car, ensuring good air quality for comfort. The fresh air mode (external circulation) is the top choice as it brings in fresh air and prevents stuffiness. Internal circulation is only suitable for quick cooling in short periods and should not be used for long durations, as it can accumulate stale air and harm sleep quality. I recommend setting the temperature to 23°C and leaving a small window gap to maintain oxygen flow while reducing noise interference. As someone who regularly works out and pays attention to breathing, I find that fresh air mode with slight ventilation helps me sleep deeper and rest better.
