Should You Use Internal or External Air Circulation When Sleeping in the Car?

[MarleyMarie]

When sleeping in the car, you should use external air circulation to ensure proper air flow inside the vehicle. If the surrounding environment has poor air circulation and the car is left idling while you sleep, carbon monoxide produced during idling can accumulate and fail to dissipate, potentially leading to carbon monoxide poisoning inside the car, which can have severe consequences. External circulation mode uses a fan to draw outside air into the car, meaning the air passages between the outside and inside of the car are open. The air blown by the fan comes from outside, and even if the fan is not turned on, air will still be drawn into the car while driving, replenishing the fresh air inside. Sometimes, you may feel airflow even when the fan is off, which is because the external circulation mode is set.