Is the 'a' button for internal or external air circulation?

[EmiliaLynn]

The 'a' button is neither for internal nor external air circulation. This 'a' button activates the automatic mode, where sensors will automatically determine whether to use external or internal air circulation based on air quality. The car air conditioning system is a crucial component in vehicles, differing from home air conditioners in that it features both internal and external circulation modes. During high-speed driving when opening windows is inconvenient, you can activate the external circulation mode. When passing through areas with heavy dust or during traffic jams, the internal circulation mode can be used. If external circulation is enabled during traffic congestion, exhaust fumes may enter the cabin. It's essential to regularly replace the cabin air filter during routine vehicle use, as failure to do so may affect passenger health and reduce air conditioning efficiency.