With the setting to recirculate, the windows will probably fog up as if two teens were shagging in the back seat.

I always leave the fan on 1 minimum or above if I need to warm or cool quicker.

I adjust the temperature with the temperature knob, but always keep air circulating with the outside. I turn on the A/C to help defrosting when the windows fog up in the winter.

The only time I use recirculate is when I drive by the pulp mill or the oil refinery. Also when cleaning the system by spraying Lysol or other desinfectant in the cab air inlet for recirc.