I have my windows closed --as it keeps the road noise out also and I have my air set to recirculate -- except if I am country driving then I allow some fresh air in through the ventilation system  (unless on a dusty road)  I use my A/C all year

And to think a lot of the cyclists are doing it for their health.

Air pollution has dropped to unprecedented levels across the world as major cities and countries impose lockdown measures to curb the spread of the coronavirus.

The top picture shows the India Gate war memorial on October 17, 2019, months before the nationwide lockdown. The bottom picture shows the memorial after air pollution levels began to drop during the lockdown in New Delhi on April 8.

I'm doomed! I always drive with "recirculate" closed to ensure I receive "clean" fresh air on my face to keep me awake. Only use air-conditioner if necessary to keep cool or warm as appropriate. Windows are usually closed so I can hear the radio and/or ensure the a/con's efficiency when it's running. Rarely use the sun-roof in suitably mild conditions.

Depends on where and when. In slow moving traffic I keep the windows closed to stop the exhaust fumes from other cars to get into my vehicle. Would also use resurculate option. Why get bad air from outside through AC when you keep the windows closed to keep it out.

I use WD40, WINDOWS DOWN AT 40 K.P.H.

Never use recirculate - always fresh and a lot better than the toxic fumes off the interior materials .

Especially after the car sitting in the heat and these fumes building up inside!

We all know traffic pullution is bad, but have you ever noticed how many childcare centres are built on busy roads. Worst still, some are built at crossroads where there are traffic lights. The stop start of cars and trucks cause terrible fumes and brake pollution. I complained to my council once and asked why this was allowed to happen, they said that that was where the owners wanted them. I suppose for the exposure. Well the babies are exposed all right. Set up for sickness in later years.
And that was the end of it. 

REcirculate for longer than 10 minutes is just as dangerous as having so called dirty outside air coming into the car, it causes drowsiness and can multiply toxic and other fumes and some of your own exhaust fumes accumilating inside.

Check for yourself and see. drowsiness is a bigger killer.

I only use recirculate if vehicles in front are blowing smoke, if there is a dirt road and dust or bush fire smoke, after 10 minutes or less open to the out side air for a while, you will be alot safer.