I'm surprised at all the people who want to keep it set to recirculate. Perhaps it's just because I'm in Silicon Valley where temps are almost always moderate. When I use A/C it's almost always because the temperature inside the car is higher than outside due to the "greenhouse effect" of the enclosed area, especially if I've parked it in the sun. So getting "cool" outside air (maybe 80 degrees) blowing in is more efficient and faster than trying to cool the 95 degree air in the "greenhouse." But maybe in Phoenix or someplace that's not the situation. Still, I remember reading in my Volvo's manual never to use the recirculate button longer than necessary, i.e. once the air inside is cooled down to a reasonable temperature, switch to outside air. This was described as being for health reasons. The car filtered the air through an activated carbon filter, I believe, or maybe a HEPA filter. The inside air supposedly contains chemicals and a buildup of CO2 if you are in it (i.e the CO2, or for some, tobacco smoke) and it is exposed to sun (the emissions from the upholstery, etc.) while driving. The filter either didn't engage the recirculated air, or didn't take out the CO2 or chemicals. I don't remember what the Leaf manual said, but I thought it was standard to use recirculate only long enough to get the temperature down. Pollution from the outside air is filtered out but not what you generate inside the car. If true, the default should always be outside air.
