Some sources suggest recirc for heavy traffic -- I'd prefer a good filtration system.

And for rapidly heating or cooling a car, recirc can help. My preference is to open windows & sunroof (where present) to flush out hot air first, in hot weather. In cold weather, the heater won't kick in until the engine has warmed up, so recirc before that buys you little. And recirc + heat can result in fogged windows, so you may want to turn in the AC as well to rduce humidity. (Many cars now activate AC when defrost is selected.)

I rarely keep recirculated air set for more than a minute or two, most often far less.