Is it possible for an Chrysler 300 Touring Car to emit the smell of urine through the ac-heater vents even if the car's parked in a public lot but always with windows closed?

The air intack on most vehicles is located outside the car, mostly found in the "cowl" area. This is the area between the hood and windshield, usually a vent or similar. I am not familar with the 300, but most cars are set up like this. If the smell only happens on "recirculate" you might check the recirculation intake for your A/C and heater. It is normally located under the dash between the driver and passenger or under the front seats. Some accidents in these areas will cause an odor every time you put on Max A/C, but not (or at least not as noticable) on vent.