Smell is organic, and the smell is there even when the AC is off as it's caused by a gas leakage from the evaporator. The smell will condensate inside the dashboard and then it would get through the vents and into the cabin as soon as you turn the ventilation or the AC on.
Several minutes after turning vent or AC on, the smell would fades away and becomes unnoticeable, until the next journey, the process repeats itself again and again...
if you want to make sure your AC system has no gas leakage, you can ask the dealer to put pressurise it and monitor it for 24 hours or so, if the pressure drops, then it's most probably the evaporator.
Last edited by rori zahr; 01-19-2013 at 04:31 PM.