Originally Posted by
Kendo66
Does this indicate some common fault in the type of air con system installed in the Helios jets? Was there ever any definitive answer to the reason for the 2005 crash?
Yes there was, and there was no fault in the air conditioning system. See this page for some brief details.
You'll probably get better answers later from those with technical knowledge - but airport air generally smells of fuel, for obvious reasons. The air supplied to the cabin is just drawn in from outside and pumped into the cabin. So it's no surprise when the air inside the cabin sometimes smells of fuel, too, when you're on the ground.