Well, guys: I'm beginning to regret having started this thread.
However thanks to all of your helpful links I now understand the principle and practice of 'inerting' fuel tanks on passenger jets and for that I'm very grateful.
I don't frequent PPRuNe very often and the main reason is the kind of stuff which has littered the rest of this thread culminating in the inevitable PPRuNe style name calling and sh*t throwing.
I have read the conspiracy theories with some interest and will leave you all to argue the toss.
Usually, when views are so entrenched in different sides of an argument no resolution or agreement ever ensues: It looks as if that's the way this thread is going.
Cheers
Cusco