TGV lines have less tunnels, so making the trains airtight was less of a priority than for the German ICE. Still, though I'm not sure about what was built into the first generation and the TGV Atlantiques, from the TGV Réseau (the second subgroup of second-generation TGVs), they have a strong pressure isolation (for which is needed: double windows, isolation at car joints, and say pressurized air into the rubber bands around doors).

_{*Lunatic*, n.
One whose delusions are out of fashion.}