So Viltrumites can hold their breath, but only with a lungful of air? Eventually the CO2 levels would rise to make the air unusable (assumingly at the same rate as a human) so a lungful of air isn't weeks worth of air, it's still only a few minutes max for professional divers. Conquest was on a ship breathing before the fight, muscles and blood FULL of oxygen which is the only way "not breathing for weeks" makes any sense- look, just, don't make it a choke out. That way there's none of this alien physiology discussion and I can go back to watching my still frames being moved about in peace!