But of course at the right height breathable air is also buoyant on Venus, and that's one of the key things that makes floating habitats attractive - we can use air for lift and live inside the balloons, and thanks to the equivalence of pressure small leaks shouldn't be an issue. Multiple compartments plus some spare, un-inflated sections, and you can have decent redundancy.
(I am planning a book set in part on Venus, but it's book 6 of a 6 book cycle and I'm currently being very slow about finishing book 3)