Distinguished SOTW Member and Great Bloke.
Both require less air than a tenor in some ways. Think of a Bassoon as requiring warm air, lots of support hwere as on alto you can get away with slightly less solidity of air. This unfortunately is a double edged sword because in reality you need the same amount of warm air support for both instruments. Back pressure will also come into play here and this will be greater on alto than on Bassoon.