My oppinion is that ether smells mcuh more than THF, but form me is a familiar smell, not toxic, though it can go out of your appartment. THF smells less but is more toxic, smells much worse, fucks your liver and I hate it. Furanes are known together with dioxines as very polluting substances. I still have one liter and someday I'll try to make some lactone, for me is the best that can be done with it.