Why can't they be washed??? Are you talking about silks etc??
I wash all of my quilts and hang them out to dry. I've bought some vintage quilts that smell funky and they clean beautifully. If I can't hang them I dry in very low heat (dryer)
Some get a good soak first and then wash.
I've never had a problem.
I'm talking about cotton here not silk or wool etc.
Let me know if I can help you!!
I really don't think products like Febreeze are good for quilts.
Just my opinion.
If I had one with fabric that you can't wash I would take it to a professional cleaner.
Also if they are fragile quilts I soak them only, wring out gently and dry either on the line or in the house.
Hope this helps