Perhaps I should have known, but I have learned the hard way... When you
stop using dusty litter, you should remove all of the dusty litter
before adding new litter. I suppose it depends on the precise formula of
the dusty litter. If you don't remove all of the old dusty litter before
beginning to use your new less dusty litter, you can end up seeing
plumes of dust from the old dusty litter for a long time.