They are not. BDC (bottom dual coils) do not have any ceramic/fiberglass in them. BVC (bottom vertical coils) do.
I find it very difficult to clean enclosed coils of any kind, including new Kanger BDCs. You could just do a "wet burn." Fill the tank (halfway or so) with 50%PG/VG and 50% vodka and vape this (without inhaling) until the tank is empty. Repeat if necessary.
Dry burning enclosed coils is not advisable--for many reasons. First of all, you have no control over the process if you can't see the coils. Also, without proper airflow you will almost certainly overheat and pop the coil. And then there is always some ash that needs to be evacuated somehow--very hard to to if you can't see it.
Thanks Birdie. Been waiting for that answer. I have the Aspire BDCs.