Is unreferenced blob automatically collected by GC in firebird?

By unreferenced I mean it's not inserted to a table as a column in a row. So after calling isc_create_blob2 to create a blob I don't insert the blobId to a table. Instead I simply call isc_close_blob to close the handle.

If the answer is yes then what would happen if I don't even call isc_close_blob? The api guide says you should call isc_cancel_blob in this case or the storage space allocated for the blob will remain in the database but it doesn't explicitly clarify whether it's just temporarily kept in the database until the program that called isc_create_blob2 exits and will be collected by then or it's really stuck in the database forever.