Do not call Destroy directly in an application. Instead call Free. Free verifies that the TIBBlobStream object is not already freed and only then calls Destroy. 

Destroy the TIBBlobStream object by calling Free when it is no longer needed for reading from or writing to the BLOB field. 

Destroy triggers an OnDataChange event if the Blob stream was used to overwrite or modify the data in the field. Destroy then frees any buffers that were allocated to handle the data.