  We study the question whether disentanglement of Hawking radiation can be
achieved with any local operation. We assume that the operation we look for is
unitary and can be described by a Bogoliubov transformation. This allows to
formulate requirements on the operation of disentanglement. We then show that
these requirements can be fulfilled by a timelike boundary condition in the
near-horizon area and that the local observer does not notice the presence of
the boundary and does not encounter a firewall.
