I'm no lawyer, although that has never stopped me from debating legal
issues! It seems to me that it is unfair and unethical to expect an
unpaid volunteer to assume responsibility for safety and security in
such a situation without a regular, "official" staff member (paid or
unpaid) on the premises at the same time. Depending upon the
jurisdiction, I suspect that there might be some real problems of
legality and liability. --David Haberstich