Answer:
This situation was touched upon in a previous guru answer located at http://www.bankersonline.com/security/gurus_sec031703a.html.
A bank vault needs a ventilation system and the ability of someone trapped inside to contact the outside world. I suggest a telephone installed in all vaults and hidden from ordinary view. The reason to hide the telephone is to prevent a robber from destroying it if they decided to lock the staff in the vault.
First published on BankersOnline.com 1/3/05