Quote Originally Posted by Portable Welder View Post
I wouldn't worry about the door opening outward, they should have a cell phone to call for help.
Except that a solid metal box buried in the ground probably makes an excellent faraday cage...

At the very least, make a smaller trap door in the main door that can open inwards and out of which you can poke the phone ... Or shout for help... Or just check that everything outside is ok

Frank