Can Foundation Personnel (other than D-Class) leave the site? Are there any necessary procedures first?

No, I'm not talking about retirement (though it's nice that they explained that), I mean can your average personnel leave the site? Do staff with homes or families nearby stay at their homes overnight when not needed, or is there a form or order that needs to be approved first? Or are you confined to the site and the field until you die or quit one way or another?