What is the emgergency, fire, slips or falls, being alone, assault etc. I agree make sure they sign in and have security check on them every now and then to ensure they are safe. Post the information onthe wall and if the security have a contact numbver put this on the notice so they can contact them if they need too.

Most Universities will have buildings open 24/7 where students can study. These will range from open access computer rooms to quiet study areas. These areas will normally be monitored by Security Staff or remotely by the use of CCTV. However if students need to study in buildings which are normal locked it was in the practice, in the university where I worked for many years, for the Head of Department to authorise this. The HoD would then provide the student with a pass code The students were required to log in with Security before entering and then on departing the building. In the event of an emergency the Security Officers would ensure the student had left the building. I would add that normally this permission was only granted to Post Grad students

I worked in a University for many years. In my department undergraduates were allowed in the library after hours; they simply had to be shown the night door. All undergraduates had also attended a meeting where the basic safety instructions were laid out (fire, first aid etc). Post graduates and staff were permitted to do laboratory work after hours. They had much more (compulsory) safety briefings. There were some provisos, such as they must not be alone, and there was some laboratory work that was outlawed out of hours. We had an electronic sign in system. The monitors displayed a list of who was in the building, updated every half minute or so.

Can access be restricted to certain parts of the building at all? When I was a student, and worked at the same university afterwards, the library was manned until 10pm ( except for exam time when it was manned by security throughout the night) and lecture halls/ rooms locked at 7pm. A reading room and a couple of PC Rooms were left open and were patrolled by security throughout the night. Direct dial phones to the security desk were in place should there be any problems- and details on notices in a number of languages. A lot of students do study better at night- if they have got "social gatherings" in the accommodation it can be a bit distracting, and also some international students struggle with the weather (generally the humidity in our case) and find it more comfortable to study at night.