[quote=@Lugubrious]
<Snipped quote by Lmpkio>

Thing is, no aliens work for the college.  Only humans.  A lack of oxygen can be handwaved in favor of sticking to this rule.
[/quote]

Yeah you can say that was the main reason. Humans cant survive due to the lack of oxygen so an alien that doesn't need much oxygen or breathes something that isn't oxygen can work.