We know what helium and nitrogen gas do and what dangers they represent. We also know how much of them are in the LHC. The main danger is that both displace oxygen, so you can suffocate e.g. if a large amount of helium is released by a quench in a small room. But this isn't any danger to the surrounding area, there just isn't enough liquid helium or nitrogen in there.

Both gases are inert, so they really don't do anything else. There isn't anything to investigate here.