UPS generally does not radiate, but it is corrosive and the battery water is acidic. If the battery cover is loose, acidic substances will be released into the air. If you engage in that kind of work for a long time, it may do some harm to your skin.
PS: What unit are you in? Why has someone been in the battery room for a long time? Our UPS battery room and oil room are separated, so we can't enter people casually, let alone work in them for a long time, but we should check them regularly.