The way the object works now, there are really only two things that it can possibly do that harm people: freeze 'em, and burn 'em. The expansion on this with the reverse-effect thing is interesting, but that really leaves only three possibilities.
What could give it more content is if the thermostat could change the environment of the room as well— air density, moisture, the whole nine yards. That could give you more stuff to put in Addendum XXXX-1.
The addendum, I think, could be written like you said, except that the containment team isn't a moron squad. When they hear HQ saying 'leave now or you will burn alive', they haul ass out of there no matter what they're feeling— and only when they're outside the area of effect do they realize that a few of them have third-degree burns.
EDIT: I noticed that you put a - between 'Addendum' and 'XXXX-1' in the expansion. There's no guideline against that, to my knowledge, but I've always seen it with a space instead. For example,