I'm wondering the same thing myself. In the second lab with the three floors you can go to the computer on the top floor to start venting the gas it seems, but I still don't know where you go to scan for the antidote.
Just found it. After you activate the computer I just mentioned you go down to the bottom floor where there's gas coming out of the pipes in the center column. Take your phone and look up at it and you should be able to scan it for the secondary objective. Hope that helps.