Here is my 100% Achievement Guide for Observation (Including ALL 85 Collectibles)
This is story related and cannot be missed.
After you find and follow Jim to UC-01 (The main big room). You will need to do a few things.. Lock all 3 doors and use the ventilation system (Although while we were busy locking doors, he could have literally just escaped but anyway..)
A cut-scene then happens which unlcoks this achievement.
Go to 2:37:55 to see the start of what we need to do to gain this.
Hope This Helps!