*This is a Metro: Last Light Achievement*
Near the end of "Facility" you will see a trap down a linear hallway (you have to go down the hallway for story progression.) It is hard to miss the trap, as the hallway has lights all over it. All you have to do is disarm it (press
near it) and it will be disarmed. reload last checkpoint and disarm it again. There is a save point right before you go into the hallway, so you don't have to redo much.