Once you get to the hallway with the lockers, look into the closet for a med kit. Then, go through the door into the stairwell and silently go up the steps. There will be a guard with his back to you and another one pacing in front of a desk. There is also a camera on the wall across from the first guard. First, turn out the light in the stairwell. Then, sneak up behind the guard and grab him. Time this so that the other guard is going away from you and will not see what you are doing. Then, walk him while he is conscious into the dark corner of the room on the left. If you go all the way into the corner, you will not be seen by the camera at anytime. Knock out this guard. Next, shoot a distraction camera toward the wall directly under the camera or toward the darkness. Use the camera to make noise and when the guard is close enough, knock him out. Then, go down the hall and through the first door. Quietly go to the doorway. Use your night vision to see two guards in the beds. Shoot a distraction camera under the bed toward the head of the guard on the left and trigger the gas. Then, as the second guard gets out of bed, snipe him in the head. On the bunk on the far left is a med kit. On a table between the two middle bunks is pistol ammunition and a frag granade. Go up to the door to the room next to you, but not into it so you do not trigger an event. Us the thermal goggles and shoot out the light. Then, go back out the same way you entered and shoot out all the lights in the hall. Switch to night vision, open the second door, and two guards will start down the hall. Move back into the hall directly across from the double doors. Wait for the guard to open the keypad door. Once he moves just inside the doors, shoot the guard with the machine gun in the head (with the pistol if you have enough ammunition). Go just inside the doorway until the first guard goes upstairs. This will get you into the room without using the thermal goggle trick.